Isivili Enjiniyering
Fu n Getehn Engneeng More Candida Candidate te Academy news ProFilE oF MalcolM Jaros
April 2010 Vol 18 No 3
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2010 FiFa Wd cup 11 June – 11 Juy Isivili Enjiniyering
April 2010 Vol 18 No 3
Focus on Geotechnical Engineering
COVER ARTICLE W
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More Candidate Academy news PROFILE OF MALCOLM JAROS
i t a w S i S
oN THE coVEr Franki Arica, part o the JSE-listed Esorranki group, has again demonstrated its skills in providing geotechnigeotechnical engineering solutions in the marine environment, environment, this time in the construction o a temporary jetty and coerdam or the extension into the sea o Durban’s Sandile Thusi Road stormwater outfow pipe where Esor Arica is the main contractor
oN THE coVEr Franki Arica at sea again
oPiNioN
MarKET coNTriBUTioN
5
Are we jolly good Fellows?
ProFilE A bull terrier on a problem
2
Innovative soil stabilisation or road pavements
MarKET PErsPEcTiVE
6
Innovation takes place at the boundaries o disciplines
GEoTEcHNical ENGiNEEriNG Sivili Enjeneereng
March 2010 Vol 18 No 2
Block 19, Thornhill Ofce Park, Bekker Street, Vorna Valley, Midrand Private Bag X200, Halway House, 1685 Tel 011-805-5947/48, Fax 011-805-5971 http://www.civils.org.za
[email protected] editor
Verelene de Koker
BIGEN AFRICA asks: Are G overnment’s “Breaking
Using Atterberg Limits to predict the expansion o clays 12
Published by sAiCe/sAisi
Collapsible soils: an overview
New Ground” mixed-mode settlements addressing the housing backlog?
22
editoriAl PANel
Marco van Dijk (chairman), Irvin Luker (vice-chairman), Ali Naidu (SAICE president), president), Wally Wally Burdzik, Burdzik, Johan de Koker, Jerey Mahachi, Jones Moloisane, Hermien Pieterse, Eben Rust, Michelle Theron, Marie Ashpole, Zina Girald, Verelene de Koker (editor), Cathy van der Westhuizen (editor’s assistant), Barbara Spence (advertising), Dawie Botha (SAICE outreach) ANNuAl subsCriPtioN rAte rAte
SA R575.00 (VAT included), International US$ 122.00 AdVertisiNg
Smaller wireless Pile Integrity Tester unveiled Trenchless Technologies Technologies cc scoops SAST T award
Barbara Spence, Avenue Advertising
[email protected] [email protected]
Tel 011-463-7940, Fax 011-463-7939 Cell 082-881-3454 desigN ANd reProduCtioN
Marketing Support Services, Menlo Park, Pretoria PriNtiNg
The use o soil nails and mechanically stabilised earth in a road embankment across talus 40
ISSN 1021-2000 E N
H E R B L I S H P U S
Lateral support or Great Westerord extensions
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66
City o Cape Town leads the way
in service delivery
71
Updated permeable paving
design sotware available rom the CMA
saicE aND ProFEssioNal NEWs More courses rom the Candidate Academy New SAICE Fellow
Building Building the uture with the Geotechnical Division o SAICE – short course on problem soils 70 I you wish to reach the top, start at the bottom
Local retaining
block assists with upgrading o inormal
Identifcation o voids on the N1 North using ground penetrating radar 59
Eden Island – Paradise Engineered
Ash Resources launches “new
generation” cement extender
54
I
Z
school head
settlements
Ultra Litho, Johannesburg The South Arican Institution o Civil Engineering accepts no responsibility or any statements made or opinions expressed in this publication. Consequently nobody connected with the publication o the magazine, in particular the proprietors, the publishers and the editors, will be liable or any loss or damage sustained by any reader as a result o his or her action upon any statement or opinion published in this magazine.
Mining alive and well says new Wits
A green solution or the design and construction o steep slopes and embankments 46 Grouting – art or science? science? Procedures adopted at Changuinola, Panama
81
iN BriEF 83
Penetration testing: test procedures and design use in South Arica 29
[email protected]
Tel 011 805 5947/8, Cell 083 378 3996
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90
SAICE Photo Competition 2010 Diarise This
91
92
Access to Drat South Arican Standards
92
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2010 FiFa Wd cup 11 June – 11 Juy Isivili Enjiniyering
April 2010 Vol 18 No 3
Focus on Geotechnical Engineering
COVER ARTICLE W
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F O R E X C E L L E N C E I N M A G A Z I N E P U B L I S H I N GA N DE D I T O R I A L
More Candidate Academy news PROFILE OF MALCOLM JAROS
i t a w S i S
oN THE coVEr Franki Arica, part o the JSE-listed Esorranki group, has again demonstrated its skills in providing geotechnigeotechnical engineering solutions in the marine environment, environment, this time in the construction o a temporary jetty and coerdam or the extension into the sea o Durban’s Sandile Thusi Road stormwater outfow pipe where Esor Arica is the main contractor
oN THE coVEr Franki Arica at sea again
oPiNioN
MarKET coNTriBUTioN
5
Are we jolly good Fellows?
ProFilE A bull terrier on a problem
2
Innovative soil stabilisation or road pavements
MarKET PErsPEcTiVE
6
Innovation takes place at the boundaries o disciplines
GEoTEcHNical ENGiNEEriNG Sivili Enjeneereng
March 2010 Vol 18 No 2
Block 19, Thornhill Ofce Park, Bekker Street, Vorna Valley, Midrand Private Bag X200, Halway House, 1685 Tel 011-805-5947/48, Fax 011-805-5971 http://www.civils.org.za
[email protected] editor
Verelene de Koker
BIGEN AFRICA asks: Are G overnment’s “Breaking
Using Atterberg Limits to predict the expansion o clays 12
Published by sAiCe/sAisi
Collapsible soils: an overview
New Ground” mixed-mode settlements addressing the housing backlog?
22
editoriAl PANel
Marco van Dijk (chairman), Irvin Luker (vice-chairman), Ali Naidu (SAICE president), president), Wally Wally Burdzik, Burdzik, Johan de Koker, Jerey Mahachi, Jones Moloisane, Hermien Pieterse, Eben Rust, Michelle Theron, Marie Ashpole, Zina Girald, Verelene de Koker (editor), Cathy van der Westhuizen (editor’s assistant), Barbara Spence (advertising), Dawie Botha (SAICE outreach) ANNuAl subsCriPtioN rAte rAte
SA R575.00 (VAT included), International US$ 122.00 AdVertisiNg
Smaller wireless Pile Integrity Tester unveiled Trenchless Technologies Technologies cc scoops SAST T award
Barbara Spence, Avenue Advertising
[email protected] [email protected]
Tel 011-463-7940, Fax 011-463-7939 Cell 082-881-3454 desigN ANd reProduCtioN
Marketing Support Services, Menlo Park, Pretoria PriNtiNg
The use o soil nails and mechanically stabilised earth in a road embankment across talus 40
ISSN 1021-2000 E N
H E R B L I S H P U S
Lateral support or Great Westerord extensions
A
G
A
M
A
S
F
O
N
62
66
City o Cape Town leads the way
in service delivery
71
Updated permeable paving
design sotware available rom the CMA
saicE aND ProFEssioNal NEWs More courses rom the Candidate Academy New SAICE Fellow
Building Building the uture with the Geotechnical Division o SAICE – short course on problem soils 70 I you wish to reach the top, start at the bottom
Local retaining
block assists with upgrading o inormal
Identifcation o voids on the N1 North using ground penetrating radar 59
Eden Island – Paradise Engineered
Ash Resources launches “new
generation” cement extender
54
I
Z
school head
settlements
Ultra Litho, Johannesburg The South Arican Institution o Civil Engineering accepts no responsibility or any statements made or opinions expressed in this publication. Consequently nobody connected with the publication o the magazine, in particular the proprietors, the publishers and the editors, will be liable or any loss or damage sustained by any reader as a result o his or her action upon any statement or opinion published in this magazine.
Mining alive and well says new Wits
A green solution or the design and construction o steep slopes and embankments 46 Grouting – art or science? science? Procedures adopted at Changuinola, Panama
81
iN BriEF 83
Penetration testing: test procedures and design use in South Arica 29
[email protected]
Tel 011 805 5947/8, Cell 083 378 3996
72
90
SAICE Photo Competition 2010 Diarise This
91
92
Access to Drat South Arican Standards
92
89
79
1
ON THE COVER
Franki supports
the shtgun While many o ts cpttrs r t s w t cs t ptg succssu r suts, rk arc, prt t JSe-std esrrk grup, s ts t r t grud, succssu dvrg suts ts cgg vrt. S t cp’s st succssu ctrcts t st dcd r tst t ts . Ts prjcts cud t stt udts r spbudg d rpr rd, qu w d dr dck t Prt St lus murtus; t rs Ds mscrgs jb, s murtus, wc vvd jr xps t t xstg brtg cts; t Scs t u u Qu wr t qu ws xtdd r t 200 d b r t 1 800 ²; d t
ddg R213 rstdsgd Brt 208 t Prt Rcrds B. S, w t c t t pg d udt wrk r t xts t t s Durb’s Sd Tus (arg) Rd strwtr utw pp (kw s t ‘stgu pr’ bcus ts dub-brrd structur), t ws surprs tt rk ws skd b t tdrrg ctrctrs t qut s t spcst subctrctr r ts wrk. Utt t ctrct ws wrdd t esr arc, rk’s stbt t esrrk grup. rk dd t tprr wrks d pg 20 rs g, w t rg utw ws cstructd. i t 20 rs sc t ‘stgu’ ws rst cstructd, tr
v b sgct sd dpsts ts strtc bcrt, ctv vg t utt t dd t bc. Ts s cssttd ts xts bck t t s, t prvt stg-up d u rtr dg bck t strwtr sst. T bsc scp wrks ws t dsg d cstruct bt tprr jtt d crd c rd w t 5 g prtct w r t cstruct t xtdd ccrt ‘stgu’ ut. Ts tw crtc cpts t w r t cstruct t prt structur, but s sur ccss d s wrkg vrt r t ctrctr. “W t c t t tsk ds’t s tt cpctd, wrkg t c s bvus vr s d
2
svr ctrs cpct t prduct prcss d k ccurcs vr cgg,” ss mrc h, rk’s Durb dvs gr. T tprr jtt , k t ts ctrct , s 70 g d dd t b sufct strg t supprt tw trckd 80 t crwr crs. Ts ws cvd b stg 28 st tub ps prs r t gs c jtt sct. “T prcss rqurs gud r, wc sssts wt t pstg t ps, d t, wt t rgt qupt, t r std t t rqurd dpt,” ss h, ddg tt t cstruct butt t prvd t prtct r t s d ccss t t jtt trugut t prjct ws cvd usg st ps.
h xps urtr tt st tub ps r prps t st c r wrk s t v t dvtg s prvdg supprtg br t structurs ctd t s. Te teporry coerd ws but wt nterockng stee seet pes, nsted by usng te crnes postoned on te jetty. Tese pes were speccy procured to eet te exct specctons requred or t s job. “We cnnot tke ny cnces, bot durng te nucturng stge nd durng nst ton, s te entre re ust be be to wtstnd te uctutng nd sgn cnt orces o te ocen,” sys honn. “St st p ws r t st wd usd w t qus, jtts,
1
View o the sheet pile
coerdam prior to closing 2
Placing o sheet pile during
the nose cone construction
dr dcks, spws d structurs k t crd ts prjct. T r rtv gt d s t d d c b st d wd vrt s cdts du t tr w dspct crctrstcs.” T stp r rk t ‘stgu’ jb s t stt 72- 13 x 450 x 450 rrcd prcst ccrt ps, t supprt t xtdd ccrt ut c t prtct s rvd. uctur ts ps, esr arc st up cstg rd r t st, s tr spr tt
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4
The precast pile was one o the rst piling systems to be used in southern Arica. There is a record o their use in the now demolished old Putt Bridge in Port Alred, where back in 1908 the precast piles were installed using a steam-operated piling machine suc rg ps vr dstc wud v b ucc. “Tese pes ve te dvntges o beng cst n controed envronent nd wy ro ny dverse condtons wc coud be concern or ny cst-n-stu pes. Tey so provde n econoc souton or tese so condtons nd t er nstton does not rey on te ccess requreents 4 Civil Engineering | April 2010
tt cst-n-stu pe woud requre,” expns frnk contrcts nger mttew Cck. T prcst p ws t rst pg ssts t b usd sutr arc . Tr s rcrd tr us t w dsd d Putt Brdg Prt ard, wr bck 1908 t prcst ps wr std usg stprtd pg c. d t uctur ts ps s dvpd t stt t rt prcss. “T k t succss ts prcss s t qut t ccrt,” ss Cck. “it s t b t gst qut d trr t ggrgts ust s b t bst qut. i ddt, t 28-d strgt t ccrt s r t 50 mP d trr t ct ctt ust b t st 450 kg pr cubc tr, wc gvs s d t qutt ct dd r t jb!”
3
The nose cone ulilling its purpose
4
The precast piles ready or installation
T prcss s st cpt, wt t prcst ccrt ps st t b std. ovr, h s psd wt w tgs v prgrssd. “W v xct d tvtd t w v c g dstrtd rk’s uqu sks t r vrt wr tr r uqu cgs. W wrk fct, wt vr g rgrd r t st ur ps d t pubc t prduc, tgtr wt esr arc, wrd-css rsut.” INFO Tammy Davies Esorranki Ltd 011 822 3906
[email protected] www.esorranki.co.za
Dawie Botha SAICE Outreach
[email protected]
OPINION
Are we jolly good
Few? a Common ComPlain rsd t vr strtgc sss vr grg sttut t wrd s: “W ck sttus. W r t rcgsd.” T qust t rss: W s sttus s prtt, d sttus s s prtt, w r grg prsss s trgc w t cs t crrg r rcgsg sttus tt s b du rd? m prcpt s tt, tug w scrt r r sttus r ursvs, w r tt t t rcgs ur w grg prsss r wt t v cvd. W s s w r t pprprt d prct g rgt t c ursvs egr r cgst r cc, tug t s gr ccptd s crrct t ddrss pprprt prss s Dctr r Prssr, trb pg d rspctg tr sttus. at SaiCe nt ofc w r t u tg tt “Brcs d Dvss d t subt ts r ws”. hw d w r rt? T arc Sct Cv egrs rcks tt t sud v but 7% tr brsp s ws. W r t 4% – t cprb pctur. hs t crrg w sttus bc d-sd dr wrd “rd-equt-
Brtrd”, à J-Jcqus Russu? i bv no. ev ts dr wrd dc prcttrs r usu ddrssd s Dctr, d st prts arc g rs ddrss tr s egr s-d-s. But t us gt bck t SaiCe ws. our excutv Brd s cg ur brs t subt ts r ws, s tr r dsrvg dvdus ut tr. cr t sttu s w cgu d pr s prvg, d v b bgt. T dd r 2010 SaiCe w ts s 31 Ju 2010. lt us rcgs ur t brs. ad u r dvdu w s t b tcd b trs, t ps aPPly! k crg. i ccus, t us c r dvur t strt grud sw b t st sgg ur s s egr. lt us trduc ursvs s egr, c ur cgus egr w w t t fc cpct, spc pubc d tgs. it b dfcut t rst, but t ssur u, t bcs tur tr w. Bst wss egr, cgst d cc Brw, St, D d V dr mrw! Eng Dwe Bth, Few saicE
Lorraine Fourie
[email protected] 012 343 1434
PROFILE
a bu tee
on a problem sHarPENiNG THE FacUlTiEs
1
A career that saw Malcolm Jaros leave his geotechnical footprint on five continents was rightfully acclaimed on home soil recently. Not only was he lauded the winner of SAICE’s Geotechnical Medal in 2009, he also received GIGSA’s (Geotextile Interest Group of South Africa) biennial award for technical excellence in the same year. What contributed in no small way to success is his ability to focus totally and passionately on the issue at hand – “I’m a bull terrier on a problem,” he says. This skill has a flipside: a certain vulnerability when it comes to socialising. “I’m what you might call socially challenged,” he admits ruefully. In conversation, Lorraine Fourie found Malcolm abounding with enthusiasm about his work and the eventful course that his life, with his wife Paula at his side, has taken
mc’s pwrs cctrt wr dvpd t sc Buw, wt ws t Sutr Rds, wr xcd sw g. “W u’r spdg urs vr d wt ur d udr wtr u r cusd tg . T dwsd cpttv swg s tt t s vr tsc sprt,” ss. h ws sctd r t Sr R Wsk’s drt t, prtcptg t brst-strk vt, but tr cc ccdt wc dgd s sp, ctv sd s swg crr. o sg s scg mc t wtd t bc ctrc gr, but t t Uvrst Rds d nsd d d t r grg. Wt s grdprts vg Jsburg, t ws cvt r t st wt t w ttdg t Uvrst t Wtwtrsrd, wr rd r BSc cv grg dgr 1964. lk s studts s r mc ws sprd b Pr Jgs, d s trst gtcc grg grw std udr t gudc s tr. Bcus wrkd u-t vr trt r, t tk sv rs t cpt t ur-r dgr curs. “i dd’t cr wt kd wrk i dd s g s t pd gd , d t gst pd jb t st utsd rs ws s cputr prgrr, wc ws qut v tg ts ds.”
W grdutd d dgr grg s w s xprc s crc cputr prgrr. h tugt ts wud c usu w ppd r jb t ov arup & Prtrs. “i ts ds vr w grg csutts d cputrs d arup srd wt tr tr rs Jsburg.” hwvr, s bss ws t p tt u cud t b bt; t ws tr t r t tr, s mc ws t pptd s cputr prgrr, sttg up t dt prcssg sst r Cvb. “arup ws t wrkg t C rt Ctr d t dd t prcssg s tst rsuts t b uttd,” xps.
cptd mSc (s c cs) dgr r ld Uvrst tgtr wt dp udt grg r ipr Cg. as t Jrs’ prpsd rtur t Sut arc ccdd wt t 1976 Swt rts, mc ws rd xtdd st ld. Brg tr tw s cdr d, tkd t vr wt Pu, w s Brts ctz br hg Kg. T jt dcs ws t rtur t Sut arc. “i just cud’t std t d vg suc w-rdrd sct; i wud v dd brd. arc, spc Sut a rc, s wr tgs r ppg,” ss wt c vct. 2
FailUrE NoT ParT oF His lEXicoN as gr--trg wt arup, mc rst xprcd t prbs dsgg udts r structurs udrd grud, tpc tt ws t rvst tr dc ds tr r t Gutr prjct. hs rst sgct prjct ws t ppct t et ass t dsg t dck sbs d br gs r t pr brdgs tt crr t n2 rw vr t Kwmsu-Durb r . “at t t t wr t st cut skwd dcks ttptd Sut arc – t g trsct btw t trw d t r w s 23. i d’t tk i r udrstd t w sgct tt ws. nw, tr t v std tr r 40 rs, t c vr usu r rbuttg scptcs w wt t kw w ud cc s tcg structur grg,” mc, ws spcst d s s structur trct, ss wt qut rt. grdut trg prgr cutd wt 30 -t stt t cp’s ld c. Gg brd wt wr s w Pu, w d rrd 1968, d t-t-d d adr ws sstr ld ws br w ts tr t rrvd egd. r, mc gd xprc t dsg d cstruct pd udts, dp bsts, rtg ws, udrpg d tug, w s cputr prgrg xprc prvd vub t prcssg dt r t hg Kg ss trst r sst. ‘Wrkg s butt ’ bcus t ws ut kb, s
1
Malcolm Jaros receives SAICE’s Geotechnical
Medal at the Geotechnical Division’s AGM in November 2009 rom Dawie Botha, SAICE Executive Director at the time 2
With a Czechoslovakian ather and
a Kenyan-born British mother, Malcolm Jaros turned out proudly South Arican 3
Malcolm’s son Adrian (let), daughter-
in-law Venus, and Malcolm and his wie Paula holding Muin, their Yorkshire terrier
3
EVEr BroaDENiNG THE scoPE
In the early '80s Malcolm rejoined Arup "who had some very interesting projects under way in Natal. The King Shaka Airport (hard to believe that it’s only just been completed), the Nkosi Albert Luthuli hospital, as it is now known, and the redevelopment o the Playhouse Cinema as the Opera Theatre were challenging prospects. The basement excavation o the Playhouse, at the time, was the biggest and deepest in the Durban CBD, going down 6 m below sea level, and we nervously measured water levels and ground movements there throughout construction.” Also careully monitored or ive years was the settlement o the 27-storey Beachront Holiday Inn, the tallest building constructed on estuarine Durban harbour deposits without the beneit o piled oundations
Bck Jsburg mc vd t arup’s gtcc grg dvs wr dd st vstgts d dsgd vrus pd udts d tr supprt ssts. atug d spt s t ts 1971 wt Bs Rd s prt xcg prgr t g ctrctg xprc, mc t dd bttr sgt t t ctrctg busss, spcc rt t pg d gtccs. “S i jd mclr & egr P g t udrstdg tt t wud b r tw rs .” h t, wt s rg tt, ssug t r ssct t w-rd Wbr & n csutc, wt w std ut 1983. mc ctus: “i t rjd arup w d s vr trstg prjcts udr w nt. T Kg Sk arprt (rd t bv tt t’s just b cptd), t nks abrt lutu spt, s t s w kw, d t rdvpt t Pus C s t opr Ttr wr cgg prspcts. T bst xcvt t Pus, t t t, ws t bggst d dpst t Durb CBD, gg dw 6 bw s v, d w rvus surd wtr vs d grud vts tr trugut cstruct.” as cru trd r v rs ws t sttt t 27-str Bcrt hd i, t tst budg cstructd stur Durb rbur dpsts wtut t bt pd udts. T rsuts wr wrtt up wt dts t udt dsg ppr tt rd , tgtr wt Gr Pt, Gv Br d C mcm, t Jgs awrd r t bst tcc pubct 1988. Sttt surts tr structurs cudd t rt-supprtd gt-str budgs t Stv Bk cpus t Br r wc mc d b, s ds t mclr & egr, t st vstgt ctrctr. T stt, prtct d rdg ts trg ssts grt cd cdc t dsg tds usd d ts xprc tr prvd vub prjcts suc s t hg Kg rprt rct d t udts t rc r t mss mbd stdu. W arup dcdd t cs dw ts Durb fc mc std w t t cp, cutg wk r svr ts btw Durb d t Jsburg d fc. “W dd’t wt
t dsrupt t cdr’s g-sc duct. Bsds, w’d rd vd r t dz ts ur rrg d wt Durb t pc wr w’d vd gst w wtd t k t ur .” l mr, mr Spc Js (mSJ), tks up t xt squc vts mc’s : “at t t mSJ ws st dgg t csutg dustr, but w d b gv rg tr supprt prjct r t t Durb Ct egrs’ dprtt. g dcdd vurb d dg supprt, i cd mc, w t w, up t t, i’d d br ctct. Wtut stt sd, ‘Brg t ’, r stg t tt ct. it ws t strt trust g wrkg rtsp wt w t xps st, tgrt d ddct cpssd prsss. i tk mc kd us, r jd mSJ s drctr 1989.”
DisTaNT HoriZoNs BEcKoN W, 1994, ttrctv jb r r t dvpt t t w Ck lp Kk rprt hg Kg c s w, mc cud’t rsst. “nt ws t tstc prjct, but t cdr wr b w kg w vs r tsvs w r . it ws s r Pu rtur t r brtpc wr r prts d b sttd wt t Brts r,” ss. Wt t ws trt ctrct xtdd t tw rs d vtu tr. mc ws vvd ctrg d surg sttt t rct r t rprt t sur tt t ruws wud b st d t w cssd d tt t wud r srv cb cdt r t st sv rs br vg t udrg jr tc. ”Ts ws w tcc r r , but i jd t s.” Durg tr hg Kg st t cup d t pprtut t vst austr svr ccss. Brsb ws t ct tt d udd Pu d s ws t gg t t t cc pss b br tr ctrct xprd. o gt mc, rturg r fc, rcvd p ssg sg: “yu’v gt t c t Brsb; tr’s jb r u r wt C Gtccs.” “S, tug t p ws t rtur t Sut arc, t spur t t w dcdd t g t austr. T rd tw-r ctrct d i guss t t bck ur ds tr ws t d strtg
sudrstdgs d wrk wud sz up. But u wtd t gt tgs wg g u d t gt Sut arc tr. Sut arcs just v t sprt, t ‘br k ‘ p’ tttud.”
4
coNTriBUTiNG To HiGHEr lEarNiNG
w Brsb.” atr r, mc d d ug austr. C suggstd tt tk s v, v k t t stut bck Sut arc d t k dcs. “i dd tt, d i rsd tt ts ws wr rt .” h w bck t d s rsgt d rturd t Durb Ju 1999. T st Pu, wvr, sd, “W’r r tw-r vs, s i’ vg tw rs’ wrt”, d std t t d ’99.
FoUNT oF EXPEriENcE oN HoME soil mc rjd mSJ s prcp gtcc gr t udrstdg tt wud b pd strct csutg cpct wtut gr rspsbts. “i c bck t t tck trsrt Sut arc d i dd’t v cu wt Bee ws but. at tt stg i just wtd t d tcc jb.” l mr ss t t rs t wrkd tgtr: “ d g mc wud sr s s rsrvr kwdg wt s cgus d p t sp d grw t prctc.” Ts vst xprc c t t rscu w ws cd up t brk gj t Gutr prjct. mc gvs t bckgrud: “o cg t ssu tkg t rw trug Sk V, t sk r rt Ctur, t prdt rc grs w rprstd t ctrctr sw t s just tr rsk gt prb, wrs Sut arc grs tdd t ctr tr prs xprcs t csqucs
sk cps. T rsk t d b vr w rsrcd d qutd, but t dts w t d wt t d’t b u rsvd. “Sw i ud s pst btw t ctrctr d t supr vsg grs, but gd t s bt sds t rgut d dvpd sut tt ws ccptb t prts. Rrcg wt gtxt sts t bkt wc t trck wud ru – tr dc cpct t udrg grud – wud w t ccrt U-b t supprt t r- vr t dgr r ts rg dsg r, tt s, s prptu brdg crss ptt sk.” Ts put rd mc t GiGSa wrd 2009. “ s xtt vvt Sk V ws t g t tgs tt i’d rt crr: s structur trct, s btw t U-b d t grud; grud trtt, s t prcss dc cpct; d sttt ctr, wc i’d dd xtsv hg Kg.” Urvg dsputs s t u r t mc. h rcs w d t srt ut psss hg Kg. “Wt austrs, arcs, Cds, pp r t d ir Curt cutrs, wstrsd hg Kg Cs, d Cs, wrkg t prjct udr Brts ctr, t ws crdb cpx cutur xtur. T dvrs bckgruds, stdrds, d ws dg tgs t cusd
i apr 2008 mc xcgd t csutg busss r cd. “cc i w t d t quvt t hg Kg d Gutr prjcts g – s i dd t d w cgs. Trug vvt wt t Uvrst KwZuu-nt (UKZn), s prt-t xtr xr gtcc grg sc t r ‘90s, i d s t grppg wt t trsrt prcss. But i s sw tt t d dt p d wr wrkg twrds g t k t wrk. i wtd t b prt tt p bcus t ws w pprtut t k uc r gu d s tsg ctrbut t wt i rsw utur s csutg gr.” W mc jd t UKZn cv grg dprtt 12-t tprr ctrct dt bc vvd pg t dprtt ddrss eCSa’s rqurts trs t Wsgt accrd, wc surs tt Sut arc grg dgrs r rcgsd vrss. “W wr t rst grg dprtts t Sut arc uvrst t gt u v-r ucdt ccrdtt r eCSa r dstrtg cpc wt tr rct trsrd utc rqurts.” mc w b vvd u-t r t xt tr rs d ps t v s ctrct xtdd t sx rs. “lk Pr K Kgt i c s s vvd w bd rtrt. Br i strt dg w, w w v rvgrtd t pstgrdut curss d rsrc ctvt tt r t sst cpts uvrst.” o t sx dctr cddts w rd t UKZn’s pstgrdut sc cv grg s mc. “ qup bttr i v t g trug t prcss s d rcrut str’s studts t grt rsrc ts.” T t s dctr tss ts r t Gutr prjct. “i cud’t just d s stud s dspsst subjct – i’ ctv w i’ psst vvd, wc s wt ppd t Sk V prb. i bv tt t sut w prducd ws t rgt , but bcus t ws t rst ts kd tr r ts
t trtc bckgrud tt i d t b xprd. m rsrc s drctd t w t prv t trg prcss t urtr rduc rsdu rsk tt b rt t sut.”
Designing or contractors requires a very special breed o engineer and
GEoTEcHNical iMPriNT – 2010 aND BEYoND
below, with post-construction delections o less than 20 mm. With
i s ds wt ov ar up, mc dd dsg wrk r wt ws t rkp d tr, w ws wt mSJ, r esr w dvpd t t prst-d esr-rk. st rct d g-pr prduct ts rutu cbrt s t t mss mbd stdu Durb wr esr ws wrdd t ctrct r t udts r t r-supprt rc t bss mc’s dsg. Ptr D, s dpdt udtr, ws b t gv t Gr dsgrs t rc t ssurc tt tr sdr cstruct wud t b dstrssd w b udt vt. Ptr ss mc’s dsg: “Dsgg r ctrctrs rqurs vr spc brd gr d mc s t crdts. T cg cd ws t trsr t 100 mn rzt trust xrtd t t rt d t rc trug 20 sturtd sdts t t wk Crtcus udsts bw, wt pst-cstruct dcts ss t 20 . Wt s crctrstc tct, mc dsgd 42 x 7 dprg w ‘bx’, t sds wc ctd s dp sr ws. Ts ws t rst jr gtcc dsgs Sut arc t b crrd ut ccrdg t t eurcds, vvg bt t qubru ss d tr-ds urc dg. its succssu ptt, wt tt vr t prttd vt bg surd, ws sufct t w t SaiCe awrd r cc excc 2009.” Judgg r s tst cvts, mc s vr g w r dg ut t gtcc sc. h s, t qut l mr, “ r sss, d gd xp t w.” 4
The team employed by Esor to
design the Moses Mabhida stadium arch oundations - rom let: Pieter Boorsma, Lionel Moore, Mark R ichter, Peter Day, Malcolm Jaros, and Arthur Field (Director, Esor) (Photo Tony Smith – copyright protected) 5
and
6
The Moses Mabhida
stadium with arch intact (Photos Tony Smith – copyright protected)
Malcolm has all the credentials. The challenge he aced was to transer the 100 MN horizontal thrust exerted at the north end o the arch through 20 m o saturated sediments to the weak Cretaceous mudstones his characteristic tenacity, Malcolm designed a 42 m x 7 m diaphragm wall ‘box’, the sides o which acted as deep shear walls. This was one o the irst major geotechnical designs in South Arica to be carried out according to the Eurocodes, involving both limit equilibrium analysis and three-dimension numerical modelling. Its successul implementation, with little over hal o the permitted movement being measured, was suicient to win the SAICE Award or Technical Excellence in 2009 5
6
Prof Dereck Sparks Emeritus Associate Professor of Foundations and Soil Mechanics University of Cape Town
[email protected]
GEOTECHNICAL ENGINEERING
Ung attebeg lmt t pedt This article describes a method for predicting the expansion of clay which is supported by measurements on a wide variety of clays. If a small building load is applied to a clay in an arid region and the clay is subsequently soaked with water, this building load will not prevent the clay from swelling. But if the same clay is subjected to the same building load in a wetter climate and is subsequently soaked to the same condition, then the new building can settle. Calculations are provided to demonstrate this phenomenon. The article contains simplified extracts from a paper describing the wider general topic of modelling of clays (Sparks 2010). The method described here shows that only two equations (namely Eqs (8) and (9)) are required to estimate the expansion of a wet ted clay
iNTroDUcTioN T vu cgs cs du t cgs wtr ctt r cs rtd t t udg d rdg curvs c subjctd t strpc dg (.g. strpc dg c b cusd b t c prssur ppd t jcktd s sp trx c).
isoTroPic coNsoliDaTioN gur 1 ustrts sturtd c sp wc s drg (t t tspr) brtr. T pr wtr prssur s vu u kP wc s gtv (wt rspct t t tsprc dtu). at ts stg t s prtt t udrstd crt prcps rtg t t rzg ctv st rss qut r sturtd s (eq 1): t strss p = ctv strss p’ + pr prssur u
(1)
i eq (1) w v tw drt pts. W c xprss t tt strss p d t pr prssur u bt wt rspct t vcu s t dtu, r w c xprss t tt strss p d t pr prssur u wt rspct t tsprc prssur. T vu t ctv strss p’ w b dtc bt ssts. W usu prr t xprss t tt strss p d t pr prssur u wt rspct t tsprc prssur (.. t pr prssur u s qu t zr t t v wtr tb). i druc pp ssts subjctd t g sucts, t wtr w cvtt (.. vpur bubbs r d grw) bcus udssvd r cus xst t wtr d ts r t uc r t rt vpur bubbs. hwvr, cs t pr wtr s bsrbd t t c prtcs s sprt wtr cus d tr r usu udssvd r uc t pr wtr. r ts rs t pr wtr cs c b subjctd t vr g tss wtut t rt vpur cvts. i ct Dx (1909) ud tt wtr c wtstd ts strsss vr 160 tsprs (16 000 kP) tr r udssvd r uc t wtr. i gur 1 t tt strss s zr trugut t drg prcss t sturtd c. i t tt strss p s zr eq (1), t t ctv strss p’ s pstv d s qu t (-u). T ctv strss p’ crss ts
the expnn f y pstv vu s t sp drs ut, d ts cuss t sp t dcrs tt vu. T utr prrs t c ts ctv strss u*, c gur 1 u* s qu t (-u). i gur 1 t r-wtr scus surc cts sr s t t rubbr br wc surruds t s sp gur 2 . i w cprss t sturtd c gur 2 g vrg cprss pt w t ppd rzt strss s qu t t vrtc ctv strss, t w wud xpct t strpc cprss curv t b dtc t tt ud r t c gur 1 (vd rt vrsus vrg ctv strss wt t sp). But w ws t stt t vd rt w t rzt strss s t qu t t vrtc strss gur 2, t w rst d t d t vrg ctv strss gur 2 wc s qu t p’ = (p’ v + p’ + p’ )/3. W c w tr t strpc cprss curv btd r gur 1 wt ts vrg vu p’ (r gur 2), d c bt rsb pprxt r t vd rt t s gur 2 .
sUPErPosiTioN oF sUcTioN aND EXTErNal aPPliED sTrEssEs a sp ctd t s dpt t s cud b subjctd t pr wtr suct (-u) s gur 1 d s t psd strsss’ v d ’ (s gur 2) wc r cusd b t wgt t vrburd r b strsss r udt bv ts sp. T ct u d t ct du t t ppd strsss r bt ctv prssurs, d c b ddd tgtr. T cbd vrg ctv strss t sp du t bt cuss s u* eq (2). 1
Saturated clay sample permitted to dry out to the
atmosphere in the soil laboratory (isotropic consolidation) 2
Drained sample in rubber jacket in triaxial cell
u* = (u du t pr wtr) + (p’ v + p’ + p’ )/3
(2)
i t s sp s b cprssv (ctv) pt, t p’ = K.p’ v wr p’ v = ctv strss t vrtc drct (.g. du t vrburd). T utr usu u ss K = 0,4. hwvr, t s s b swg (pssv) pt, t p’ = Kp.p’ v T utr uss Kp = (2 + 200/p’ v ) wr p’ v = vrtc ppd ctv strss (kP), but t xu vu r K p s tk s 6. T utr ccpts tt K p c v b s g s 10. i st stcs, tr s tt drc t swrs vu 6 r vu 10 s usd. W t s sp s brugt t t brtr, t s kw tt t w t r t xpd du t t rs t prssurs p’ v d p’ . i t sp s dd ccss t r wtr, t t s suggstd tt t vrg ctv strss t s 1
2
.Pore Pressure u (-ve)
σ’v
σ’
h
sp s ucgd d st r s s u* (gv b eq (2)). i tr wrds, t vu u* t brtr st rts t r u* s t d. a cpt ts r cuds t psd ctv strsss p’ v d p’ wc ctd t d.
aN ElEMENTarY EXPlaNaTioN oF HEaVE Csdr s sp wc s t t stt X t BD gur 3. i t ctv strss s rducd, t t sp w sw r stt X twrds t stt D. Sr, t pr wtr prssur u bcs r pstv, t s sp w xpd r t stt X twrds D t s BD. T qudt dx, li, ws dd b Skpt d Bsp (1950) s:
4
3
A
A
0,301
Liquid Limit
li = (w% – Pl%)/(ll% – Pl%)
Straight Line ) I L
% w t n e t n o C r e t a W
D
D
+ 1 ( g o L
X
X B
B
E
Plastic Limiit
0
C
C 6,3 kPa u*=R x 8,9 kPa
Log u* (kPa)
Log u*( kPa)
5
D
wD
X
wX
f o e u l a v y . l b l e d e w s n f i o m D t r t i e t a m e * i L D u
t n e t n o C r e t a W
1 kPa
10
u* D
B C
u* X 100 kPa
1 000 kPa
10 000 kPa
Log u*
6
Liquid Limit
t n e t n o C r e t a W
Plastic Limiit
D1
X1
D2
(3)
nt tt li s r uct w%. it s trr s t us li g t vrtc xs gur 3 std w%. i rdr t d cs vr rg rg qud ts d pstc ts, t utr s trducd prtr R (Sprks 2010, prss ) wr: lg R = (Gs.Pi%)/{0,918 (ll% -5,7)}
(4)
T vu lg R s usu pprxt 2 r c, d c R s pprxt qu t 100. hwvr, r s cs R c b s w s 45 r s g s 180. T Sprks 2010 ppr s trducs t prtr lg (1 + li) r t vrtc xs s gur 4. T us lg(1 + li) tks t ccut t curvtur t aBC gur 3. at s stg t pst t c ws prcprssd t t stt B g t cprss curv r a t B gur 3. s c cc ur du t dscct r xtr dg (.g. wgt c st). rtr t v u u* ws rducd b wttg t s p r b rduct t xtr ppd dg. hc t stt t c vd r stt B t ts prst stt t X. a gr wud k t kw w uc urtr t c sp c xpd. i tr wrds, wt s t sw wc crrspds t t rduct u*, .g. du t wttg (r stt X t stt D gur 5). T gr ust dtr t wg: 1) T sp t BD. Ts s s t stbs. 2) T pst t pt X, .. t suct u* x d t wtr ctt w x. 3) T suct u* d t t stt D. Ts s rtv s t stt. T bv wud prt us t drw t dgr d BD gur 5 r ts c sp.
Wilting Limit
X2
3
Shrinkage Limit
ABC is the isotropic consolidation curve – the sample
precompressed to B can swell along BD and point X can be the present state o the sample prior to swell 4
Log (1+LI) replaces w%. T his plot gives straight lines. R is dened in the text
5
This is an enlargement o a portion o Figure 4. This
gure is important to understand the swelling process u* D1
Log u*
6
Note that the slope o the swelling curve is the same at X 1 and X2,
hence the same equation (Eq (8)) can be used on either swelling curve
T cg t bv st s t stt t suct u*x prr t t wttg t sp. o td t d ts s t pc Wt’s n 42 tr ppr drct ctct wt t st s sp r-tgt btt r tw wks. msurg t wtr ctt t tr ppr ds t stt t trc suct t s. hwvr, tr pprxt trtv tds xst r sttg t suct prr t wttg. assu tt t wtr ctt w x% t s t stt X t rbud curv s kw, d s t suct u* x (kP). T utr suggsts (Sprks 2010 ) tt t curv BD gur 5 c b dscrbd b eqs (5) d (6):
ur tr sw (suc s t stt D). Ts s crrct ccpt. a “ t sw” s t prprt t c. Csdr sps c wc r ctd t drt dpts wt t s . T cg prssurs d sucts tt xst ts sps w vr wt dpt. T sp tt s swg g t X1 t D1 gur 6 w sw up t stt D1, d t pst pt D1 s dtrd b t vu t quvt suct u* (.. t ctv strss) wc xsts t stt D 1. T t sw t stt D1 s t prprt t c, but s dtrd b t vu u* D1 wc xsts t stt D1 (s ccutd b usg eq (2)).
w% = w x% + {C.Pi%/(a.lg R)}.(lg u*x – lg u*)
coMParisoN BETWEEN THEorY aND PracTicE
(5)
lg u* = lg u* x – {a.lg R/(C.Pi%)}.(w% – w x%)
(6)
r spct w us C = 1,6 d a = 6
(7)
b 1 sws cprs btw surd sw prctg (s surd b Scrr 2008), d t vus ccutd b usg eqs (8) d (9). it ss tt Scrr prttd t sps t dr t brtr rtc dr tspr s tt t sps bc drr t t srkg t. h s t pubsd t dr wtr ctts ts sps. hwvr, t s kw tt t tt vu c sp w crs w t wtr ctt crss bv t srkg t.
r eq (5) t c b s tt t cg wtr ctt durg t sw s gv b eq (8): wc% = 0, 266 {Pi%/(lg R)}.(lg u*
– lg u* )
EXaMPlE 1 – UsiNG scHrEiNEr’s claY (sa-13)
(8)
Scrr’s tsts wr prrd s sps wc wr t prt sturtd. as rst pprxt, t bsc tr rt, c us t srkg t wtr ctt s t wtr ctt r wc vu crss w ccur. T wtr ctt t t srkg t ws srtd t eq (11) (s appdx) rdr t stt t strtg suct u* t t srkg t. r xp, r sp Sa-13, t suct prr t wttg t t srkg t (10%) s 4 935 kP. Scrr sttd tt t vrtc strss t t d t wttg prcss ws qu t vrtc dg 15 kP d tt t sp ws dd s tt t pr prssur u ws w zr. Usg eq (2), t quvt vu u* t t d t swg prcss c b sttd (t vu u* s 43,3 kP).
wr u* = quvt suct prr t wttg (kP) d u* = quvt suct tr wttg (kP). (S eq (2).) T rg wtr ctt w % t s prr t wttg s kw. hc c wrk ut t prctg sw pr ut gt s b usg eq (9): wc% (r eq (8)) (s prctg) = (1/G ) + (w %/100) 1+ s
(9)
wr Gs = 2,7 (pprx) ccut t xps eqs (8) d (9) r usd. T spct ts td s ustrtd b t ct tt eq (8) pps t strtg pt suc s X 1 r X2 gur 6, d t pps t stt suc s D 1 d D2 gur 6. i t pst, svr rsrcrs v sugt “t sw ”, t wtr ctts bv wc tr s
accrdg t eq (8): wc% = 0, 266 {Pi%/(lg R)}.(lg u*
– lg u* ) = 0,266 {37/lg(269)}.(lg 4 935 – lg 43,3) = 8,33%
Table 1 Comparison between measured swell (Schreiner) and Eqs (8) and (9)
SOIL
LL%
PI%
SL%
R
Measured e/(1+eo)
Calculated Equation (9)
SA-1
39%
23%
15%
113
6,0%
SA-2
47
33
8
224
20
18,4
SA-7
62
42
13
178
20
20,1
SA-13
50
37
10
269
16
17,7
ER-2
45
32
16
144
10
8,2
ER-3
49
32
16
91
15
17,7
KE-1
125
74
13
57
85
64,6
KE-2
70
43
11
80
33
30,3
KE-4
84
42
25
42
19
23,2
KE-5
39
17
23
23
1,5
2,1
KE-6
67
28
20
21
32
28,4
SU-2
69
33
10
38,4
55
54,3
7,6%
Usg eq (9) d t wtr ctt ts cs srkg t (10%), t swg prcss s btd s ws:
1+
(s prctg) =
wc% (r eq (8))
(1/Gs) + (w%/100)
=
8,33 (1/2,7 + 10/100)
= 17,7% (s sw t st cu b 1) o t cs t Scrr sps ust t xps prcss b strtd r t srkg t wtr ctt. T strtg suct u* s pprxt 700 kP r st ss Sut arc, but st cst cts t vu t strpc ctv strss suct u* prr t wttg c b s w s 120 kP.
coMMENT oN TaBlE 1 T utr ws surprsd t t tt Scrr surd prctg sw pr ut gt s s 55% r sp SU-2. T utr s vr s s wc s vrg vu r t qud t (69%), d wc s sw s rg s 55%. scd surprs ws t d tt t s d (eqs (8) d (9)) prvdd s r swr ( 54, 3%). ccuts r sp SU-2 suggstd urstc g vus suct u* t t dr s . prvt “cvtt” t wtr, t s pssb tt Scrr v usd d-rd wtr wc ctd udssvd r uc (prps t wtr ws bd d wd t c dt br us, r nd d-rtr ws usd). s bsrvt suggsts tt d-rd wtr sud b usd c dg xprts. Scrr s surd prctg sw 85% r sp Ke-1. Prps ts ws r s wr t xcssv sw s cusd b cc cg drts t gpsu-tp trs. eqs (8) d (9) w t pp t s wc xps s cusd b cc cgs.
EsTiMaTiNG iNiTial sUcTioN i prctc t d sps r usu sturtd (S r=100%). Prr t wttg, t strtg suct u* s pprxt 700 t 800 kP t dpt 1 s-rd cdts (s d surts b d Bruj (1965)). i cts suc s Cp w d Durb tt v u r wc xcds t u vprt, t strtg vu t strpc ctv strss suct u* w dpd t pst t vrg wtr tb trug t sss, d t suct u* c b s w s 120 kP t dpt 1,4 bw t s sur c. i ts cts t c w usu dsp ss cgs wtr ctt bw ts dpt 1,4 . a c wc wud b rgrdd s g xpsv ctd rd rg gt xpd sg t t uppr tr t s pr st cst rgs (s wrkd xp 2). T wtg pt pts usu ccurs t 1 500 kP. i grsss r grwg t c t t suct u* ust b ss t 1 500 kP. i rd rg stu suct u* 1 000 kP prr t wttg cud b usd r v ccuts r cprg drt cs. T skd vu t suct u* t dpt 0,5 bw t tur s surc cud b 43 t 70 kP ( tr s budg d). T tr ppr td s sutb td r surg t t suct u* prr t t wttg t c. i t
bsc suc surts t ss tt 1 000 kP sud b usd r c r s-rd rg (s xp 2 bw).
EXaMPlE 2 – coMPariNG ariD aND WETTEr rEGioNs it s usu t cpr t xps t s c rd rg d wttr rg. T cs c s t odrstprt C usd b mtjs (1992). T prtcurs rtg t t c r s ws: lqud t ll% = 89%, pst cty ndex Pi% = 57% nd Gs = 2,7. assue tt te so s octed 1,5 beow te ground. Te topso (0,5 ) w be excvted, nd concrete sb w be constructed over ts oundng dept. Te vert c od ng ro ts g t st ructu re w be 50 k P on ts so. at soe stge burst wter ppe w resut n te oodng o t e cy. Te nt wter content o te cy n te rd regon s 22%. T e nt w ter content o te cy n te wetter cte s 25%. fnd t e n percentge eve o te cy octed 1 beow te concrete sb (.e. 1,5 beow orgn ground eve). mtd ccut: eq (4) prvds t vu lg R. lg R = (Gs.Pi%)/{0,918 (ll% – 5,7)} = 2,7 x 57/(0,918 x 83,3) = 2,0126 hc t ctr R = 102,9. ) F the d egn:
(From an equivalent suction u* of 1 000 kPa to a fully soaked condition) assu tt t pr suct u t s (t dpt 1 ) prr t wttg s 1 00 0 kP. o ws t dd t xtr ctv strsss cusd b t s s -wgt t vrburd t ts v u. hwvr, s dctd rr t tr ppr td wud sur t trc suct rcvrd dsturbd sp, d t t ss tt t trc suct w st ct cpt du t prvus cts, cudg t ct t s -wgt t vrburd. i cs , t c b rgud t t t ct t s s -wgt s s cprd t t strtg vu 1 000 kP, wc ts s rug ssupt. hwvr, ust t gct t s s-wgt ct w ccutg t quvt strpc ctv strss suct u* . at t d t cstruct d wttg prcss, t vu u* s ccutd b usg eq (2) s ws: T vrtc strss ctg t s t dpt 1 bw t ccrt sb s:
vrtc strss = 50 kP + 1 x 20 = 70 kP (usg 20 kn/2 r s s-wgt bw t sb). Bcus t swg prcss t s cssr t us t pssv cfct Kp eq (2). T pssv prssur ctr s Kp = (2 + 200/70) = 4,86 (k, s ts s ss t 6).
r eq (2) w bt: u* = (0 du t u) + 70 (1 + 4,86 + 4,86)/3 = 250 kP eq (8) s usd t d t cg wtr ctt ( w%): wc% = 0, 266 {Pi%/(lg R)}.(lg u*
– lg u* ) = 0,266 {57/2,0126}.(lg 1 000 – lg 250) = 4,536%
T t wtr ctt ws 22% prr t wttg, c usg eq (9) t wg s ud:
1+
(s prctg) =
wc% (r eq (8))
(1/Gs) + (w%/100)
4,536
= 1 / 2,7 + 22/100
= 7,6% Prctg sw = 4,536/(1/2,7 + 22/100) = 7,6% Ts ust b utpd b t vrtc tckss (c) t s r t wc ts c sp rrs rdr t d t ctu v ( c) cusd b ts r. T ctrbut ( c) r c r bw t udt ust b ddd rdr t stt t v ( c) t ccrt udt. b) F the wette egn:
(From suction u* due to water table 2 m below the soil to soaked condition) Prr t cstruct, t vrtc strss t dpt 1,5 ws 1,5 x 20 = 30 kP. i w ssu tt ts s gt v drd ut sgt prr t cstruct, t t s k tt t rzt strss sud b ccutd b usg t ctv ctr K a wc w b ssud t b 0,4. assu tt rg t wtr tb s 2 bw t s surc (.. 0,5 bw t pst ts s sp). Usg eq (2), t t quvt strpc ctv strss suct u*t s
In practice the eld samples are usually saturated (Sr=100%).
u*t = (0,5 x 10) + 30 (1 + 0,4 + 0,4)/3 = 23 kP
Prior to wetting, the starting suction u* is approximately
r t xt stp, ssu tt t vu u* w st b t s s r t rd rg bv.
(see eld measurements by de Bruijn (1965)). In cities such
wc%
which exceeds the annual evaporation, the starting value
s ccutd r eq (8):
wc% = 0, 266 {Pi%/(lg R)}.(lg u*
– lg u* ) = 0,266 {57/2,0126}.(lg 23 – lg 250) = – 7,8% (.. sttt)
appg eq (9), t prctg sttt btd s 12,5%. But bcus tr pprs t b sttt, t s cssr t rccut u* b usg K = 0,4 std t Kp vu eq (2). Ts ds t u* = (0) + 70 (1 + 0,4 + 0,4)/3 = 42 kP wc% = 0, 266 {Pi%/(lg R)}.(lg u*
– lg u* ) = 0,266 {57/2,0126}.(lg 23 – lg 42) = –1,97%
700 to 800 kPa at a depth o 1 m in semi-arid conditions as Cape Town and Durban that have an annual rainall o the isotropic efective stress suction u* will depend on the position o the average water table through the seasons, and the suction u* can be as low as 120 kPa at a depth o 1,4 m below the soil surace. In these cities the clay will usually display no seasonal changes in water content below this depth o 1,4 m. A clay which would be regarded as highly expansive i located in an arid region might expand only slightly in the upper metre o the soil prole in moist coastal regions (see worked example 2)
T prctg sttt s: 1,97/(1/2,7 + 25/100) = 3,17% sttt. atrtv t c b rgud tt t vu u* s s cs t u* tt u ctv cdts v t ccurrd, d c t strpc vu K = 1,0 sud b usd eq (2). T vus r t u* = 70 kP, wc% = –3,64 % d t prctg sttt = 5,85%. T s stts. Tis foundation in the wet climate will settle due to the foundation load. It will not heave. Ts ccpt s crrct, bcus t stt t s vs up r dw t BD gur 4 s t dg d sucts r cgd ( t sgt strss ct s grd). o t quvt strpc ctv strss u* xcds t prcprss stt B gur 4 ust w pst r t BD gur 4 b csdrd.
t suct u* s wr vu w t s strts t xpd r t srkg t wtr ctt. Ts ucg stp w t b s t rwttg ccurs just br t s ws r tr. 8) lc tds wc d t d t t quvt strpc ctv strss u* prr t wttg ct b usd tr rgs. atug t V dr mrw td b st sutb r t s-rd rgs Sut arc, t s t uvrs td. 9) Dsg gudbks wrtt r s-rd cdts d t pp t wttr cts. Qutts r suc gudbks v b susd wttr rgs t cutr, d v d t ucssr substt g csts.
acKNoWlEDGEMENTs The author ackno wledges the suppor t and encouragement given by Dr
coNclUsioNs
Frank Netterberg (Pretoria), Dr Marius de Wet (University o Stellenbosch),
1) Gd grt s sw btw tr d surts b 1. T rdr c cpr t surd d prdctd vus t st tw cus b 1. T xct grt r t SU-2 d Sa-2 ss s grtg. b 1 cvrs wd vrt cs wt drt attrbrg lts. 2) w sp quts (eqs (8) d (9)) r usd t ccu t t xps. 3) nt tt t cg wtr ctt du t t cg dg (d wttg) s btd r eq (8), d tt ts qut s dpdt t vu t wtr ctt prr t wttg. 4) T wtr ctt prr t wttg pprs t dtr eq (9). 5) equt (8) t pps t xps, but s t sttts du t cprss g t BD gur (3) r gur (4) (prvdd tt t quvt ctv prssur t stt B s t xcdd). 6) T wrkd xp (n 2) cprs t sttt r xps t tw drt sts, s-rd rg d t tr wttr rg. T s c s bg csdrd, d t dg d sk g r dtc bt css. it ws sw tt t c t s-rd rg wud sw, but t wttr rg t s s wud stt. Ts s t du t cps structur t s, but s s du t t rgs t strsss d t strss-str rt (.. suct vrsus vu) t s. 7) S rsrcrs bv tt t swg c c s td t r g stur ctts, .g. ts wtr ctts wr dd b D Bruj (1961) s t wr swg t d t uppr swg t b. hwvr, t wrk ts rtc sws tt t t gr wtr ctct, s-ckg p ccurs wc s t prprt t c. as t vu u* dcrss, t r t rzt strsss b cs r prtt (s eq (2)). s rzt strss s ctrbut t t strpc strss u* wc tur rstrcts t u rtr crs t vd rt t sp. T wr swg t ccurs r t srkg t t c. Ts s s t prprt t c. it s b bsrvd b mtjs (1992) d s b xpd b Sprks (2010, prss). Ts p ccurs du t t ct tt crt suct u* ccurs t sturtd s t t t r tr (t t srkg t); but rwttg
Pro John Burland (United Kingdom) and Pro G Blight (University o the Witwatersrand). Any errors are solely attributed to the author.
aPPENDiX: Fmu the Vgn itp cndtn cuve a) The shrinkage limit (i.e. SL% water content) can be estimated as ollows: Shrinkage limit SL% = LL% – 3 x (linear shrinkage %) The author uses a linear shrinkage trough which does not have walls on opposite sides, hence the shrinkage takes place without curling o the soil sample. b) The isotropic consolidation curve ABC in Figure 4 can be described by Eqs (10) and (11) (Sparks 2010): Log (1 + LI) = 0,301 {Log (8,9 R/u*)}/{Log (8,9 R/6,3)}
(10)
or Log (u*) = Log (8,9 R) – 3,322 Log (1+LI).Log (8,9 R/6,3)
(11)
rEFErENcEs De Bruijn, C M A 1961. Swelling characteristics o a transported s oil prole at Leeuho, Vereeniging, Transvaal. Proceedings, 5th International Conerence on Soil Mechanics and Foundation Engineering, Paris, France. Dixon, H H 1909. Note on the Tensile Strength o Water, Royal Dublin Society. Meintjes, H A C 1992. Suction-load-strain relations in expansive soil. Proceedings, Conerence on Expansive Soils, Dallas, US. Schreiner, H D & Habte, K B 2008. A universal method or assessing the intrinsic expansivenes o soils. Proceedings, SAICE Conerence on Problem Soils in South Arica, Midrand. Skempton, A W & Bishop, A W 1950. The measurement o the shear strength o soils. Geotechnique, 2: 90 –108. Sparks, A D W 1999. A unied theory or clays, or students and practice. Proceedings, 12th Regional Conerence or Arica on Soil Mechanics and Geotechnical Engineering, Durban. Sparks, A D W 2010. Modelling o reconstituted clays or city planning. ICSMGE. International Conerence, Geotechnical Challenges in Megacities, Moscow, 7–10 June (in press).
Prof Eben Rust Dept of Civil Engineering University of Pretoria
[email protected] Prof Gerhard Heymann Dept of Civil Engineering University of Pretoria
[email protected] Prof Gary Jones Dept of Civil Engineering University of Pretoria Tel: 011 441 1128
Collapse potential in unsaturated soil was first identified and quantified by researchers in South Africa. A landmark paper was published by Ken Schwartz in 1985 presenting the state of the art at that time. Since then, international researchers have expanded on the understanding of what collapsible soils might entail. These include saturated silts and sensitive clays. This article highlights some of the new developments and presents a theoretical yield model in an attempt to improve the understanding of the mechanism involved iNTroDUcTioN subjct cpsb ss s t rcvd uc ttt sutr arc rct d t utrs r wr tw r t r pubcts sc t xpst b K Scwrtz 1985. s s surpr sg sc dvpt s b ts t rs cpsb ss Sut arc, t grtc ss t hgvd d t Br Rd Sds g t st cst. tr r cpsb ss, t Kr Sds, s b subjct t ss dvpt, c t c b xpctd tt ss wud v b wrtt but t. s rt c rst surss cpsb ss r trt prspctv d t cuss t tstg d dg cpsb ss r sutr arc.
Collapsible soils
n vevew collaPsiBlE soils i s cps s dd s brupt dcrs vu r wtvr rs, t t dt cpsss vst rg ss. r xp, t sstv cs Scdv d str Cd r b ts dt cpsb, dspt bg pstc d u sturtd. o t tr d, usturtd s suc s t ss rts C, Russ d str eurp cvr rus rs ts cutrs d csttut prps t cssc g cpsb ss, s d t Kr Sds. Rsdu ss suc s t hgvd grts d t brck rts Kt t UK r tr w-rcgsd grup, s, t ssr xtt, d t Br Rd Sds t sutr arc st cst. T dt b urtr xtdd, rgub, t cud t subr sd sps cst hd d t Burt S, wc v surd urs scrbd t quct; t b rgud tt quct s but stt cps. mtrs tt s t t dt r cpctd ss (Bt 1977). Rgrs (1995) suggstd t wg dt cpsb s s: “a cpsb s s wc t csttut prts v p pckg d wc rs tstb stt tt c cps t r
csr pckd, r stb structur sgct rducd vu. i st cpsb ss t structur uts w b prr r prtcs rtr t c rs. T cps prcss tt ccurs ts ss gvs t gtcc sgcc.” hwvr, Rgrs pts ut tt rtr t v dt per se, t s r usu sp t st t tpc crctrstcs cpsb s: N p structur N g vd rt N w dr dst N g prst N ggc ug r rct trd dpst N g sstvt N w trprtc bd strgt T st c rcgt tst, tr t vsu sssst, s t sg dtr cps ptt tst wc rsuts t ctgrs sw b 1 (Jgs & Kgt 1975). T rgtrs t tst, d Scwrtz (1985), pssd tt t tst ws tdd s dctr, t s t bss r td prdctg t ut cps sttt. a ubr wrkrs v ttptd t prdct cps s uct tr crctrstcs suc s dst, prst, c ctt stur ctt, sub sts, tc. i t sutr arc ctxt, Brk (1985) rprducd tw sts rtsps btw cps ptt dx d dr
dst r sds d ss xd rg, ttrbutd t Scwrtz d Pvks rspctv. Ts rtsps r rprstd b t wg quts: 1
Swell (positive strain) and collapse (negative
a sd:
strain) prediction (rom El-Sohby et al 1995) 2
Typical result rom triaxial collapse potential tests 3
CP =
– ρd 22
1672
Eect o pore fuid suction on eective stress
(cfct crrt = 0,73) (Scwrtz)
Table 1 Collapse potential test categories
Cp (%)
(1)
Severity of problem
mxd-rg ss:
0–1
No problem
1–5
Moderate trouble
5 – 10
Trouble
14 – 20
Trouble
> 20
CP =
1590– ρd
(2)
18,9
(cfct crrt = 0,77) (Pvks)
Very severe trouble
1
100
Sand - Clay Soils σ = 100KN/m Initial moisture content 8%
80
+ 5% S tr a in
+ 1 % S t ra in
i n S t r a - 1 0 %
20
0
saMPliNG aND TEsTiNG oF collaPsiBlE soils
+ 1 0 % S t ra i n
) 60 % ( t n e t n o c 40 y a l C
a i n S t r % 5 -
10
11
+ 0 % S t r a i n
a i n S t r - 1 %
12
13
14
Dry unit weight,
15 d
16
17
18
19
(kN/m)
2
0
1 ) % ( n i a r t 2 s l a i x A
3
4 0
200
400 Cell Pressure (kPa)
600
T quts p tt sds wt dr dsts grtr t 1 672 kg/ 3 d xd-rg ss wt dr dsts grtr t 1 590 kg /3 r gr t cpsb. T cfcts crrt 0,73 d 0,77 r t g, but cud pssb b prvd wt r dt. it wud, wvr, b spstc t ssu tt suc sg-uct d, rg dst, wud prvd t ptu crrt ut-uct cps ptt wt bsc s prtrs. gur 1 s tk r e-Sb t (1995). it rprsts g sw d cps prdcts bsd urus prdctv tds rprstg wrdwd bst prctc. T utrs gv tw sr d grs: r st-c d r sd-c, d t s t ttr tt s rprducd r. it cr sws tt ss wt dr dst 1 600 k g/ 3 wud t b xpctd t v cps ptts grtr t 1%.
800
hg-qut spg s rqurd r cductg cps-ptt tsts t brtr. hgt t (1992) swd tt bck spg prducs sps t gst qut cprd wt tr spg tcqus. hwvr, h & Ct (1999) ggtd dsturbcs tt ccur s rsut stur cg durg strg. ev s cgs stur ctt c cg t trc suct, d c t ctv strss, b uc r t t dg du t grg structu r. T rcdd tt sps b cvrd wt urus rs uu d purt (cg ) t prtct t gst stur cg. Rust t (2005) ptd ut s srtcgs t dtr tst r surg cps bvur. i prtcur, ts cud t bddg rrrs tt ccur du t surc rrgurts t t trc btw t s d t tp d btt prus dscs. T ccurc du t bddg rrrs bcs r prucd s t gt vr wc t sp cps s surd bcs sr, suc s t cs -ds dtr. Ts rrrs c b sgct d s css t bddg rrr c xcd t cps sttt t w sp. Sps ctg sd-szd prtcs r prtcur pr t bddg rrrs.
h (2000) d Rust t (2005) dscrbd tst r surg t cps bvur s trx pprtus. a tgr prt t tst s c str str utt wc s ttd drct t t spc w r t tp d btt prus dscs. Cductg cps tst trx pprtus ws rgr spc t b usd t t dtr but, r prtt, t us c str strutt tr xcuds rrrs du t bddg. T spc s pcd t trx t t stu stur ctt. T c prssur s crsd crts d t t rqurd c prssur, t btt drg s pd d t spc s udtd wt d-rd wtr. T rsps t c str str utt s trd s cps tks pc. T dg s subsqut ctud wd b udg cc. gur 2 sws tpc rsut cps tst cductd t trx pprtus s r t mz auu Str st mzbqu (Rust t 2005). T rsut gur 2 dcts s prtt p tt ccur durg s cps. T rst s t sudd x str 2,6% durg wttg s t pr tcs r rrrgd t dsr stt. T scd p s ss bvus, but prtt dctr r udrstdg t cs tt gvrs t cps bvur usturtd s; ts rts t t rduct vutrc stss t tr durg wttg. assug strp, t stsss br d tr wttg c b ccutd s 114 d 11 mP rspctv, dctg t-d rduct stss wttg. Rust t (2005) rgud tt ts ws du t rduct trc suct d trr rduct ctv strss. T ur tr vstgtd t cs suct d swd tt trsd stur ctt xsts wr t trx suct sudd cgs. r t mz s t bsrvd tt t suct rducs b btw 7 d 18 mP w t stur ctt gs bv t trsd. Ts dcts tt t cg ctv strss t s du t t suct prssur cgs c b ts t strss ppd t t s du t dg b grg structurs. T s sttstc cprd tw dt sts rsuts r dtr d trx cps ptt tsts tr r t s st. T ccudd tt rsuts r t trx cps
ptt tst wr uc r rb d suggstd tt ts ws du t t ct tt bddg d ct rrrs r prst t dtr tsts d r vdd t trx tst.
rg t v dt, r trws, t prpsd d. it s gr grd tt cpsb ss cprs xtur crsr s grs d tgtr b r tr wc prt trcur, ctrsttc, cpr d cc bds t dvp, tug t ts bds b prst d t rtv strgt t bd tp w dpd t s d stur ctt. r sturtd tr, ppg tt strss t t s r suct sr gtud t t pr ud s t dtc ct t ctv strss t tr. r s wt w dgr sturt, cg pr ud suct d cg tt strss t cssr
YiElD MoDEl For collaPsiNG soil Rust t (2005) dvpd ccptu d d trs ctv strss tr. Ts d d r cpsb tr s brd bsd t crtc stt d d spcc t d d r structurd ss d wk rcks s prstd b lru & Vug (1990). at ts stg t d s ccptu d ttpt ws d t qut t prtrs. it s suggstd tt utur rsrc cud b d t c3
X F
u F Y
Soil grains Water
(a)
q
u r ve
l i n e ‘
l d c
Y i e
A
B p’
‘ l i n e (b)
strgt. Cpr ts wt cg t tt strss t sp tt wud, s, rsut xct t s crs t trgrur rc. Ts cud b d t tr strss wt grs X d y cgs. o w t dstrt t csquc ts drc s sw gur 3(b). a rtv dr sp s t strpc strss a d s d surc s sw. T sp s t subjctd t crs strpc strss t pt B wr t ds. at ts pt rg vutrc strs ccur (t sp cpss) d t cpsb structur s st. Cpr ts wt t s rtv dr sp t strss pt a bg drd ut urtr. T suct prssurs crs t pt B s br, but t s skt w v tdc
v t s ct t bvur t s. T ctrbut t cpr, r suct cpt t trgrur rcs s sw gur 3(). i t s-wgt ts s s grd, t trgrur rc () btw grs X d y s uct t ud suct (u) d t r vr wc t wrks (s gur 3()). Cgg t suct btw t grs X d y cgs t trgrur rc btw t grs, but ds t cg t rsutt tr rc wt gr X r y, r r tt ttr wr s t s skt. Ts wud pp btw c pr grs wt t s ss s t bcs r usturtd, rsutg crs ctv strss d 4
Yield model
4
q
e ‘ l i n ф y ield n g
q
i
r e a
l i n e ф ‘
S h
} Swelling yield Shearing yield (a)
p’
ф ‘ li n e
K 0 A B
D C
l i n e ф ‘
q
p’
ф ‘ li n e
(c)
ф ‘ li n e
(b)
l i n e ф ‘
q
p’
K 0 A B
D
p’
ф ‘ li n e
(d) l i n e ф ‘
q
i n e K o - l
F’
F
A’
G
A G’ B
ф ‘ li n e (e)
p’
t d d t sucts cud b crsd bd pt B wt dg tkg pc. T rs r ts s tt durg drg t d surc s crsd sz bcus t crs t strgt t bds btw t grs du t suct. Ts dstrts t drc btw t cts ts tw cpts ctv strss. T suct rcs ct k bdg, wt t bd strgt bg dpdt t stur ctt r dgr sturt. Ts cud b s s suct-ducd bdg. Cpsb ss c b s s “structurd” tr udsturbd stt. Ts structur c b dstrd b xcssv str r rudg, s sw gur 4(). Tr prts t d curv b dtd: srg d, cprss d d swg d. Sr dg ccurs t vct t Φ'-s. Cprss dg ccurs btw t tw Φ'-s du t crsg ctv strss (p'). Sw dg s ccurs btw t tw Φ'-s but s du t rduct ctv strss (p'). it s pssb tt swg d ccur t gtv p' (ts) t bdg s sufct cptt, s sw gur 4(b), rtr t durg pstv p' r wk bdd tr, s sw gur 4(). T stu strss t dpt s du t vrburd prssur pus tr prssur, s w s t strpc strss cpt du t suct. i gur 4(c) t suct s rprstd b D-B d t vrburd prssur b B-a. K cdts r ssud r t vrburd prssur. Csdr t wg strss pt. Cuttg sp r usturtd pr w rv t vrburd prssur, vg t sp t pt B gur 4(c). Wttg t sp w rduc t suct, rsutg dcrs t strpc strss d vg t strss twrds pt C. Ts wttg w sutus rduc t sz t d surc du t t wkg t suct-ducd bds d t d surc w cg t t pst sw gur 4(c) s t strss pprcs pt C. at pt C t sp w d sw. Ts c b s w sp s pcd wtr d t cpt dstgrts. it s s pssb tt t sw strs w t b sufct t d t cc bds udr zr ctv strss cdts d tt dg w tk pc udr ts cdts g ts strss pt, s sw gur 4(d). i ts cs t sp w t dstgrt w pcd wtr.
a gr strss pt r t stu tr s sw gur 4(). T stu sp w b t pt a s dscussd rr. Durg wt prd t stur ctt rs bv t crtc stur ctt, rducg t suct t zr d rsutg strss rprstd b pt a’. Sc t d surc s stb stt, cps t pr w tk pc. T tstb s structur s w supprtd b t cc bdg d pssb b s rt suct prssur d rct r t vrburd strss. Pt a' s st sd t rducd d surc (gur 4()). T strss pt t -ds cps ptt tst s s sw gur 4(). it strts t t stu strss pt a. atr spg t vrburd s, curs, rvd d t strss s t pt B. T sp s pcd t dtr d dd t pt . Wtr s ddd d t suct rducd t strss stt rprstd b pst ’. at t s t, t d sur c ctrcts, rsutg dg t sp cprss t K sc ’ w 28 Civil Engineering | April 2010
s utsd t ctrctd d surc. at ts pt cps w ccur, .. rg drts w tk pc d t s w b d-structurd. T d surc t pt ’ w rprsts d-structurd cssc stt budr surc. T strss pt t trx cps ptt tst s rprstd b t strpc dg r strss pt B t pt G. T sp s t udtd, rsutg strss t pt G’ d dg cprss s wt t prvus cs, but udr strpc strss cdts.
coNclUsioNs T br trtur rvw ustrts tt, dpdg t dt cps, vr wd rg ss c udr s cdts b ptt cpsb. Ts rg c, r xp, xtd r cpctd rd pvt trs t sturtd st cs. T gr ccptd sutr arc ptt cpsb ss r t nt cst Br Rd Sds, t hgvd grtc ss d t Kr Sds. Ts b csdrd s bg t cssc r tpc rg,
vg w dsts, g vd rts d bg prt s turtd sd sts t st sds w t tt c. T trx cps ptt tst ustrts tw udt spcts tt r sst prpr udrstdg cps d tt s t s bsrvd dtr tstg. Ts r, rst, tt suct rcs dt t bvur, d scd, tt t cgs suct prssurs rsut jr cgs t stss t tr br d tr wttg. T d d dscrbd trs ctv strss d d surcs, wc tks ccut suct d tr rcs, dstrts tt t cps prcss c dd b xpd b r s ccs prcps. Bcus ts s s, t sud b xpctd tt cps bvur t d c b prdctd t s w tt csdt tstg d tr ws t prdct csdt sttt wt csdrb rbt .
NoTE The list o reerences is available rom the editor.
Charles MacRobert Graduate Civil Engineer Anglo Technical Department
[email protected] Dr Denis Kalumba Senior Lecturer Geotechnical Engineering Department of Civil Engineering University of Cape Town
[email protected] Patrick Beales Associate Geotechnical Engineer Kantey & Templer Consulting Engineers
[email protected]
Penetration testing: tet pedue nd degn ue n suth af iNTroDUcTioN Ptrt tstg s usd t g bt quttv d qutttv dscrpt t grud t b t dsg gtcc structurs. tw ptrt tsts c usd sutr arc r t stdrd ptrt tst (SP) d t dc prb supr-v (DPSh) tst. SP s crrd ut t spcc trv s wt br, w t DPSh s drv ctuus r grud v t rus. Bt tsts pp t s drv rg t prbs wt sr dtrs. hwvr, t SP rcvrs “udsturbd” s p v pdd spt sp, wrs t DPSh sp dvcs cc pt. i css t tw tsts d t prduc quvt rsuts du t drcs grud cdts, tst qupt d prt tds.
Sut arc ds t v dd stdrd r cductg d sg t tsts. Csqut, vrus trt stdrds r dptd. s stud sugt t ggt t stdrds usd d vstgt w w t r wd b gtcc prcttrs. s rtc s sws w ts prctcs c uc t rsuts btd r t SP d DPSh tsts. Scd, t rtc sks t x w t rsuts r usd gtcc dsg. a jr ssu ws t dtr wtr rsuts r t tsts r tk s quv t d wt prcuts r tk w ssug tus. dscusss ts r tc r ctrd t rsuts r su rv. hwvr, s t rspss wr td b t t vb, t s pd tt ts pubct w ctt urtr dscusss t ttr.
sPT TEsT ProcEDUrE SP surv vstgtd tr tgs: (1) wt tstg stdrd prcttrs wd w crrg ut SPs; (2) wt br dr g td ws usd; d (3) t ctu SP tstg prcdurs wd. b 1 gvs t SP stdrds usd b t gtcc prcttrs survd. Bt t aSm d BS stdrds r brd sr, but t aSm stdrd ggts s xtr prctcs. Ts cud usg gtr, strgr rds r s tk t dpt 30 . T aSm stdrd s rstrcts t dtr t br t btw 57,2 d 162 , d ws t us ctd t pu t rp ttcd t t r. atug grt drc fcc c b xpctd r ts drcs, t s b rprtd tt t us ctd c
The IRTP stipulates that when washboring, a side-discharge bit should be used to clean out the borehole and not a bottom-discharge bit. Jetting water through an open-tube sampler to clean the borehole is strongly
d t 35% vrt SP n-vu. T BS d aSm stdrds r t vst d rt, but dcts r dptts r d t t tcqu d qupt usd wt t stdrds. Ts dptts r d s rsut cpt vstt, t spcc drg tcqu usd d t grud cdts t t st. i 1988 itrt Rrc st Prcdur (iRP) ws pubsd wc ttptd t brg tgtr t drt prctcs/cds r vrus cutrs. b 2 sws t brg tst tds usd Sut arc. it s gr udrstd b gtcc prcttrs tt t spcc brg tcqu c ct t ptrt rsstc t rg xtt. T drcs rs r t brg dtr d t dgr drg dsturbc t t bs. Ct (1995) vstgtd t ct t vrus drg tds t SP n-vus prducd, d swd tt s-dtr brs, tr Table 1
SPT standards Standard
discouraged. South Arican practice or cleaning out the bottom o the hole appears to be consistent with the IRTP in this regard Table 2
ws-brd r rtr-drd, prducd csstt rsuts. Ts s t st c td usd b Sut arc prcttrs. iRP stputs tt w ws-brg, sd-dscrg bt sud b usd t c ut t br d t btt-dscrg bt. Jttg wtr trug p-tub spr t c t br s strg dscurgd. Sut arc prctc r cg ut t btt t pprs t b csstt wt t iRP ts rgrd. T prctc dsrgrdg t t 150 bw cut ssctd wt t SP tst s spc d b t iRP. Gr, survd gtcc prcttrs dsrgrd t t 150 bw cut. SP tst qu pt d td c s uc t rcrdd SP n-vu. b 3 s sur t SP td usd Sut arc cprs wt t iRP.
Practitioners’ responses
ASTM 1586-67
1
BS1377:1975 Part 9†
4
IRTP
None
†Updated to BS1377:1990 Part 9
Boring test methods Procedure
Method
Number of practitioners
Boring method
Wash-boring Rotary drilling Continuous ight auger Percussion drilling Tri-cone under slurry
5 4 1 0 1
Borehole diameter
76 mm (ID o NX core barrels)
All‡
Supporting the borehole
Casing Mud Bentonite
All† 2† 1†
Maintaining natural ground water level
Yes No
2 3
Cleaning out borehole beore doing SPT
Flush out Monitor pump pressure to minimise disturbance Side discharge tool Not done
1 1 2 1
Disregard rst 150 mm blow count
Yes Let engineer decide
4 1
Record penetration under sel-weight
Yes No
4 1
‡ Although not all noted the casing type and diameter values ranged rom 75 – 78 mm, it can be assumed that all practitioners use the NX core barrels. Whether the continuous ight auger and tri-cone under-slurry boring methods produce the same borehole diameter was not specied. † Most practitioners stated that they would use all methods depending on conditions. However, casing (without mud or bentonite) was used most oten or where required.
atr surc rrr t SP tstg td s t r wc t r s drppd. T uttc cc trp rs prduc t st sprd SP n-vus, wt rp d ctd css prducg t st. T cc trp cs s gr usd Sut arc. Rsrc Jp d t Utd Stts swd surb drc ptrt rsstc w usg rds btw 40,5 d 50 d btw a d n sz rds rspctv (Ct 1995). T dTable 3
trs rds usd Sut arc t wt t rg stputd t iRP. o gtcc prcttr rprtd usg t sd 60˚ c, wc rcts t gr trd twrds t us t spt-sp spr Sut arc.
DPsH TEsT ProcEDUrE DPSh surv xd t prcdurs wd b gtcc prcttrs Sut arc d csstd tw prts: (1) t prcdur d td
SPT Method – South Arica versus IRTP
Procedure
International Reference Test Procedure 63,5 ± 0,5 kg
63,5 kg
All
Drop height
760 mm
760 – 762 mm†
All
Driving mechanism
The release and guide mechanism shall ensure minimal resistance.
Rope and cathead Mechanical trip hammer
Control o drop height
Must ensure minimal resistance
Mechanical Visual
All –
BW 54,0 mm
2
BWY 54,1 mm
2
B 47,6 mm
2
N 60,3 mm
1
NW 66,7 mm
2
Yes
4
No
1‡
Section modulus (×10-6m3)
Rod weight (kg/m)
40,5
4,28
4,33
50
8,59
7,23
60
12,95
10,03
Rod diameter
Rods heavier than 10,03 kg/m shall not be used
Always use a splitspoon sampler
States showed no measurable dierence in penetration resistance when using rods between 40,5 and 50 mm and between A and N size rods respectively (Clayton 1995). The diameters o rods used in South Arica it within the range stipulated in the IRTP. Only one geotechnical practitioner
(“No” implies a solid 60˚ cone is sometimes used.) Standard increment over which blow count recorded
A cautionary note is given as using a solid cone can lead to higher penetration values in both loose and dense sands.
The number o blows to eect 150 mm o penetration shall be recorded, with the penetration resistance the sum o blows over 300 mm.
75 mm ͋
All
Table 4
DPSH standard Standard
Number of practitioners
˚
trend towards the use o the splitspoon sampler in South Arica
2 3
†Standard drop height is 30 inches; 2 mm dierence is due to conversion rom imperial to metric. ‡Solid cone used only when under water in ne sand and not able to retain sample with sand trap. ͋ This should not introduce error.
reported using the solid 60
cone, which relects the general
Responses
Hammer mass
Rod diameter (mm)
Research in Japan and the United
South African Practice
ASTM
1
BS ISO EN 22476-2: 2005
2
IRTP
2
Not specied
1
bg wd w cductg t s tst; d (2) t vrus tst prctcs tt gtcc prcttrs v dptd. b 4 sws t DPSh stdrds dptd b t gtcc prcttrs survd. iRP cpsss t drt stdrds d ws trr usd s bss r xg Sut arc Table 5
drp. eurp prctc s t us trdrv qupt, wt t d rp gt cc ctrd d c r r prtr uc. uc drv rt ptrt rsstc s t b xtsv vstgtd. hwvr, rsrc d xprc v dctd tt vr sw DPSh prbg c d
prctc. b 5 cprs t prcdurs stputd b t iRP wt t rspss t gtcc prcttrs survd. it s trstg (d ccrg) t t t urus tds usd b t rspdts t drv t r d t ct tt t jrt ts r vsu cu t tt t r
DPSH Method – South Arica versus IRTP Procedure
International Reference Test Procedure
South African Practice
Responses
Hammer mass
63,5 ± 0,5 kg
63,5 kg
All
Drop height
750 ± 20 mm
760–762 mm
All
Driving mechanism
The release and guide mechanism shall ensure minimal resistance. For continuously driven hammers, the hammer must be lited slowly to ensure the hammer inertia does not carry it higher than the dened height.
Mechanical winch, pulley and cable system with the drop height visually controlled
5
Continuous chain-driven with drop height mechanically controlled
1
Drive rate
Between 15 and 30 blows per minute, except in sands and gravels where it can be increased to 60 blows per minute
Varied 45 blows/minute 30 blows/minute 25 blows/minute Skill-dependent
1† 1 2 1 1
Is probing interrupted?
Probing should not be interrupted and any interruptions should be recorded
Yes No
1 5‡
Rod diameter
32 ± 0,3 mm
E size A size
Are rods checked or deormation?
The deection at the mid-point o a 1 m rod should not exceed 0,5 mm or the ve lowest push rods and 1 mm or the remainder.
Yes
6
No
–
Diameter
50,5 ± 0,5 mm
Diameter
Apex angle
90
Cone size
Apex angle
33,3 mm 41,3 mm
50 mm 60˚ 90˚
5 1
All All –
Disposable cone
Fixed or disposable cones can be used
Yes No
All –
Standard increment over which blow count recorded
Blow counts are recorded over 200 mm, with a standard range o 5–100 blows per 200 mm
100 mm 300 mm
1͋ 5
Rods rotated during probing
The rods shall be rotated one-and-a-hal turns every metre to keep the hole straight and vertical, and to reduce skin riction. When the depth exceeds 10 m, the rods shall be rotated more oten, e.g. every 0,2 m it is recommended to use a mechanised rotating device or large depths.
Yes
1#
No
5
Drilling mud used to reduce rod riction
Drilling mud is recommended as a method to re duce skin riction
Yes No
– All
Always do a re-drive to determine rod riction
Not stipulated in IRTP but suggested as good practice in the Franki Blue Book (Braatvedt et al 1995)
Yes No
3 3*
†Between 15 and 30 blows/min, except in sand where increased to 60 blows/min. ‡One respondent stated that probing is sometimes suspended during probes deeper than 15 m; another stated that any interruptions longer than 5 min are recorded. ͋ Although recorded over 100 mm, they are repor ted as blows to penetrate 300 mm by either multiplying individual blow counts per 100 mm by 3,
or adding 3 successive blow counts per 100 mm to obtain the number o blows to pe netrate 300 mm. #
One respondent stated that rods are rotated 1,5 turns every 1 m; another said that it is recommended in clays and sands.
*One respondent stated that the re-drive is only done i requested, but elt it was a waste o time. He went on to say that the bottom 1 to 2 m o a probe experiences high riction. To his knowledge, the best method or doing the re-drive is to do it ever y 5 m rom where the riction starts. Another respondent stated that re-drives are st andard on all probes deeper than 3 m and that they depend on the soil t ype.
t substt bud-up rct csv ss, wc c b strprtd s rus t prb. T iRP stputs 90˚ px g r t c. accrdg t t surv rspss, t 60˚ c s xtsv usd Sut arc. Rsrc t sp (px g) d s z (dtr) t c swd tt t dtr, d t t px g, s ct t ptrt rsstc (aggrw 1982). T dstc vr wc t bw cut s rcrdd b t rspdts s drs r t iRP stdrd. T 300 rg dptd Sut arc ws r sr crrt wt t SP (mcRbrt 2009). eurp rsrc t t crrt btw t tw tsts s spt btw usg drct crrts btw DPSh /200 d SP n/300 (Crs & mcKz 1988), d cvrtg DPSh /200 t DPSh /300 b utpg b 3/2 r xp (Crd & Rc
1
2
1988). Ts drt pprcs c s d t sudrstdgs r strprtt t grud cdts t spcc st, wc cud v svr csqucs r prtcur structur d/r gtcc prcttr. r t rspss, t pprs tt Sut arc gtcc ctrctrs d t rtt rds t rduc rct bud-up. i css, rds r rttd dvrtt w ddt rds r ddd t t strg, tug ts ds t csttut ctrd rd rtt. Rsrc b mcRbrt (2009) swd tt rd rtt sd s prs s tt ct t bw cut, v t drvg t rds s dvrtt dd r csdrb t. Rsrc b Butcr t (1995) swd tt usg drg ud c sgc t rduc rd rct c trs. n t survd rspdts usd drg ud t DPSh tst. Wrr (2007), wrtg but t crs t us t DPSh t UK, sttd t t jr ctrbutr t ts s t vbt s, vrst rgs tt c xtrct sps d d t prb tsts. Ts rsuts cst-ctv d t-fct rcvr bt sps d dst dt. Ts r st vstgt cud prv t b cstctv cprs wt t SP td, cud prvd vsu crt t grud cdts d cud cvr r t st bg vstgtd srtr t.
rEPEaTaBiliTY oF THE sPT aND DPsH TEsTs
3
4
scrt w c t tw tsts s r prcs r xct, t cg stdrd dvt t bw cuts wt dpt ws sd r spcc SP rsuts. it s ssud tt scttr du t s prprts t t spcc st r t s, trr drc sud b dctv prcdur drcs. gurs 1 d 2 ust rt dt cctd r st vstgt t mt, mzbqu. st cprsd xtsv st s d du 1 2
Matola blow counts Matola standard deviation o
blow counts with depth 3
Parow blow counts
4
Parow standard deviation o
blow counts with depth
t Br rt wc bcs prgrssv csstt wt dpt. it s cr tt t DPSh n-vus sw r r scttr t t SP n-v us. stdrd dvt t SP n-vus rs r cst t t dpt 10 , tr wc t crss std t 14 d t dcrss sgct. crs stdrd dvt c b ttrbutd t vrb gg t t st. o tw SP prbs wt dpr t 14 ; trr t sudd dcrs s du t ts td tst dt. Cvrs, t stdrd d vt s t DPSh n-vus crs grdu t dpt rug 5 , tr wc t dcrs std. s dcrs s pstutd t b t rsut t td tst dt bw 5 du t t rus bw cut bg tk s 150, rsutg wr tst rsuts dpr t 6 . at ts mt st, t SPs wr d s-dtr, rtr-drd br wt uttc trp r d t DPShs wr udrtk usg cc pu wt t drp gt
ctrd vsu. T rgr scttr DPSh rsuts c b ttrbutd t tr pr tstg tcqus r vr b bud-up rct g t DPSh rds. urtrr, s t DPSh s ctuus tst, t c b ctd b grur tr ctd wt t s pr, wc ds t grtr scttr t tst rsuts. gurs 3 d 4 ustrt dt btd b drt rspdt t st Prw, Cp w. T gg dppd crss t st, rsutg drt tcksss (rwrks), trsprtd tr (du-ds t ds, vrb st sd) d rsdu msbur tr (r, sgt c st, bcg str wt dpt). o SP ws udrtk t 1,5 d s stdrd dvt cud t b sd; wvr, bw 3 tr SP n-vus wr tk. T SP dt sw grt d r scttr t t dt r t mt st; wvr, t DPSh n-vus sw t ss scttr, xcpt btw 0,8 d 1,1 ; 2,9 d 3,0 ; d 3,7 d 4,4 . o t w, t DPSh rsuts btd prvd r r
At this Matola site, the SPTs were done in a small-diameter, rotarydrilled borehole with an automatic trip hammer and the DPSHs were undertaken using a mechanical pulley with the drop height controlled visually Civil Engineering | April 2010 35
Table 6
Rod riction consideration
Frequency
Responses
Soil type
Never
2
–
Rarely
3
Oten
–
Table 7
Any material Cohesive material Depends on the degree o clay/silt in specic soil
–
Rod riction method Method
Responses
Do not account or rod riction
2
Re-drive at reusal
1
Correlation between adjacent SPT and DPSH data
3
Empirical relationships
–
Other
1 (experience)
Table 8
UsE oF sPT aND DPsH PENETraTioN ValUEs iN DEsiGN T surv s vstgtd t us ptrt tsts gtcc dsg. T dsg spct ws sst d up ur sct s: (1) wtr grs tk rd rct t ccut w sg DPSh n-vus; (2) wtr t DPSh n d SP n-vus r tk s quv t vus; (3) w DPSh n d SP n-vus r usd tr quttv r qutttv; d (4) p qust w tr tst s prrrd. T rspss t ts scts r surs d bs 6 t 10. T sct t surv ws pprtut r t rspdts t stt t rss w t prrrd tst vr t tr. T tw rss gv r prrrg t SP wr t
DPSH and SPT correlations
Correlation
Responses
Comments
Equivalent
2
Correlate adjacent SPT and DPSH data
1
Published correlations
2
Rule o thumb
2
Table 9
prcs bw cut pr t t SP rsuts. T sudd spks t scttr DPSh n-vus r st k du t t ccs ccurrc rudd, qurtz grv d t vrb trsprtd d rsdu ss crss t st. DPSh rg usd t cct t dt usd ctuus c-drv r wt t drp gt ctrd cc. S, tug rg dgr scttr c b xpctd du t t vrb gg, t dr v cs usd r t DPSh prducs r csstt rsuts. it t rr suggsts tt ctrg t drp gt vsu s bd prctc d ds t prcs tst rsuts.
In non-plastic soil only to a maximum o 12 m depth Use site-specic data BS1377-9:1990 in situ testing (only one respondent stated source) Based on previous site investigations and visual observations o soil type
SP N = 1,2 x DPSH n (Source not given, so assumed to be a rule o thumb)
Main purposes o using data Responses Characteristic
SPT Never
Qualitative analysis: Soil characteristic boundaries, investigations o hard spots, sot spots and voids
–
Quantitative analysis: Extrapolation o actual usable parameters
–
DPSH
Rarely
Often
–
5 4
1
Never
Rarely
Often
–
1
4
–
4
1
Table 10 Quantitative use o SPT and DPSH values
Responses Characteristic
Engineering properties o soils
SPT
DPSH
Never
Rarely
Often
Never
Rarely
Often
Cohesionless soils
–
–
5
–
4
1
Cohesive soils
–
1
4
2
3
–
Cohesionless soils
1
–
4
1
4
–
Cohesive soils
1
–
4
1
4
–
Cohesionless soils
1
–
4
2
2
1
Cohesive soils
1
1
3
4
1
–
Shallow oundations Bearing capacity Piles
“udsturbd” sp rcvrd d t xtsv crrts wt dsg prtrs t t SP n-vu. extsv rsrc t t SP vr g prd gvs dsgrs r cdc ts tst. a pt rsd ws tt rb drr s sst r btg rsb dt r wc t drw p rtrs. Vub dt, suc s grdg curv d udt dctrs, c b gd r t “udsturbd” sp cctd t spt-sp spr. T sp s ws r vsu trprtt t s tp. Cst d cc wr ctd s t st ttrctv spcts t DPSh tst. a rg r c b cvrd srt prd, wg bttr dt t grud cdts vr st. w tds wr rprtd wc t tsts c b usd cjuct: rst, DPSh tsts c b usd t btw SPs d scd, DPSh tsts c dtct prb rs wc c b wd up wt br. Dtrctg r t DPSh tst ws ck xprc wt rgrd t t uc rd
rct. a cs ws g gtd b rspdt (mc Jrs, Uvrst KwZuu-nt) xpsv ur r t st rsdu cs wc t s strgts wr grss vrsttd b t DPSh. Jrs pstutd tt s t sk rct s du t tr vbrt r bwg t dr rds, wc cuss t, s ss, t j t w struck b t r. it s cr r bs 9 d 10 tt t DPSh s usd r quttv r t gt r t grud cdts, wrs t SP s usd r w ctu dsg prtrs r rqurd. rs r ts s t crrts btw gtcc dsg prtrs d SP n-vus. attpts r bg d b gtcc prcttrs t us ts crrts wt DPSh n-vus. hwvr, s b 8 sws, tr ss t b qusts but t quv c t tsts. o c tr (1) ssu tt t tsts r quv t, (2) pp quv c crrt ctr t rw
DPSh n-vus r (3) pp rct crrct (suc s r-drv) t t rsuts rw DPSh n-vus t bt quvt SP n-vus. r s s udrstdg tt t quvc t tsts s tr-spcc d tt csv trs wt sgct c/ st cpts sud b trprtd wt cut. a qut r mc Jrs bw ustrts t cudru: “i d’t bv tt tr s rb td t ccut r rd rct. crrt s cpx d r. appg ‘crrct ctr’ t DPSh vus suggsts tt suct wc s b d r t rd rct, wc t b t c s. it s t ukw r 6 r 7 rd rct st pstc c (SP ≈ 20) t cus rus t DPSh.” b 7 sws tt ccutg r rd-rct crrts wt djct SP n-vus s t st ppur td. hwvr, trs prr t r xprc. otrs just st w r dg DPSh tsts trs tt w rsut rg rct rcs d Civil Engineering | April 2010 37
tus d t v t ccut r t. o rspdt sttd tt uss r-drv t ccut r rct, but ts b rsut ck xprc g t rspdts wt t r-drv. Tr s s ck pubsd rt t ctvss t r-drv.
coNclUsioNs r t surv tstg prctcs d cprs t wt t iRP (wc cpsss t v rus trt stdrds), t s pprt tt Sut arc prctc s cpt. rr, sud Sut arc st drd b cpd wt t cprt t vrus prcttrs, prctc wud t v t cg csdrb. a Sut ar c stdrd wud p t stdrds t prctcs crss t dustr. T cprs stdrd dvts sws tt t SP rsuts btd Sut arc xbt s dgr scttr. Ts s csquc dg SPs s-dtr ws-brd brs wt cc ctrd drp cs. T DPSh c s prvd vr csstt rsuts t s udrtk wt cc ctrd drv c s t vd prtr rrrs. T cbt DPSh d wdw spg rgs cud crs t vrstt t DPSh ts tg td. T SP s usd r xtsv t t DPSh r t dsg gtcc structurs. Ts s du t t xtsv rsrc vb t SP d bcus t tst ws r sp rcvr. Cvrs, t DPSh s vurd wr cst-ctv d fct tstg td s rqurd. Dtrctrs t usg t DPSh tstg td dsg r td crrts wt dsg prtrs, ck sp rcvr d td kwdg s t t cts rd rct. as tr r ubr crrts btw t SP d dsg prtrs, t ks ss t dtr t quvc btw t tw tsts. T drv css bt t DPSh d SP r t s, but t drc cvg t rg t t prbs rsuts drt rg sss. Ts s tt t tst rsuts r t ws quvt. Tr r tw pssb ws t ccut r ts rg dscrpcs: (1) sur sss durg tstg; r (2) pp crrt ctrs tr tstg. T rg sss t DPSh
As there are a number o correlations between the SPT and design parameters, it makes sense to determine the equivalence between the two tests. The drive mechanisms in both the DPSH and SPT are the same, but the dierence in conveying the energy to the probes results in dierent energy losses c b su rd b tr dg rdrv r sur g t trqu xrtd t rds t dtr t rd rct. Crrt ctrs c b dtrd b prc cprg t rsuts r t tw tsts vrus s tps. Bt ts pprcs, wvr, rqur urtr rsrc d t s pd tt ts rtc w curg suc rsrc. Wt sufct rsrc d qupt dct, t quck d s DPSh tst td w bc v r prctc d rb.
rEFErENcEs Aggarwal, V SA 1982. Two decades o dynamic cone penetration testing in India. Proceedings, Second European Symposium on Penetration Testing, Amsterdam: Balkema, pp 215–222. Braatvedt, I H, et al 1995. A Guide to Practical Geotechnical Engineering in Southern Arica. Frankipile South Arica. Butcher, A P McElmeel, K & Powell J J 1995. Dynamic probing and its use in clay soils. In: Advances in Site Investigation Practice. London: Thomas Telord, pp 383–395. Card, G B & Roche, D P 1988. The use o continous dynamic probing in ground investigation. In: Penetration Testing in the UK . Birmingham: T homas Telord, 1988. 119-122. Cearns, P J, and McKenzie, A. “Application o dynamic cone penetrometer testing in East Anglia.” Penetration testing in the UK . Birmingham: Thomas Telord, pp 123–127. Clayton, C R 1995. The Standard Penetration Test (SPT): Methods and Use. London: CIRIA. MacRobert, C J 2009. Correlations between the Dynamic Probe Super Heavy test and the Standard Penetration Test and their application within Southern Arica. Cape Town: University o Cape Town. Warren, G 2007. Heavy weight. Ground Engng, 40(3): 36–39.
Terence Bergmann Director: Geotechnical Division HHO Africa – Cape Town
[email protected] Andrew Smith Managing Director Reinforced Earth (Pty) Ltd – Johannesburg
[email protected]
1
The use o soil nails and mechanically stabilised earth
n d embnkment tu A new road between Ugie and Langeni Sawmill, in the Eastern Cape Province, has recently been constructed by the Eastern Cape Department of Roads and Transport. The final 17 km of the road crosses the Ncembu Plateau, and descends the 600 m high Langeni escarpment. This article describes the design and construction of a 200 m length of embankment which crosses steeply sloping talus deposits. Soil nails and mechanically stabilised fill were used to form a composite structure to support the road and to stabilise the cut slope
ProJEcT DEscriPTioN Getehn nvetgtn
drt cs r t rts ssv s tru s t Burt Grup rcks. Drt tus budrs s trx vr p-jtd drt bdrck. sz, dstrbut d dpt t tus budrs r vr vrb.
wt-ur cr brs wr drd t r (Pt 2). T tus dpt vrd up t but 12 . T p jtd drt xtdd t dpts but 20 bw grud v. T budr trx s s c st. avrg drd sr strgt prtrs, bsd trx tstg udsturbd bck sps, wr
cs = 12 kP d tr rct = 35 dgrs. T budrs rd but 45% t tus vu. ar ptgrpc studs d d rcssc ud sgs cpt stbt t tus t vct t prpsd rut gt. stbty the tu pe
Stbt ss t tur sp usg t sr strgt t tus trx gv u ctr st 0,84. s suggstd tt t sp sud b swg sgs stbt , wc ws t t cs. vstgt t pct t 12 g bkt t stbt t sp, stt d t b d t strgt t trx d budr x (Pt 3). i stu tstg w s t csdrd t b rstc pt. drv t sr strgt t tus, tur sp ctr st
2
3
1
Route down the 600 m high
Langeni escarpment 2
Initial excavations into the talus slope
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Typical boulder distribution in talus slope
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Space constraints during construction
1,2 ws ssud. a bck ss gv sr strgt prtrs cs = 25 kP d tr rct = 38 dgrs. Degn ntnt
a tprr u rd d b cstructd crss t tus sp t prvd ccss t t crusr, ctd tp t scrpt. evrt ctrs rqurd t u rd t b ctd wt t r twrks prs. T xu wdt xcvt tt cud b cvd t t t t bkt wtut udrg t u rd ws 3 t 4 . a cvt cc stbsd rt w rqurd u strp gt 6 ,
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wc ws t pssb. Pt 4 ustrts t cstrd wrkg cdts. T cstruct t 12 g bkt crss t tus sp wud rsut rduct t ssud vr ctr st 1,20. Stbst surs t prv t stbt t sp wr trr rqurd. Cst cprss d durg t prr dsg stg dctd tt t us xb cc stbsd bkt (mSe) ws t st cst-ctv pt. Bt csdt d crp sttt t tus tr wr prdctd d t ws prtt tt t cs sut wud v t b b t ccdt sgct ut sttt.
DEVEloPMENT oF coMPosiTE sTrUcTUrE a cpst structur stsd t dsg crtr: 15 g s s prvd t stbt t sp d crsd t vr ctr st t bkt d t tus sp t r t 1,40. T s s prvdd stbt r t stp xcvt c bw t u rd d t us pstr strps s rt rrct, cctd t t s ds, wd t cstruct t cc stbsd rt structur cd spc (Pt 5).
prssur. T strps sud b strg ug t rsst t rzt strsss d sud b g ug t sur tt t r b t bs ts strsss rct d t pu ut t bck. T s r dsgd t rsst t ds psd t b t rrcg strps d b vr stbt rqurts. cnnetn the enng tp t the n
T strps cctg t cddg ps t t ds csst gtct, pstr brs csd prtctv pt st. T r cd btw t pts t cddg d ks t ds t s . a ut ws usd t d t k t t d d t t s t rrcg strps btw t k d t cddg. T vrtc d rzt spcgs t s wr 720 d 1 450 rspctv. T s wr pstd grd.
cntutn mn embnkment
T sut dptd ws dvpd c t cstruct d strtd. T stt t s t prcs sur vd psts ustb budr d c tus sp r g r ws csdrb cg. st t s, crwr dr rg ws rqurd d 3 wd tprr ptr d t b crtd rt t t t xcvt c. T wr s prtct ws subsqut rpcd wt tprr gut prtct. (S Pt 6.) T vrg rt stt t s vrd r but 40 t 80 pr d. a tt gt 12 0 00 s ws rqurd r t bkt. m ds wr st t r. T stt prd r t bkt std pprxt 10 ts usg, vrg, tw dr rgs. The n
Fundtn mpte tutue
Tr ws bdt t mSe structur d t ws rrw t ts bs. as drt sttt btw t d sp d t mSe bck cud ps rg ds t udt, rrcd ccrt bs wt u tckss 250 ws spcd. T wrst rw s ws cst t t udt.
inten tbty
a cc stbsd structur sud bv s crt grvt ss, dpdg t strgt d rct trct btw t rrcg strps d t bck. at c v rrcg strps, t rzt strsss t strps r dtrd b ccutg t vrtc strsss t strps d ppg t t cfct rt
soME ProBlEMs aND iNNoVaTioNs
Bkf
r-drg bck tr tt wud t dg t strps d wud s t rrgu rts t budr sp rud t ds ws rqurd. a grdd 37,5 st bck t ts rqurts d ws spcd r t tr sct wr sttc rrcg strps wr usd.
hw s-drg, grutd s wr usd, suppd 3 gts. a 72 dtr scrc dr bt ws ttcd t t rst 3 gt. addt 3 gts wr cctd durg t drg prt b s trdd cuprs. a ctrsr ws pcd t c cupr. Durg t drg prt, grut ws pupd dw t ctr w cr t . T grut ws trug t dr bt d bck up t dr . (S Pt 7.) cut pe tbtn
Durg cstruct, urus budr s d sw supg t xcvt sp ccurrd tr prgd r. T rg dsg d prvdd r gb grvt rtg w r, but t
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Polyester reinorcing straps Partially completed embankment
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Installation o soil nails into talus slope
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Completed cut slope stabilisation
ws ud t t b prctc t xcvt t bs wdt r suc w wtut jr stbt ccurrg. Tr ws s rp r ctt udrpss wc d t b ccdtd wt t cut sp. w trs cc stbsd rt, c wt ur rws s s 9 g, wr dsgd t stbs t cuttg t tus sp (Pt 8). T sst kg t pstr strp rrct t t s ds ws dptd r, s r t bkt. T ctt rp ws ccdtd btw t tw trs t w . apprxt 11 000 s s wr std ts cut sp stbst, cudg djct gutd scts. Grut tk t prb tus ws td b usg gtxt grut scks rud t s s. T dr g tcqu r drd r tt t bkt wr tp r drg d b usd. r stbst t cut sp t us dw-t- rs grt cttd t stt t s s. settement
Sttts v b trd sc t 2006, w t bkt d rcd but 50% ts gt. apprxt 120 csdt sttt d tk pc up t t d 2009. Durg t wt ss 2007/2008, w t udts t w wr sturtd r t rst t udr u d, brupt sttt up t 120 tk pc. ivstgts v ttrbutd ts t cps t p
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sttt t tus budrs. a tt 240 sttt d tk pc up t t d 2009, wt but 30 ts ccurrg sc cpt t rd pvt nvbr 2008.
wd t wdt t udt xcvt t b rducd, s tg t tgrt t u rd. it prvd t vr stbt t sd d prvdd s stbsg t uppr cut sp.
cosTs T cst ts t p bkt cstruct d sp stbst s vr g. T cst pr squr tr t cpt sst ws pprxt 8 t 10 ts tt cvt cc stbsd rt. n tr sut ws csdrd prctc, gv t prvg cstrts d ggc cdts.
coNclUsioNs T sut t t tcc, cc d vrt rqurts. it
PROJECT TEAM
cent Eastern Cape Department o Roads and Transport cnutnt HHO Arica – Camdekon JV cnutng engneeng gegt
RA Bradshaw and Associates Mn ntt LM3 JV Eth enement Reinorced Earth Company (Pty) Ltd Getehn ubntt Fairbrother Geotechnical Engineering and Franki Arica
Des Lange Technical Manager Maccaferri SA
[email protected]
Gaillard Rossouw Director PD Naidoo and Associates
[email protected]
Sinenkosi Dlamini Design Technologist & Technical Advisor DTM Systems – Maccaferri SA
[email protected]
Mike van Rooyen Director MVD Consulting Engineers (South Cape)
[email protected]
a geen utn or the design and construction o steep slopes and embankments 1
t r rtg ws d stp bkt sps. exprc gd wt ss grvt gb rtg structurs prprd t w r urtr dvpt, crprtg t prcps s rrct.
BacKGroUND
oVeR he yeaRS sc t cp bg it t t 19t ctur t sv prbs rgrdg t pct cv grg wrks t surrudg vrt, mccrr s ws usd vtv ws t trduc w d prvd tds d ssts. S t bggst cgs cd wr
T rst structur t us t rrs m (m) sst ws 14,0 g bkt Sb (ms). Ts structur ws but 1979 vr cd spc t supprt rd bkt. it csstd vrtc “sk” rck-d gb s uts tt wr crd t t structur t bkt usg rzt st strps. wg r ts xprc, t dsg ws prvd d st wr t r dub twst (D) xg s rrct sst rpcd t st strps. idpdt m uts csstd gb ut d rrct sct (t t rqurd gts) d r ctuus p D s (gurs 1 & 2). t t d t rduc vrt pct b crprtg vgtt t t rt c t structur, t ws pssb t pt cuttgs t vrtc c. T vrst tur gb cstruct d t pssb t “bttr” r stp bck t rt c, kg wc r t crprt tps t supprt t vgtt. urtr rsrc d dvpt usg t stppd-bck r spg w prcps d t t stbst t Gr
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Close-up view o GTM ace showing PVC-coated DT mesh,
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biodegradable erosion control blanket and the vegetation 2
Vertical ace Terramesh TM System showing soil reinorcement in cross-section
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Stepped-back ace to acilitate sloped prole o embankment 4
Gabion ace units replaced by vegetative topsoil to orm the Green Terramesh TM System
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A single hexagon on which the DT mesh principle is based 6 7
BioMac erosion-control blanket
Mechanical interlocking properties o the structural ll 8
Standard GTM unit showing the extended mesh “tail” that is embedded into the soil as reinorcement
rrsm rrcd ut (Gm) s “Wtr” r “S” tp (gurs 3 & 4). T Gm S tp s usd r rtg bkts d sps, w t Wtr tp, wc utss drt gsttc cpts, s usd r rvr bk prtct d t g wtr curss.
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MaTErials UsED T stdrd Gm ut cssts v gvsd 2 ,2 d 2,7 dtr st wr wc s PVC-ctd br gg trug t D prcss t r t s ps. a prvd G ctg rpcs t trdt zc td. G s cssd s zc- sst wt 5% u u d sgct xtds t t s dustr, cst d tr rs vrts. T ctd st wr s surcd r c suppr Gutg d mccrr prrs t xtrus t PVC t ts w ctr KwZuu-nt. a trs cr wt rvt SanS spccts. T PVC ctg crs wt t rqurts pprc, spcc grvt, rdss, ts strgt, duus stct, rsstc t s t spr d t xpsur t u trvt rs, brs rsstc d brttss tprtur trs ppcb aSm stdrds. ctt t prcss vgtt bdgrdb rs-ctr bkt (Bmc), d 100% ccut br, s ttcd t t sd t cd rt cg. a wdd st p d prrd trgur brckts, spd t x 45°, 60° r 70° sp g, r st bd t Bmc t supprt t cg w dg t bkt pc durg cstruct. i t S tp sst t rs-ctr bkt prtcts t tps g bd t c d prts vgttv cvr t stbs ts rpd.
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aDVaNTaGEs oF THE DT MEsH us t s xpts t r ct t surc t wr d, r prtt, t cc trckg prprts t structur . s p s du t t rg sz t pgs t s (D = 80 wt h = 100 ) rt t t dtr t w r (2,7 r 3,7 d 2, 2 d 3, 2 w ctd wt PVC). d-rsut s crs t tt strgt t rrct, wc wud b pssb r tr trs ws strgt s drvd r surc rct . ps dub-twst s sur tt t r rct s ctuus g t w gt t structu r, d t just w t t d ubr t p ts. rt d rs “wrp p” dd bck r t c t bd wt t uppr r. (S gurs 5 t 8.)
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sTrUcTUral Fill 9
Resistance to pull-out o DT steel wire mesh embedded in a 1,0 m x 1,0 m section o compacted sand at increasing normal stress 10 11
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Vertical slices analysis according to Bishop
Forces on a slice computed by Bishop’s method
T structur s t cru sctd s tr tt s usd drct bd t rrs ut d pcd d cpctd rs, w t t rrct (s r grd r cbt bt) bddd t t rs t st vrtc trvs, s spcd t dsg. Ts s ust v w s ctt d w pstct, b rtv r-drg d v r g g tr rct. it sud t ct rg srp-dgd prtcs wc cud dg t rrct durg cstruct . Cpct ust b d rs t grtr t 250 dpt d r t 95% md. aaSho.
rETaiNED BacKFill T rtd bck rs t wdg s bd t str uctur tt t Gm w s b dsgd t supprt ddt t xtr surcrg ds. Ts s ust s b w cpctd, prrb t t s dgr s t str uctur . id, ts sct w b cstructd t t s t s t structur s tt t w wrks w csst ctuus rs. Wr cssr, vrtc subs dr c b u sd t sprt ts s r t structur bck.
VEGETaTiVE ToPsoil
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s t b usd drct bd t cg p sud b tr sd c r c-k sd wt 3 t 20% rgc tr. s s sud b rt d rb d b xc vt d r 20 0 t 3 00 d pts t d. it s u d b r r wd d sts rgr t 50 x u ds. a 500 wdg t tps s pcd bd t cg d cpctd 200 ts usg gt dd cpctr. s prcss s crrd ut cjuct wt t g d cpct t djg rs structur .
VEGETaTioN ProcEss
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Wr pssb, t Gm c sud b vgttd durg cstruct r rtv s trwrds t s r prvt rs du t r d ru t c. Vgtt rqurts vr b ggrpc d ctc rgs d r trr prjct-spcc. T stpss t cg ts t ut wtr rtd b t s br ru ccurs. oc t vgtt s b stbsd t cg, t sud b prtctd. a t rrgt p d g-tr tc prgr b rqurd t sur ts survv. Ts sst ws xbt t cc vgtt, cudg rbcus vgtt (grss) ppd b drsdg r sd pugg g, r wd pts cutvtd ursr st. T sct d cc s tgr prt t vr g-tr rs ctr p d ttrctvss t sut.
rEiNForcEMENT sTrENGTH extsv rsrc s b crrd ut t prprts t 2,7 dtr D st wr s s-rrct sst. Spcs 1 wd wr usd stud t t Uvrst nw Sut Ws Cbrr, austr, d t dr hgw adstrt crrd ut u-sc tsts st t Ccg, USa. T crg cpct t srrct trc ws studd, s w s rrct rsstc. T rsuts wr usd r vrus ss, spc
t d-xts rtsp. i t dsg, prt ctrs st r ppd t sur tt t utt ts strgt t s s t xcdd udr t wrkg ds. it s s surd tt t rzt str udr d ds t d t xcssv drt.
coNsTrUcTioN oPTiMisaTioN pts cst ruct t, t Gm uts r ucturd rg szs wt vrg ut gts, t gts d t wdts.
aDDiTioNal rEiNForcEMENT
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The GTM embankment at King Shaka International Airport at
80% o the nal height, showing the initial growth o vegetation
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i stuts wr grtr rrct rsstc t t wb ts t s s rqurd, t s pssb t us tr tps rrct, suc s t mcGrd rg prc grd rrcts. Ts prduct c prvd ts strgts 60 t 200 kn/. otr trs, suc s Prlk d PrGrd, r s sutb wt strgts up t 1 00 0 kn/. i t prcss sctg trtv sst, srt “t” t s (2,0 t 3,0 g) cud b usd r t c t vrp t ddt rrct s tt t rct
rsstc t “pu-ut” s ctv, r sprt r s r grd cud b srtd btw t Gm uts t cv dqut “bd” t t rt d t rrct wr t ccts t t c t w (gur 9). T prc r gsttc grd tps csst ds rt g-strgt pstr tds csd tr durb PVC r pt stg.
TEcHNical EValUaTioN rEPorTs mccrr btd crtd rprts vutg t Gm sst r t Brts Brd agrét (BBa) Jur 2000, d t hgw ivtv cg Ctr (hieC) t USa apr 2005.
DEsiGN PriNciPlEs Stbt ss durg t dsg s crrd ut b s t qubru tr usg tr t Bsp r Jbu tds. i t prcss t rrcd s ss s dd usg rgd qubru cdts g curvr sp ps s tt cputts bsd t t d dspct c b usd t s t cts t rc sst t t trsct btw t rrct d t surc dd b t sp p. a sst r quts, wc t k t ccut t rsstg t du t t sr rcs w c pps sdg, d t vrturg t du t t dstbsg rcs, s dvpd r c sc. T ctrbut t s rrct s trducd t t ccut wr t trscts t sp p d s ssud t ct rzt. T gtud ts rcs s t wr vu t ts strgt t s d t pu -ut rsstc t s bddd t s. T rst v u s cstt d s xd b t s crctrstcs, w t scd vu vrs r wt t dpt, trs t rrct gt bd t sp surc. ec ts s rducd usg dqut prt ctrs st ccrdc wt t prtcur stdrds ppd b t dsgr. o t tts t qubru ss s t dfcut dg t str ct t grt rc t rrct, spc rspct gsttc rrcg tr. Ts crtr s b crprtd t t stwr prgr dvpd b mccrr, trug cudg up-t-dt dtbs c t p d grd rrct usd. Ts rt cuds t stc crctrstcs rqurd t d t str bvur t rrct t t pt wr t d spct s grtd, t dspct bg vrb wc dpds t gtr t surc udr ss d t cck cdts xd b t dsgr. etr u ccuts c b usd t ssss cputd dsg utputs usg ss bsd t R k r Cub ur wdg tr.
aPPlicaTioNs oF GTM iN soUTH aFrica T Gm sst s b usd r vrus ppcts Sut arc t dt, s ustrtd b t wg tw prjcts. GTM embnkment t the suth Gte: Kng shk intentn apt KZN
T bkt ws dsgd b mccrr cjuct wt PD nd d asscts. Cstruct ws c rrd ut
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One o the embankments under construction at Le Grand Gol Estate viewed rom another position on the site
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Aerial view o the GTM embankment at King Shaka International
Airport with the embankment at approximately 50% o the nal height
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udr t ib Cvs Jt Vtur b t subctrctr Cv (gurs 12 & 14). T structur cssts tw ws t rgt gs t c tr trsctg t t gst pt, wc s pprxt 12,9 (cudg 1,0 udt bdt). T tt gt s 210 d t r t Gm c s 1 520 2. T udt ws xcvtd t rd s rt d t rst 4,0 t structur cssts prtd G4 drt tr vg tr rct g 45°. T uppr 8,0 structur s t c st sd, Br Rd s, rct g 29°. T rtd bck s s t Br Rd c s ud t st. T t prps ws t cstruct t tr bkt usg t prtd drt. hwvr, rdr t cs, t trtv cbt usg Br Rd ws cs. T qutts s r s ws: drt 1 800 3; Br Rd (structur) 7 500 3; d rtd bck (Br Rd) 7 00 0 3. Cstruct ws cptd octbr 2009. bkt s b dsgd t supprt vd trrc tt uss dustr sct t t w rprt. a rd twrk trvrss ts but-up sct d v vcs r xpctd t uts t s r. a surc rg d 50 kn/ 2 ws ppd t dsg r pst 7,0 bck r t c. r r rct t wr drt bck, 110 kn/ (utt strgt) gsttc g rd ws u sd cjuct wt t stdrd s “ts” t gt 7,0 . uppr bck t Br Rd s rrcd b t s t gt 6,0 d bsd wb ts strgt 38 kn/.
i rdr t tr vt durg c struct d udr t dd cdt, sur v bcs wr ptd t vrus psts g t c bt sds. obsrvts t k t t gst sct vr prd ts r Dcbr 20 08 v dctd s vt: sttt ≈ 12 d tt-bck c ≈ 25 . Durg t s prd tr ws gr-t-vrg ss r t st d t tt rdgs vr d r + 25 t –25 , dctg tt t s bw t sur c t c b cusg csd ct t bcs. ogg bsrvts sud k ts crr. vgtt rcdd r ts ppct ws: () gr: Cynodin ; d (b) pts: Apte nia, Bul bine d Carpobrotis edulis. a ursr ws stbsd st t prpr pugs ts spcs r srt t t crrct t. hdrsdg grss tp ws s usd t s ct. le Gnd G Ette, Gege
T rst ps ts prjct ws dsgd b mVD Csutg egrs (Sut Cp) (Pt) ltd. mccrr ssstd wt dsg rvws d cstruct dts. Cstruct ws crrd ut b t ctrctr lshr Cstruct. T wrks csstd t cstruct ubr Gm bkts rgg gt r 3,0 t 14,0 stp sd sps d r t wr prts dp v tt rus trug t prprt (gur 13). T tt gt s pprxt 1 300 d t u r t c s 3 320 2. T pprxt vu structur d rtd s 47 280 3. T structur cssts grs G7 sd s wt tr g rct 30°. a gsttc rrcg grd wt 60 kn/ utt ts strgt ws usd cjuct wt t s ts. o t gst scts t w t rrct d gts 8,0 t t bs. a kkuu grs s tp, wc s vr c ts rg, ws usd t vgtt t c. irrgt t c prstd vrus cgs. i ddt t ts, t xtr dr cdts tt rg t tt t d t dfcut t urtur t r grwt t vgtt.
coNclUsioN T Gr rrsm Sst s vrst sut r t dsg stp sps tt r stb c d spcs. T cus g-strgt gsttc grd rrct ks t pssb r t sst t crr rtv g ds r t u dsg , t strs wt srvcbt rqurts. Cru ttt t t tur vgttv prcsss ks t pssb t bd t structur wt t surrudg vrt. T ctrctr sud b u cptt r cv grg wrks suc s tr sct, sttg ut d cpct ctr, d s b cpb wrkg rus wt tur t tk c r d prv t vrt, wr pssb.
acKNoWlEDGEMENTs The authors wish to thank the site sta o the Ilembe Engineering Joint Venture, especially Mr Dennis Cress, the Chie Engineer’s Representative, and AIRSERV or the aerial photograph o the GTM embankment at King Shaka Airport.
Alan Parrock Geotechnical Principal ARQ Consulting Engineers
[email protected] Michelle van den Berg Dam Engineer ARQ Consulting Engineers
[email protected] David Cameron-Ellis Dam Principal ARQ Consulting Engineers
[email protected]
Gutng – t ene?
Procedures adopted at Changuinola, Panama iNTroDUcTioN atug grutg sst b trtc dsgd d spcd durg t t stgs d prjct, sufct ttud t spccts ust b but s tt durg cstruct vrts b vkd dpdg t cdts cutrd. Ts rtc dts t t spccts r grutg sst r t udts 100 g, rr-cpctd ccrt (RCC) rc grvt d wc s t prst udr cstruct t Cgu Rvr t jug P Ctr arc (s gur 1). it s rsd tt -st cdts d ctrctu d cstruct cstrts w csstt vrts t ts spccts.
sPEciFicaTioNs Gut nteny
m grutg spccts r strc bsd t wtr:ct rt b vu,
wt t bss bg t ubr cubc t wtr t b usd wt 94 b, 1 cubc t sur ct, .. 1:1 w:c rt (bsd vu) b ccutd s 1 cubc t wtr bg quvt t (0,3048) 3 x 1 000 = 28,32 trs wtr r c 94/2,2 = 42,73 kg ct, r r cvt r stdrd 50 kg bg ct: 1:1 w:c Ξ 33 trs wtr:50 kg ct (bsd vu). Ts s bss t dr Si pprc d uc r ccptb sur s tt bsd ss. o ts ctrct tr grut csstcs wr t spcd s: 1) 66 trs wtr t 50 kg ct 1,32:1w:c bsd ss 2,0:1 bsd vu 2) 33 trs wtr t 50 kg ct 0,66:1w:c bsd ss 1,0:1 bsd vu 3) 20 trs wtr t 50 kg ct 0,40:1w:c bsd ss 0,6:1 bsd vu
hwvr, t ws ud tt ts dd t b xtdd t rg r 2:1 t 0,5:1 wt sst 1,5:1 d 1,0:1 d 0,8:1 bg usd st x tsv t t r stgs csdt grutg. r strc prspctv (rbrg tt t d ds t rts wr qutd b vu), t bv rts r dd prctc r t wg rss: ) T sts t lttj d Bruc (1977) cdt w:c > 0,45, surg stbt. b) T r sts Kutzr (1966) w ccudd tt “t st vurb w d sdtt prprts susps [ccur] wt wtr:ct rts btw 1,0 d 1,5.” c) “Rtd d studs v sw tt grut curts cstructd wt 5:1 r tr gruts td t c, wrs ts cstructd wt 3:1 r tckr r succss u.” (Wvr & Bruc 2007)
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100 m high Changuinola RCC dam under construction in Panama (Februar y 2010) 2
High-shear colloidal mixer
coNsoliDaTioN GroUTiNG o ccrt d prjcts tr s tdc t rv xcssv uts vrburd ut gd qut udt rck s rcd. s t ds t pcg t d w ccrt but t rsuts csd prts t udt bg vr uc dpr t t surruds. s grts g udsrb strss-rsr cdt wr tg dgg strss cdt ccur. i rdr t bvt ts, t s b ud t b uc r cc t tp pprxt 8 t rck ss s grutd v csdt prcdur t grt r-gus r sufct stss bw t d. at Cgu csdt grutg ws spcd 8 dp
3 4 5
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Drilling access platorm on steep slope
Graphic representation o the envisaged curtain grouting process
Developed section on the dam axis indicating envisaged oundation grouting layout
cd s t usg grut csstc 1 s dtd bv wt tckg rg grut tks ccurrd. Grutg prssur ws td t 4 vrburd (100 kP) s tt upt t udrg rck dd t ccur. a dwstg prcss ws spcd t 5 x 5 spcg wt t pckr t t surc d prbt 3 lugs. hg sr cd xrs r usd (gur 2) w t tpgrp ds t prt s ccssb psts (gur 3). W vr-rg rs t udt prr s t 5 spcg wr tt ws cssr t sur cpc wt t dsg, crt g srd r prus zs wr t cutrd wc grut tks d cctt lug vus wr g. Ts prb rs wr dtd t ppg cductd vr t tr d tprt, usu 20 x 20 bcks. ovr ts prb rs spcg ws prgrssv rducd t 2,5 r t 2d stg, 1,25 r t 3rd stgs d cssr r t 4t, 5t d 6t stgs. Sttc grutg rupturd/sr zs ws prrd d prgrssv tckg t x ws udrtk t sur tt “guprs” dd t dss ccpt grut.
cUrTaiN GroUTiNG Dwstg grutg vr gts 8, 16, 45 d 65 r tw-trds t d gt r spcd wt: N Prr s t 12 spcg N Scdr s t 6 ctrs N hs cd t 5 – 10º r vrtc twrds upstr N Pckr t surc N hs cd t 30º twrds pprprt butt N Spt spcg prcdur 5
Na
prbt tw lugs as br wt t csdt grutg, t curt grutg s w b strtd t csstc 1, d dpdg t rsuts ts b tckd t 2 d 3 cssr. Grutg w b udrtk r tw d grs d t xu grut tk s prvs b st t 100 trs/ br stg. Grutg prssurs t t dsg stg r td t pprxt dw vrburd strss t stg bg grutd. it s vsgd tt du t t cppg ct t csdt grutg w v t udt, xu prssurs 25% gr t t bv spcct w kd b prttd.
T ut d prcdurs vsgd r t curt grutg t t dsg stg r dtd gurs 4 d 5.
coNclUsioN atug spcd d dtd t drwgs, t s ccptd tt cgs t t bv dsgs w b d durg t curs t ctrct t b inter alia spdr prts d tr csdrts t b stsd. hwvr, t bsc prs csdtd udt d r-prb subsurc curt w b pursud ucprsg d wt vgur.
rEFErENcEs Kutzner, C 1966. Grouting o Rock and Soi l. Rotterdam: Balkema.
Grouting pressures at the design stage are limited to approximately midway overburden stress o the stage being grouted. It is envisaged that due to the capping eect the consolidation grouting will have on the oundation, maximum pressures 25% higher than the speciication will in all likelihood be permitted 58 Civil Engineering | April 2010
Littlejohn, G S & Bruce, D A 1977. Rock Anchors – State o the Art . Essex, UK: Foundation Publications (Previously published in Ground Engineering in ve parts, 1975–1976). Weaver, K D & Bru ce, D A 2007. Dam Foundation Grouting, revised and expanded edition. American Society o Civil Engineers (ASCE), 473 p.
Mark Laughton Geotechnical Engineer-in-Training ARQ Consulting Engineers
[email protected] Alan Parrock Geotechnical Principal ARQ Consulting Engineers
[email protected]
Identifcation o voids on the N1 North
ung gund penettng d iNTroDUcTioN Prt t Gutg rw iprvt Prjct (GiP) wrk pckg D2 cssts wdg scts t n1-21 rw. Ts rtc ds wt t sct t wstr sd t rtbud crrgw btw t attrbur d lwd Rd rps Prtr. i rdr t ccdt t wdg t rw, xcvt sps brdrg t wstr sd t rw ws rqurd.
ForMaTioN oF VoiDs wg t xcvt t sps, vds pprd vr 200 g sc t t xcvtd r. Ts vds wr pprxt 0,5 dtr d ccurrd s r tur. it, tw trs wr prpsd t xp t ccurrc ts vds. as t vds pprd prct strg t , t ws pstutd tt t v b -d d tt t wr rts d dsusd swr . T 1
Void that ormed in the excavated area
along the N1 North between the Atterbury and Lynnwood Road oramps in Pretoria
1
scd tr ws tt t vds v b brcctd rts cusd b vt rt-sut strkg ut s 1,5 k t t rt wc d b dtd ggc p.
GroUND PENETraTiNG raDar TEsTiNG
2 3
2
3
Map indicating where voids appeared along the N1 North (green line)
Equipment used or the acquisition o the data on voids along the N1 North
i rdr t scrt wtr ts vds wr r-surc r s ccu rrd t dpt, t ws dcdd tt t bst td tstg wud b b -dstructv grud ptrtg rdr (GPR). Ts td tstg c b us d t dt pssb subsurc s d s t dvtg tt t gs prducd r t ctd b t prsc trcs, djct ws r pssg trfc. Ts jb ws udrtk b eXiGe (eXprts i Gepscs). GPR s gpsc prspctg td wc c b usd t prvd g t subsurc. a t s usd t tr st ctrgtc pus wc prpgts trug t subsurc. Ts rg s rctd r budrs d bjcts t subsurc wc v ctrstg dctrc prprts. T rg s rcvd b t t d rcrdd dgt. T dpt t xprt t GPR dpds t rquc t rdr sg, .. t wr t rquc t dpr t dpt xprt, but s t pc ctv dw t s 3 . a 200 g grd ws st up vr t r wt scs bg d bt pr
d prpdcur t t rw. T pr scs wr d t 2 trvs wt t crss-scs bg d t 10 trvs g t 200 grd. S ddt scs wr crrd ut bt t t rt d sut t rg g rd t sur tt t xtt t rt t vds d b prpr dtd. i rdr t c t g-rsut g t subsurc, scs wr cductd t bt 400 d 900 mhz. T dt wr cqurd usg dstc d r t 400 mhz t d t d r t 900 mhz t t 5 trvs. a t wdw (rg) 70 d 30 scds ws usd r t 400 d 900 mhz ts rspctv. i , 78 sc s wr d wt t GSSi SiR-3000 sst, d sd usg Rd 6.5 stwr. Bsd t utput, tt 48 pssb sw vds wr dtd t dpts t xcdg 1,5 . T dt rvd s r std us zs wc wr scttrd wt t surv r, s w s cctrtd r utp us zs wt t surv r.
In order to ascertain whether these voids were only near-surface or also occurred at depth, it was decided that the best method of testing would be by non-destructive ground penetrating radar (GPR). This method of testing can be used to identify any possible subsurface anomalies and has the advantage that the images produced are not affected by the presence of trenches, adjacent walls or passing traf fic. This job was undertaken by EXIGE (EXperties In GEophysics) Wt ts rt, pprprt rcdts cud b d rd surs rqurd. it ws t pssb t dtr t d rt, but rd surs csstd xcvtg trs t dpt 1,5 d t prtg G7 qut tr 150 rs d cpctg t 93% md. aaSho dst t 0 t +2% ptu stur ctt.
udscvrd, wud kd v cusd ctstrpc dg t t w s t rw wc wud v rsutd cst rprs, s w s csurs t rct t prb. urtr tr c ds wud t v b vtb. csqucs ts, dur g t upcg 2010 ia Wrd Cup, wud v rsd s brws.
coNclUsioN
acKNoWlEDGEMENTs
rsuts prvdd b t GPR tstg bd t xtt t vds t t rd t b dtd. s vds,
The permission o SANRAL, the BRCD joint venture and EXIGE to publish this article is acknowledged with thanks.
Civil Engineering | April 2010 61
Louis du Plessis Geotechnical Engineer-in-Training ARQ Consulting Engineers
[email protected] Alan Parrock Geotechnical Principal ARQ Consulting Engineers
[email protected]
Lateral support or Get Wetefd extenn iNTroDUcTioN i 2006, ps r xtss t t xstg Grt Wstrrd cpx Rdbsc, Cp w, wr pprvd b t ct, attrbur Cp. T xtss t ts budg cud tr-v bst r
1
prkg, wc t ts dpst pt w b s 10 t 12 dp. Prr dsg dctd tt t cc w cductg ts xcvt ws v cbt bttrd sps d csd tr supprt. Ts rtc dts t prcss.
siTE iNVEsTiGaTioNs w st vstgts d prvus b cductd: r t structur 1985 d tr r t xtss 2006. Bt vstgts utsd cr drg t dpts rgg r 17 t 30 . Ggc, t Grt Wstrrd cpx s udr b dp wtrd t-sdtr strt t grbrg rt, msbur Grup, wt vrb cvr trsprtd (uv d/r cuvus) d rsdu ss. r t rtr-cr drg vstgts cductd, t wg grsd subsurc pr ws ud t b prtt r t stud r: N Tnpted mte: Cprss du-ds st d c sd wt s budrs (xu 250 dtr). Ts r ws cutrd t pprxt 12,5 . N redu mte: St t vr st c st. Jtg ws vdt wt t rsdu s ss. N Bedk: hg wtrd vr st t drt wtrd st rck, 1
Test pit excavated to -5,5 m on the
western boundary o the Great Westerord complex in Rondebosch, Cape Town
2
Making good progress with the excavations. Notice the large tree on the northern ace 3
View o the north-western slope
msbur s. bdrck v ws ud t b g vr b, wt dpts rgg r 18 t 28 . T wtr tb v ws ud t stbs t but 8 t 9 dp. rcdt r t st vstgts ws t bttr t sps t 33˚ bv t wtr tb w t trckg st ps (t ctr t grudwtr spg) r t dpr vs.
2
sEcoND oPiNioN aRQ Csutg egrs ws pprcd b Dkkr d Gdrb, t structur grs, m 2009 r trtv supprt surs s t rg rcdt ws prvg t cst r t vb budgt. aRQ rqustd t ctrctr t xcvt tst pt t –5,5 djct t t wstr budr t st, utsg xc vtr. T pu rps t s ts t pt ws t vsu vut t subsurc gtr r stb t, s w s t bckccut t k durg-cstruct sr strgt prtrs r prr dsg. r t tr bsrvd, t prtrs wr sttd s: c = 31 kP φ = 26˚ γ = 18 kn/³
3
T cs prtr ws dwscd t c = 25 kP t grt dcu csrvts.
EValUaTioN Sp gs (t oS 1,3) wr dtrd s 50˚ d 57˚ r t dpts xcvt vsgd. Durg xcvt, tw ptt prbtc rs wr dtd: t rg tr t rtr dg t xcvt d grg t wstr dg. at t tr, t sp ws stbsd b st g tr rws 9, 6 d 4 g s r r 3 t tr sd t tr t uppr vs d 4,5 t wr. Trdbr 500 y20 s wr spcd, but du t t ctrctr vg y25s stck, t ws dcdd t us t ttr std. at t grg t sut-wstr crr t st, t 8 g sp t 50˚ ws ud t v u oS 1,47 wt 10 kP surcrg
t sut t grg. atug t rst gc t s pprd ccptb, w t ss ws rptd prbbstc d, t prbbt ur (oS ≤ 1,0) ws ssssd s 8%. wg t rcdts s pr b 2 Krst (1983), ts v rbt wud grt: N srt-tr srvcb N prvt pubc ccss N t d r ctuus trg N t dd ustb prt sp. Trr, tug t sp t ts sct ws prdctd t b stb t srt tr, t ws rcdd tt trg pgs b std t t tp t sp t 5 trvs.
laBoraTorY TEsTiNG as t prr dsg ws bsd st ts (bt rsd s), udsturbd sp ws tk st r tstg. i ttpt t d t ctu cdts tt wud b prst st durg t cst ruct prcss, t sp ws tstd tr st (wc wud sut t
udrd cdt) r sw (wc wud sut t g-tr drd cdt). i ddt t t s, t wtr ctt ws td t t stu vu s t w s rsd tt t st w ts t r, t Cp ws gg t t drr ts sur. rsuts r t trx tst wr sd r t prbc strss-str prtrs s pr Duc t (1980). Rprsttv sr strgt vus r t tr st udr t cdts k t b prvt durg cstruct bst b rprstd b:
s < 5 , xcpt r cs 9 . it wud tus ppr tt grg judgt, supptd wt xprc, d t cs t-ctv sut wtut udu xps.
acKNoWlEDGEMENTs Permission o Atterbury Cape, and Dekker and Gelderblom to publish this paper is acknowledged with thanks.
rEFErENcEs Duncan J M, Byrne P, Wong K S and Mabry P 1980. Strength, stress strain, and bulk modulus parameters or inite element analyses o stresses and movements in
Nc
= 30 kP N φ = 28˚ N γ = 18,6 k n/³
soil masses. Report No UCB/GT/80 01 o the Charles E. Via, Jr. Department o Civil Engineering, Virginia Polythechnic Institute and State University. 70 pp
r ts t ws pprt tt t prtrs usd t prr vut wr vr cs t ts tstd.
plus Appendix detailing FORTRAN computer print-out listing. Kirsten H A D 1983. Signiicance o the probability o ailure in slope engi-
coNclUsioN
neering. The Civil Engineer in South
T bv surs wr ptd d t dt t trg pg vt
Arica, 25 (1): 17–27 and subsequent discussion 25 (6): 317–332
Civil Engineering | April 2010 65
Marie Basson Geotechnical Engineer-in-Training ARQ Consulting Engineers
[email protected]
4
Alan Parrock Geotechnical Principal ARQ Consulting Engineers
[email protected]
1
2
5
3
6
Eden ind
Paradise Engineered HisTorY S 180 rs g, w t ct supr-ctt Pg crubd, grup gct brk-w ss bg t drt sw crss t c prv c, 1 60 0 k r wt s, td, t st cst a rc. it s ts prt t g rtc mscr Ptu wc brk r t id Pt but 65 rs g ckc sprkg sd jws strug wt vsb trds svr sur tt k up t Scs. Suc ws tr st tt t ursd r , r r t tur tr dstt wrds, vstd b r arb vgtrs w gv t ptc s ur tr rt-stppg tur but. d t st but u sd rcpgs t wrd, d t cc sds grtc rck, s br v urs g t r Jsburg. Surrudd b dc dstts t st cst arc, just rt-st t sds mdgscr d Crs, st Zzbr d rt murtus, t tru s t rt prds.
uxur prtts udd rts, ps d cbt t rts d pd udts.
GEoloGY T Scs s prt t r t rt ssctd wt Réu d t Dcc trps id. T grtc r s ds r t wrd’s dst, w t utr s r vr ug, rsd cr sds tt v rgd d subrgd svr ts durg tr g str, t st rct subrgc dtg bck t 125 000 rs g. i r r trs, t rcpg ws crtd s rs g b cbt t sprt id r arc, s w s udrs vcs sr t ts r wc murtus d Réu wr crtd. Subsqut, t vst jrt ts ug d r bc subrgd vr t.
cliMaTE T ct t Scs s csstt stb. Vrg b cup dgrs, t wtr s ws grus trpc, rgg btw 24 t 31°C r rud.
THE DaWN oF EDEN islaND ccpt “w prds” tk sp wt t d dsgg, spg d udg 450 rd-tt 1
CAT 325B busies itsel with basin
excavation on Eden Island in the Seychelles 2
Private marinas on piled oundations
are typical o the surroundings 3
Structures such as the jetties, and
this bridge connecting Eden Island to Mahé, are ounded on capped piles 4
Engineering site in paradise
5
Drop weight system employed at Eden Island
6
Gauges installed on CAPWAP test pile
iNVolVEMENT aND GENEral ENGiNEEriNG coNDiTioNs i august 2007 id oc Prjct mgrs hs Djkstr d hrrs Ct pprcd a Prrck, gtcc prcp Sut arcbsd csutg r aRQ, r put sp stbt ssu st t Scs. Cstruct t s d cudd drdgg t cr, cr sds, st cs d r sdt bv cr r, t crt ptr s 3,5 bv aCD (adrt Crt Dtu).
7
(aCD = gr –1,05 s v wt s csd gr rs.) T cr r vrs v r –0, 5 aCD t –3 aCD, wt r gg csstg vrb cr rts d r sdts vrg crs d du-grd grt t pprxt dpt –30 aCD. o t k ssus ws t stbt d cstructbt rs wr pstc sturtd st cs prdtd. r s wr xcvtd t bss, d pr gggs, grdgs, CBRs, dsts d sr strgt prtrs wr dtrd. Stdrd ptrt tsts r 13 crs cductd st rvd gr trd ds uppr r (0–3 ), s r r 3 t 15 d grdu stg wt dpt r 15 t 30 . ass t dt crd tt t tr s st csss d tt t uv sttgs wc ed isd s stutd wud grt t bst gt vrcsdtd dpsts.
DYNaMic PilE TEsTiNG
8
Dc p tstg usg t CaPWaP td ws prrd rdr t prdct cpct d vt ccurt. rr cgu rvr Gr cductd t tstg s t ps. Sttstc ss t rsuts dctd tt t 300 dtr ps std t prdt 10 wud, t t 97% cdc v, b gd r srvcbt cpct 200 kn. Rck-s rts wr usd udr sr structurs cjuct wt g-strgt gsttcs t t bs. Ktc’s Rckgrd PC 50/50 ws spcd t sur tt pstc tr cud tr t rck d dstr trprtc sr.
coNclUsioN T Scs rs sub tur but, st d trqu t. n ttr wt brc grg v cs, wrkg suc prjct suc cptvtg vrt s xprc vr cv gr drs but.
acKNoWlEDGEMENT Permission to publish this article is acknowledged with thanks to all those involved. 7
Close up o gauges installed
on CAPWAP test pile 8
Graphical ormat o SPT data or
13 coreholes conducted on site
Eulane Heukelman ARQ Consulting Engineers
[email protected] Hennie Barnard Aurecon SA
[email protected]
Building the uture with the Geotechnical Division o SAICE
– ht ue n pbem he GeoeChniCal DiViSion SaiCe d srt curs Prb Ss august 2 009. Ts curs ws r-ru t 1985 Prb Ss Curs cusg spc studts, ug grs d ug gr g ggsts. T tt ws t k ts curs s rdb s pssb d t ws dcdd t crg ut r wrkg grs d grg ggsts; r studts t ws cpt r crg. Ts ws pssb du t t supprt urus spsrs, t w w r vr grtu. T vrus prb ss wr dscussd d prstd b s ur tp gtcc grs d grg ggsts w rd tr t d rt r crg t prst tr w-vd tpcs: Dr rtz Wgr (dts), mr Ptr D (vg cs), mr K Scwrtz (cpsb ss), Dr P Pg-Gr (dsprsv ss) d Dr Gr Js (st cs). T srt curs ws d tr cts, .. Durb (6 august) t t Uvrst KwZuu-nt, Prtr (13 august) t t Uvrst Prtr, d Cp w (21 august) t t Brkwtr ldg (Uvrst Cp w’s Grdut Sc Busss). T vt cprsd u d v ssss t vrus prb ss. T curs ws vr w ttdd b tt but 640 dgts d xct dbck ws rcvd r t uvrsts d ttds. T curs ws rgsd b tw t ctt’s ugr brs, h Brrd (aurc Sa) d eu huk (aRQ Csutg egrs) wt t p t prvus cr (Dr SW Jcbsz), t prvus scrtr (Dr edurd Vrstr), t trsurr (htr Dvs) d rvr Gr. T Gtcc Dvs SaiCe wud k t tk t wg cps scr r tr spsrsp: esrrk mccrr Sa Gutg Pg Ktc aurc Sa Gsur V VKe
DURa GCD Rrcd ert aRQ Js & Wgr Pqup
1
2
naUe Gel Stutt Stcks BKS Kgt Psd 1
, t Dvs wud k t xprss ts scr grttud t t v spkrs w rd tr xprt xprc t t bt ug grs d studts.
At the University o Pretoria approximately 300 engineers and
engineering geologists attended the problem soils course 2
The ve presenters, rom let: Peter Day, Ken Schwartz, Dr
Phil Paige-Green, Dr Fritz Wagener and Dr Gary Jones
Eulane Heukelman ARQ Consulting Engineers
[email protected] Alan Parrock Geotechnical Principal ARQ Consulting Engineers
[email protected]
if yu wh t eh the tp, tt t the bttm
A young engineer’s thoughts on geotechnical engineering iNTroDUcTioN evr xprcd, spcst gr c, g t g, strtd t t btt t ddr. r ug grs tr s pt tt s t b wd t gt t gr grud. Ts srt rtc w, wt t cus gtcc grg, ttpt t xp k tgs tt d t b prt t stppg sts t t bgg grg crr. rc t tp ut s t strt t t btt. Ts sud vr sp, but t w bgs t d grg tr cptg dgr, t tkg s: “i kw vrtg d i gg t k ts cp bttr.” pts r pstv tkg, but urtut dgr just prvds t tckt t brd t gt, t cc t t p!
THE sTEPPiNG sToNEs i coNsiDEr iMPorTaNT T wg pts r prtt t t strt crr gtcc grg: 1. Rs tt u r gg t k stks, dt t d r r t. 2. r t b vvd t prts prjct, r tdrg, budgtg, pg d dsgg trug t xcutg. 3. D ur w gtcc vstgt. it s vr prtt t gt r wc ss d rcks udr st. lk r sgs – crcks budgs, sttt udts, d t wt gs t surrudg sps ccur tur. aws b s wr s pssb.
4. it s vr prtt t ctu ur duct – SaiCe’s Gtcc Dvs d t uvrsts v curss tt u c ttd. s curss w crt wrss spcsd ds d supp usu rt tt c b ppd t ccu ts, dwrk d dsg suts. 5. B prt t Gtcc Dvs – t s wdru t t pp t dustr tg tt s t cssr wrk-rtd. 6. hvg tr s prbb t st prtt stppg st. hv t tks crr drct d wt st ds t b d t rgstr s prss gr. 7. St xprc s vr prtt. yu sud v t st 10 ts st xprc. o st t s gd t r w drt ctrctrs wrk. T tg s t cg tk g prcsss t prduc bttr, r cst-ctv, s d gr dsgs. 8. r t b xpsd t t ds gtcc grg br dcdg wt t spcs , bcus ts ds r tr-rtd.
coNclUsioN i p ts w spr ug grs d prvd s gudc r t utu r. i pg tr w c crt bttr vrt wc t r d t rc gs str. it s vr gd tg prc tc t sts z ut tt d k t t bggr pctur.
MARKET CONTRIBUTION
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f d pvement 1
Promising results from one of the latest innovative cement additives provisionally certified by Agrément South Africa as fit for purpose BacKGroUND
2
Rd cstruct s but prducg d stbsg structur tt w ctv srvc t rt-bud cuct ds t cut. Srvc dvr d prjct-dcs ctrg ccpts suc s bt, ccssbt, cc, srvc v, cc strtg d cst, rd rstructu r sustbt , tc, br wtss t t prtc ts . hc grtr cc tr rsurc utst d cstructbt s cssr d prtt r ts cpts t c-trg udrpgs cutr. s r tc ustrts w s ts prcps wr ppd t rd rbtt prjct t nrt Wst Prvc Sut arc. rd qust s Prvc Rut R52, jr prvc rut rug btw t tws Kstr d lctburg. a 40 k sct t 86 k tt rut gt (ps 1) s udr cstruct s t wrtg ts rtc. atug t rut s b srvc r ubr
dcds, t prst pvt s b srvc r but 20 rs d ws swg sgs dstrss . it dd structur d uct rbtt d upgrdg, spc wg t t ubr v vcs wt ts tr c spctru wc dstrbut c prduc d s prducts suc s d ct. Rr t gur 1 r t r p d gur 2 r gr v w t rd prr t rbtt. prvc utrt d tr csu tt dcdd t pt r t vtv d vrt rd s ut dscrbd bw, rtr t t r trdt pvt cpst, d s t ppct dd cts stbs g prcss. s td ddg RdC t t ct-stbsg gt, prduct t cp PwrC cgs bsd t ntrds. it s t tst vtv ct ddtvs prvs crtd b agrét Sut arc s t r purps (pdg t utc t tw-r g-tr ppct trg prd). ctrct, wc strtd nvbr 2008, ws t b t Dprtt rsprt, Rds d Cut S t t nrt Wst Prvc Gvrt t t tdr prc R205 vr prd 12 ts.
1
Location o Route R52 between Koster and Lichtenburg
2
General view o the road prior to rehabilitation
3
Typical chert gravel o the area
4
Map o Route R52 area showing the location o the dierent construction sections
5
Example o DCP inormation available
3
4
aiMs aND oBJEcTiVEs Sc Rut R52 s t d tr sprt rtrs btw t PWV r ( prtcu r t Prtr/sw r d mpug) d mkg, t s t t g st drd srvcbt t s rut. Rct, tug t rd d b prr g w, t utrts td crsg sgs pvt dstrss, s w s ccrt t rdw/sudr drp- wr rt du t t crs tr c, spc v vcs (t prst u vrg d trc (aa D) s t vct 1 972 wt 15% v vcs). it ws t t prv t srvc v t rut d s gv t pvt w s . uct t tr c stut cd r crs rdw wdt r t xstg 7,8 t 10,4 crt strtcs t rut d structur cpct eS8 rptts (3–10 m Stdrd ax s, miSa), wrs t rg pvt d b but t eS6 brg cpct stdrd (Colo, 1996). structur stut t b rsvd ws w t crs t b rg cpct t pvt substt w utsg t stu tr pt rdr t s t d r ddt tr/ brrw pts.
ProJEcT DEscriPTioN aND DEsiGN prjct bsc cssts wdg d structur rbttg t xstg rd, wc trvrss t rtv t, g t rg trr t rsv Suprgrup wc cts ggrgts d ss dtc rg d ecc s t ttud rgg btw 1 50 0 d 1 600 bv s v. Rr t gur 3 r xp t c grv. l ndtn
rtut t qut t uppr 600 t stu crt grv ws rtv gd, vg vrg brtr
Koster
2/1 3/2
4/3 5/4 6/5
Lichtenburg
Number of Blows
0
50
25
50
75
100
125
150
) 150 s e 300 r t e m 450 i l l i M 600 ( h 750 t p e D 900
1050
Estimated CBR (%)
2
0
3
5
7
10
15
20
30
40
60
100
1 40
200
150
) s 300 e r t e 450 m i l l i
600
M ( h 750 t p e 900 D
1050 Actual
Required At The Depth For 3 MESA
Layer Property Summary (For Reference Depth of 0 Millimetres) Thickness (Millimetres)
Avg. Penetration Rate (Millimetres/Blow)
Estimated CBR (%)
Estimated Stiffness (MPa)
150 150 150 150
7,25 7.25 9.1 9,1 4.5 4,5 5.33 5,33
33 67 61 40
59,7- (135) - 311 147- (335) - 765 99,1- (225) - 515 82,7- (189) - 430
Total Penetration Summary Est Pavement Capacity Based on DSN900 2,9 MESA if Dry 1,4 MESA if at Optimum Moisture 0,6 MESA if Wet 0,3 MESA if Saturated
General Notes Blows to penetrate 800 mm - 154 Penetration Rate to CBR conversion is based on the relationship published by Kleyn (60 Deg. Cone)
Road P34/2, DCP Results in Wheelpaths km 72
CBR vu 65% t 100% md. aaSho, Pi 5, Gm 1,8 d r sr kg vu but 3%. pssbt r-usg t stu tr t rbtt dsg trr prstd ts v t tt stg. iprtd c crt grv wud t b dd t cpst r v crrcts d wdg t rdw wr cssr. s pd t dr t t pssbt r vtv d vrt rd pvt rbtt dsg. Rrrg t t p gur 4, t prjct ws dvdd t vrus scts s dctd bw, bsd vsu cdt sssst d D c C Ptrtr (DCP) ss (K 1975; K & Svg 1982). gur 5 sws xp t DCP rt sts vb r t rd t 1 k trvs. N Sct 1: Kstr t 10 k – r rcstr uct N Sct 2: 10 k t 33 k – xt ps prjct N Sct 3: 33 k t 42 k – rcstruct wt RdC ddtv bs N Sct 4: 42 k t 65 k – su rcg rbtt pus wdg pvt N Sct 5: 65 k t 83 k – rb wt RdC ddtv bs N Sct 6: 83 k t lctburg – r rcstruct Sct 5 w b usd s xp r dscuss ts rtc. DCP surts g t rd swd t stu pvt strgt t b qu curgg, s dctd gur 6. nt tt t vrg bscurs strgt w s bw tt t brtr vu d s rtv w wt rspct t t stu strgt rg – spc w sr cprd t t subrs. s ws prbb rg du t rtv g stur ctt t g bs s rsut t prus d dstrssd surcg. yt, , t stu tr cdts wud dd w r vtv cvrs t xst g pvt t eS8 brg cpct qut (Colo 1996) b rwrkg d rstbsg t tp prt (bs d subbs) t pvt. hwvr, w t s ws tc c pssb, t prpst r ct stbsd grv t crck s vr, w wtr t t pvt d tt t pvt ur c c (spc wt d rt s tc), s w kw d g-stdg ccr tr/pvt dsg grs d tccs. 6
Average pavement strengths or section 5 o Route 52
The pvement ehbttn degn
In situ CBR % 6
0
20
40
60
80 100 120 140 160 180 200 220 240 260 280 300
0 C3 Design basecourse strength
100
As-built strength
200
300
C4 Design subbase strength
Depth mm 400
500
Average 100% Mod AASHTO CBR
DCP measrued in situ strength range of existing pavement
600 Average in situ strength
700
DCP measured as-built strength range at this depth
it ws t ts s tg t rbtt dsg tt t xstc RdC ws brugt t t ttt t ct, t csutt d t ctrctr. prduct s pwdrd r pttd bd zts, sctd k s, k r t ts, tc, wc w ddd t ct-s xtur s qutts (1 kg/ 3 s r 0,05% b wgt) ssst bdg trs t strg rgc cpud. prcss rpd prducs dk cttus crst trx wt t ct-s wc xtds crss t trprtc vds d sssts cpsutg d trwvg t s prtcs t wt b trd “s brc”. it s r ss pr t t t pc crckg ct stbst, prts rpd strgt g d s ss brtt t t trdt, r rgd cc “gug” s prtcs.
urtrr, d vr prtt r rd budg purpss, t prcss r-rgg stur s dspd r t s trx, tus crsg t c tv dst d t stur prvusss t bdd tr wtut ddt cpct rt. prduct s vb s ptsd prprtr bd (pwdr) r c b bdd t sut st-spcc cdts d ctt vs (mrjvc t . 20 09). it sd tt ts ddtv wud rsv st t ccrs rgrdg t dg r-usb t swt vrb tr sufct w t d vr t dvtgs td bw, d tus wrrt vstgtr ppct. it ws ccudd tt t wg bts wud ccru r t us ts ddtv: N it wud b pssb t crs t strgt d prrc t stu g rv suct b u sg RdCbstd ct stbst t rpc t crusd st bs trdt rcdd r ts pvt brg cpct v. N vr w vd ctt t ctd s trx rsutg r t trwvg crst ttc wrk prcss t ddtv wud crs t ctv dst wtut dg ddt cpct rg. N hg stur prbt du t t crs ctv dst t r wud rsut dcrsd stur suscptbt t bscurs – spc t c drt s tc.
N Substt
ss ct stbs t crckg wud ss stur grss, ss ptt ss br g cpct d ss subsqut pvt ur. N Rpd bud-up brg cpct c t trtd grv d b cpctd d t s bdg, pr tc-trwvg prcss t ddtv d tk ct. N r wud b svg cstruct t bcus t vsd vtv pvt cpst, vdg rcstruct t tr pvt, spc wt vrt scrrg prtd tr. W t b ccudd r t trtur tt ts ddtv cgs t prprts bdd trs t w tu g t ct dsg rt s w s t us rtv “rg” trs wt g rtr cdc, ts spcts wr t spcc vstgtd udr ts ctrct. T cpst t rg, d r trdt, rbtt dsg r ts tp brg cpct ccrdg t Colo (1996) ws t dd s ws (s rr t gur 6): N Bs – 20 0 tck rwrkd ct/RdC stbsd t stdrds C3 (1,5–3,0 mP UCS) std t r trdt 150 G1/G2. (Dpdg t p d v crrcts ts cud vr btw u prtd d u stu tr.) N Subbs – 150 tck rwrkd ct stbsd t C4 stdrds (0,75–1,5 mP UCS) std t trdt 250 C3 r. (Dpdg t pd Civil Engineering | April 2010 75
7
Windrowing top 350 mm o existing pavement 8
9
Early morning RoadCem spreading operation
Cement application (on top o the RoadCem) and dosage rate control 10
Completed hal-width cement spread on top o applied RoadCem 11
Stabiliser and additive being mixed into basecourse material (drum tiller plus coupled water tanker train)
12 13
v crrcts ts r cud vr bt w bg t rwrkd d stb sd stu bs curs r subbs.) N Sctd rs – rt t stu structur gr swg G7, G9 d G10 qu ts rspc tv, d t rr st c wr t d t, s cpct s d br brgg bck t subbs. N Surcg – ws cgd t 19/9,5 dub s r t suggstd 40 spt, wc w s csdrd t b r sutb r t prvg rur cdts, wtut t cst pru. r gur 6 t c b s tt ts dsg utss t stu pvt strgt w, swt csrvtv trs bs tckss , rsutg rtv dp d vrdtrt pvt. s t t tt t bs wud b stbsd wt 3% ct (b wgt) pus 1 kg/ 3 (but 0,05% b wgt) RdC ddtv, d t subbs wt but 2,5% ct. s dsg ws usd wr t pvt d t b wdd – tr ddt crt grv ws prtd r c brrw pt t brg t bs r surc t v. it ws s dcdd t rbtt scts pvt wt ddtv s ctr r cprs. s s cts wud trws rcv t s ct dsg d trtt s t scts trtd wt ddtv.
A smooth, hard and crack-ree basecourse surace Close-up o basecourse where additive was used 14
Close-up o control basecourse where no additive was used – note cracking
coNsTrUcTioN ProcEss Sc vr w d s gt grdg crrcts d t b d, t pvt rbtt cstruct cgs c b
7
8
11
12
dscrbd bsd Sct 5 t p sw gur 4 s tpc xp. step 1: vs wr st ut d suct tckss, dpdg t v crrct rqurd t tt pt t ccdt t bs d subbs (up t 350 ), t xstg pvt ws w drwd (s gur 7). step 2: xpsd tr ws cpctd s cssr t u 90% md. aaSho t srv s t sctd r. step 3: Subbs tr ws prtd r t wdrw (d t brrw pt s rqurd) d sprd t v r 150 tck cpctd r d tpd dw t c tt sprdg t ct stbs r. step 4: ct stbsr ws dstrbutd t spcct b d (ct pckts), sprd d xd b grdr r s-prpd t r d cpctd t 150 tckss t u dst 95% md. aaSho. (Dst qut ctr ts prjct ws d b ucr rdt str ut.) DCP surts d t subbs t tr stg dctd stu quvt CBR strgt t st 160%, s sw gur 6. step 5: Bscurs tr ws prtd r t wdrw (d brrw pt s rqurd), w g r v crrcts s cssr , d tpd dw t ctt cc dstrbut t stbs r d ddtv. step 6: ct d ddtv wr sprd t spcct. ddtv ws rst ppd b d (s gur 8) d
t t ct (dsg rt ctrd) s sw gurs 9 d 10. sprd rt qut w s ud t b crtb wt spc ct ts prjct. wsd t prpsd td sprdg t ddtv ws t qustd b t ctrctr s rgrds t t k d ccurc. hwvr, t ws ud tt t 12 burrs cud cvr 900 t 950 2 1 t 1,5 urs wt su ct ccurc t rsut r t dqut qut ctr rsuts – 1,8 mP t 3,4 mP UCS wt 2, 3 mP vrg rcrdd (s gur 6). (as sttd b t ucturr, dscrt r cts wr tcd r dg t ddtv.) step 7: stbsr wt t ddtv ws xd b s-prpd dru tr ccpd b cupd wtr bwsr t dpt quvt t t s r dpt r cpctd 200 r tckss, s sw gur 11. step 8: r ws t cpctd t tckss d dst spcct ( tw rs rqurd) d curd ccrdg t r ct stbst spc ct. it ust b rbrd tt sgt v crrcts r rg ggrgt drg rks sud t b ttptd wt t r wdrwd tr, spc ct-trtd . s w rsu t rtv pr drd “bscu t r” wc w sw tpc bck crckg up dr g. it ws tcd, v s r s t xt d tr stb st, tt t stbsd r pprd d sudd uc rdr t wud b xpctd t suc r stg d cud b tr ckd b cstruct vcs wtut vsb dg. s s
9
10
13
14
I all goes according to current observations and predictions, this additive might well herald “crack-ree” cement stabilisation and improved and more economical utilisation o road building materials in the uture. Only uture application and behaviour monitoring with dierent materials will decide the outcome o this possibility dvtg ts ddtv wc, rgc, cud b utsd t ccdt rd trc. ( gr cstruct prgrss ws but 840 3 pr d.) vdc t r vg b ct stbsd, sv r s ut r d wd crcks s rs wr vrzus rg vrstrssd t st tp t r, ws t rd, st, scu d wtr-rsstt surc t r wc d cst ruct ctr strgt 2 t 4 mP wt sg t tpc ct stbst bck crckg (s gurs 12 d 13). s w s vr wc bsrvt sc t p bck crckg s ws b t jr drwbcks ct stbst, wc s d t urus tdts bg dvpd, t r ctv. o t r gc xpts r t bsrvd bsc crcks t prsc ts ddtv ss t b ts cd s trwvg crst structur, .. t rt ds s brc. it wud dd csttut jr brktrug suc crckg cud b prvtd r ctrd t gr dgr cr tt. T ctr sct wr ct stbsr ws usd dd t v t s k bscurs surc pprc t t s g. S s tr cud b brd d tpc ct stbst crckg ws vdt, s sw gur 14. step 9: bs ws t prd t rt but 0,75 / 2 d wd t dvp strgt. icdt, t ws td wt grt stsct tt t pr drd qut v d ptrtd t bs b 2 t 5 , sg tt t bs dst d s wr csstt d g qut . step 10: a 19 pus 9,5 prctd cp-d-spr dub s ws t ppd. (Sc t rg pvt ws gr t t s v r gr t t surrudg grud v, rtv tt rbtt wrk d t b d t surc drg tr t xtdg d sg pp cuvrts s cssr.)
N n
cts wr tcd b t wrkrs s rsut dg t PwrC. N u sprdg t ddtv dd t d cstruct prduct. N atug t prjct ws t d t d rct cprs dsg r stu strgt btw ct d ct pus RdC stbst, t rtv s w t wc t u dsg d stu strgts (gu r 6) wr btd s vdt t ucturr’s cs. N ddtv ss t v drtc dcrsd t ccurrc stbst crck g cprd t tt t ctr sct (ct ), wc s vrct t cd s p rtc trwvg prprts t ddtv. N s-but strgt su rts (gur 6) dct v tt w cpt cst-ctv wt crusd st t ts trc v, spc stb st crckg dvps r rc ts trug r t stbsd subbs. N i gs ccrdg t currt bsrvts d prdcts, t s ddtv gt w rd “crck-r” ct stbst d prvd d r cc uts t rd budg trs t utur. o utur ppct d bvur trg wt drt trs w dcd t utc ts pssbt.
rEFErENcEs COLTO (Committee o Land Transport Oicials) 1996. Structural design o lexible pavements or interurban and rural roads (Drat TRH 4 ). Pretoria: Department o Transport. Kleyn, E G 1975. The use o the Dynamic Cone Penetrometer (DCP). Pretoria: TPA Roads, Report L2/75. Kleyn, E G & Savage, P F 1982. The application o the Pavement DCP to determine the bearing properties and perormance o road pavements. Proceedings, International Symposium on Bearing Capacity o Roads and Airields, Trondheim, Norway, June. Marjanovic, P, Egyed, C, de La Roij, P & de La Roij, R 2009. Proceedings, RoadCem 2009, The Road to the Future, NUR-code 956, Netherlands. CONTACT DETAILS Victor de Freitas CEO: PowerCem Southern Arica
[email protected] Andrew Pauw MD: PowerCem Southern Arica
[email protected] in
[email protected] / www.powercem.co.za
ProJEcT sTaTUs ctrct s xpctd t b cptd nvbr 2010. at t t wrtg t ctrct d b rug r 11 ts, tr wrds t ws 58% cptd, d vrt g ws ru g ccrdg t p. n ds ttrbutd t tr vb t wr rgstrd. ct, csutt d ctrctr r prssd wt t wrkbt d vsu d structur rsu ts btd wt t ddtv.
coNclUsioNs wg ccuss wr d rgrdg t us t ct ddtv RdC ts rd grv stbst prjct:
011 974 7534/5
PROJECT TEAM
The Depart ment o Tran spor t, Roads and Co mmuni ty Sae ty o the North West Provincial Government is thanked or their permission to publish this article. The project team consisted o personnel rom the ollowing organisations: cent The Department o Transport, Roads and Community Saety o the North West Province Government cnutnt Mothibatsela and Associates cntt Kaulani Civils addtve uppe PowerCem South Arica
Dr Graham Howell Principal Engineer and Partner SRK Consulting
[email protected]
MARKET PERSPECTIVE
Innovation takes place at the
bunde f dpne While on a recent trip to Mali, SRK’s Dr Graham Howell was again struck by the importance of engineering disciplines working together, and agreed to share his thoughts with our readers
hRoUGhoU SCieniiC d grg str, jr brktrugs v tk pc w dscps v c tgtr r c bt d srg. Tk t dgs r xp - wt bt rct, i’ sur u cud cut “pur” dscps tt wr rqurd t k tt pssb. Wt s r prtt, tug, ws t sss trct btw t dscps. o ts ws cputr tcg wc 1969 ws sst ts c. T cputg pwr ts ds s b kd t wt s ur uzz gc wsg c td. But dd tt stp t dvur? Crt t! T ss c purps drv t prjct t succssu ccus. T trct btw t dscps d t pssb – css t r t t, d t st s td. it w srv s d r prjcts w d t t utur. W c r trdus ut but srgs busss d grg
r ts. T d dg tt t ‘w s bggr t t prts’ s crt trus rtr t r pt spc. hrssg t utpct dscps td’s grg ds s vt t sustb dvpt sttuts d csutcs k. Wt SRK w v wt dvrs tts tt r bg bc dvpd t sv prvus surutb prbs d t dvp w “prducts” r dustr purpss g d rsurc bct. lt us stp r t d csdr w ts cs but trug t r d r trg d xprc cc. i cv gr b r uvrst trg d spcs gtcc grg st d rd grud. m uvrst tr g cvrd t psc sccs (pscs d ppd ccs wt pur d ppd ttcs) wt sttrg cstr d cu td subjcts k structur, gtcc, druc d trsprtt grg wc drv tr udts r t ‘bs’ subjcts. at pst grdut v, i ws vvd wt ctuu ccs d dvcd structur ssts wc r strss-d-bsd, d c gtcc grg s d rct csquc. T rtsp btw structur d gtcc ssts s trr bvus t , but urk d bscur t trs. S d rck ccs
r prt t s ctuu tur trs tt r rqurd t b grd t fct supprt dustr d crc dvpt. Gg s cssr ds cp t udrstd d wd t tur prcsss cc supprt, rs d dpst prcsss d cut ccs tgtr. Sr, t ucs surc d grudwtr t structurs tt w bud r utst prtc. But i t ggst, r grudwtr spcst – i v t r xprts ts ds t bct prjcts – i d ggsts, grg ggsts d grudwtr xprts t ssst t udt trprtt. hc, t t tt ‘vt tks pc t t budrs dscps’ – trus tt s tk g pc ctu. m cgu, Grg mr o’rr, w s wt ts trp, s g gr. lk , s trg ws s t psc sccs t, but s cctrtd g prcsss d gt d spcss rd rck ccs, d prsss t kw tg but s ccs. i v ws r – trsc kws r t s wg t dt! Tt’s wr i c p. T tw us tgtr c cvr wd t dtd d d c up wt suts tt wud ud c us dvdu. Grg ss tt “wrkg tgtr s vr bc cbrtv dvur d s wd us t tk
uc r tr but t prjct s w rtr t b pg-d t rrw dscp. Prt t rs w t Sut arc rd rck g dustr, prtcur, s t vvd uc vr t pst 110 rs, s tt t g grs td t t csut wt tr dscps w dsgg g ut r td, prctc tt s b brd vr grts g grs t rg g uss. Trr, vtv tkg g grs td t v t prduct vrt t spcs tr g-rtd dscps. Ts prss vtu dvp t strtgc dvpt t brs, b t g us r csutc, s tr vtv tugt prcsss r stutd b t trct wt kws dd d vdus r tr dscps.” atr cs pt ccrs rct trp t Zb wr w dd t csdr ccptu dsg r str dvrs t prtct xstg d w r grudwtr d surc udt. our t csstd D, 80 Civil Engineering | April 2010
drggst; adr, gtcc gr, d s. i vr curtd trp w wr b t ssss t rsk t t xstg udrgrud, ct t rsks t t w udrgrud d p cst rs, csdr t xpctd ws t str d t qurs d prduc ur ccptu dsgs t ctr r t vtuts st. Ts ws pssb bcus t trct t tr us d t s rgs tt ts brugt but. idvdu , w wud t v d p cvrg t rqurts t ct suc srt t r, but cctv w wr pst t rspd t t cgs. ivt t t budrs dscps ws xtdd dgr tr tkg tt s t pssb dvdu. T cctv prsc cusd prb brgs sgts tt t surc trws. Sg t prb rst d s just s prtt r t cctv s w, sc t s zg bt prcpt tt ct b dqut dscrbd t cgus trug dscuss t fc r b w
ptgrps d prstts. s s t udrstd, wc sud b dg r grs rrspctv g r xprc. srgs s t vt d dvp r t dvdu, t cp, t prjct d t ct. m r wt SRK Csutg, wtr pct r xpct, s t str ts ts. Wtut vt d dvpt, grwt prs d busss v s t pssb, s w w ctu t ctvt ts psps t prjcts w d r t bt ur cts d ursvs. it s prtt t v sgs suc s “ivt ccurs t t budrs dscps” d “t w s bggr t t prts”. ec s drt tgs t drt pp trug tr prs xprcs, but utt t cctv put drvs sustb utur.
aDDiTioNal coNTacTs Greg More O’Ferrall: gmoreo
[email protected] Adriaan Meintjes:
[email protected] Diane Duthe:
[email protected] Tel: 011 441-1111
Rineshree Naidoo Associate Director BIGEN AFRICA Services (Pty) Ltd
[email protected]
BIGEN AFRICA ASKS:
ae Gvenment’ “Bekng New Gund” mxedmde ettement ddeng the hung bkg? he aim o Gvrt’s w u sttts pc s t cv rc, tgrtd sct trug t dvpt sustb sttts d qut usg tt w: N ccrt usg dvr d vt pvrt N us t prvs usg r jb crt d spt rstructur g N k prprt ccssb t crt wt, crs cc grwt d supprt t rsdt prprt rkt. T dvr usg Sut arc s b uc-dbtd ssu vr sc t prugt t husg act, act n 107, 1997. Dspt Gvrt’s rts d t 2,5 uss but durg t pst dcd, dvr s t t dd d t bckg st stds t pprxt 1,8 uss. it s vdt tt t xt dcd, dvpt prgrs ust k sgct rds t bt t usg d srvc dvr bckgs t cv Gvrt’s vs r vr ctz t j t st us wt ccss t ucp srvcs. i 2004, Gvrt’s prgrssv Brkg nw Grud dvpt strtg crtd trstg turrud Sut arc’s usg pc. agd wt t cvt Sut arc’s mu Dvpt Gs r vds, c, wtr d stt, t cus std r prvdg str t prvdg tgrtd, xdc sttts wt w-cst usg gsd dd-c rsdcs, wr bcrs v t s ccss t srvcs. T cg cg Gvrt t ptt ts pc, wvr, s t v t pg d crss vs Gvrt t drv cprt d cbrt, s tt td rsurcs r pt utsd.
mucpts ctgrs d t sks t dvp, t d dstr usg prjcts d srvc dvr, spcc t pg d ptt t xd-us dvpts. BiGen aRiCa prjcts drctr, St v Brk, currt prjct gr r t C mg itgrtd Dvpt Gutg, ss tt “w Gvrt s rspsb r usg pc dvpt t t t v, ucpts sud drv cg t t c v b su rg tt t v t sks t t pc bjctvs r tt ctv supprts t ds t bcrs t ctd cuts.” T C mg itgrtd Dvpt t mg Ct (Krugrsdrp) ucp r s gsp xd-us usg prjct r t prvc rsps t Gvrt’s Brkg nw Grud strtg. “BiGen aRiCa’s vvt ts prjct s cvcd us tt ts dvpts c p ucpts t vt tr usg d ucp srvcs bckgs. our srt busss pprc pr vdg ‘ bst brd’ grg sks tgrtd wt prjct c xprts, prgr gt, rs tructur sst gt d sttut grg, sss ts t tgrtd pprc t Brkg nw Grud strtg,” ss V Brk. T prjct s jt dvpt btw aBSa, t mg Ct lc mucpt d t Gutg Dprtt hu Sttts. it s rs prt aBSa’s usg dvr prgr, wc supprts t mrdu Udrstdg sgd btw Gvrt d t ur jr bks Sut a rc rsps t t drctv t c Sctr Crtr t vst w-cst, rdb usg.
Cstruct t rst ps t cv rstructur s cpt d tt t rst ps t ctrc rstructur s udr w. Cstruct t rst ps t tp structurs t dvpt w strt apr t s r. nt s t prjct ddrssg t usg bckg, but t s s prvdg pprtuts r pt d sks trg r pprxt 2 000 pp, w twtrds w b rsdt wt t mg Ct grtr ucp r. T dvpt w csst 9 315 rsdt uts, w t 4 244 subsdsd uts, 2 539 sttut usg uts d 2 532 rdb r-rkt (bdd) uss. “T xd-us ccdt crts vrt, xbt d vsu xctt,” ss Rs nd, prt gr r t prjct. “it s s cgc sud d w crt sustb vrt r t tr cut d crss vs c.” Spc cr ws tk t tgrt t xstg twsps azdv, Kgs d Rtv t p brdg t cc, srvc d sc rgtt. “W cbd vs wt prctct d xprc, usg bst prctc r u sttts d custsg suts r ts dvpt. W bv tt t rsut s uqu ccpt tt cpts t surrudg r d crss t ctr vu t usg stck.” tt prjct dvpt vu s sttd t r t b rd, wc w b udd trug vrus surcs pubc d prvt cg. nt w ts gsp dvpt rduc mg Ct’s usg bckg b r t trd, but t w s prvd rsdts wt wd cc usg d tur pts tt g w bd t trdt ccpt pr vd g str.
IN BRIEF
erometer (no cable connecting it to the PIT). All
sMallEr, WirElEss PilE iNTEGriTY TEsTEr UNVEilED: PiT-X
The works involved connecting ten o
unctions available on the latest edition o the
ABSA Bank’s buildings in the Johannesburg
PIT-V model have been preserved, including a
CBD with 100 underground sleeves or elec-
built-in Fast Fourier Transorm (FFT) eature that
tricity, gas, bre optics, low-temperature hot
is particularly helpul or detecting the length o
water and chilled water.
short oundation elements in the eld.
The ten-month contract had a value o
The company has also updated the PIT post-
R13 million. The contract document used was
processing/data analysis sotware, PIT-W, having
the NEC3. The project managers were Mokala
recently launched PIT-W 2009 in both Standard
Collins/JM Henrey & Associates Joint Venture, and
and Proessional versions.
the consultants were Taemane/SDE and Asak /LC.
Pile Dynamics, who has been manuac-
Horizontal directional drilling was done
PULSE ECHO INTEGRITY testing has or many
turing testing instruments or deep ounda-
rom building basement to building base-
years been the method o choice or quickly
tions or more than 35 years, is located in
ment beneath the busy CBD roadways at
veriying the integrity and length o deep
Cleveland, Ohio, USA, and has commercial
depths o up to 16 m. Sleeve diameters
oundations. Pile Dynamics rst developed an
representatives on all continents.
ranged in size rom 160, 225, 450, 500, 560 to 710 mm using PE 100 PN 8 HDPE pipe. The
instrument to per orm this test in 1991 – the Pile Integrity Tester (PIT). The device became
INFO
so popular that “PIT test” is oten used in lieu
www.pile.com
o “pulse echo test”. The method is also known
160 and 225 mm sleeves were installed in bundles o 3, 4 or 6 pipes. The award was presented to Sam Erat
as “low-strain dynamic oundation testing”, a
(managing member) and Marco Camarda
term used in the ASTM document that stand-
(general manager) o Trenchless Technologies
ardises it (ASTM D5882). The PIT test involves
cc at the SASTT Annual General Meeting by
placing an accelerometer on the oundation and hitting it with a handheld hammer. The accelerometer sends data to the PIT; records are visually evaluated immediately and later
TrENcHlEss TEcHNoloGiEs cc scooPs sasTT aWarD
analysed in urther detail. Pile Dynamics has recently launched the
the outgoing SASTT president, Mr Johann Wessels. The award ceremony was held at the regional ofces o Johannesburg Water in Midrand on 2 February 2010. The ABSA b uilding’s base ment lo ors
THE JOOP VAN WAMELEN South Arican
were originally designed to support the
PIT-X, a Pile Integrity Tester that ts in the palm
Society o Trenchless Technology (SASTT)
weight o a typical sedan car. Consequently
o one’s hand and works with a wireless accel-
Award o Excellence or 2009 was won by the
the Terra-Jet 7520’s automatic rod loading
ABSA energy centre sleeves reticulation project
system was removed to decrease the ma-
undertaken by Trenchless Technologies cc.
chine weight which was propped rom the
1
1
PIT-X wireless pile integrity tester
loor below to support all areas over which
remodelled drill resembled a tank with a
the ground anchor cables. In two instances
the drill needed to travel into the required
height o only 1,8 m.
the entangled cable would not break and
positions in the basements.
The majorit y o the installations were done
an oxy-acetylene cutter was modiied and
in clay, and 20 were in rock. The presence o
inserted in the bore to cut the cable and ree
required the height o all equipment to be
the rock necessitated the use o percussive
the drilling tools.
less than 2,1 m. Consequently the Terra-Jet
hammer and rock reamers to expand the holes
7520 was urther modiied by removing the
to the required diameters.
A loor-to-sprinkler height restriction
operator’s cabin, rebuilding the hydraulic
Lateral support ground anchors were en-
To gain access to the drill ace, coring to remove concrete lateral walls rom 300 to 500 mm thick was required.
oil tank at a lower position and lowering
countered during drilling on 26 o the cross-
the encapsulating bodywork such that the
ings. The presence and position o these
bentonite and spoil was necessary as the
were unoreseen, and resulted in the en-
basements are maintained in a pristine con-
Modiied Terra-Jet 7520 drilling
tanglement o drilling equipment in several
dition and are in daily use. This was made
in conined basement
instances. Drilling tools were pulled, pushed
possible using specially constructed tanks
and rotated until they came ree or broke
and brick burms.
1
2
Terra-Rock air percussion head
Containment o the large volumes o
The removal o b entoni te to the surace 1
was one o the greatest challenges the project aced. Initially pumping, which is by ar the preerred method o spoil removal, did not look easible. This was due to the extremely long pipe lengths (up to 600 m) that would have been needed to remove the bentonite rom basement to basement up the vehicle ramps. However, at the planning stage the idea was put orward to core holes through the slabs and to enable vertical pumping along the shortest route which would reduce pumping lengths to less than 200 m. For the rst six months o the contract no drilling was allowed during the “reeze period” rom the 26th o the preceding month to the 5th o the ollowing month. This was to prevent any potential damage to cables and inrastructure during the busy end-o-month banking period. This resulted in a very tight work schedule requiring crews to work day
2
and night shits seven days a week. The drilling equi pment had to be located on either side o the walls through concrete and rock at depths o up to 16 m. Trenchless Technologies used Radiodetection’s itrack system to track the equipment horizontally rom the basements on either side o each crossing. The conned access to the basements via vehicle ramps required short 6 m lengths o HDPE pipe to be individually transported down into the basements where they were butt-welded into long continuous lengths or installation. In the Museum the only access was by means o a lit and pipe lengths were limited to 3 m. Here, and in other conned storage areas and plant rooms, the bentonite was collected in tanks and wheeled out in “wheelie” bins. In two instances the HDPE pipe was hammered into the completed bore rom the drill machine side in a pipe ramming operation, as there was no access to pull the piping in rom the opposite side o the bore.
Proessor Fred Cawood, who has taken over the
strength to the lecturing sta. Proessors
which precluded conventional excavation
reins this year, says that mining has actually not
Phillips and Minnitt are still in the school, while
methods. There was no damage to roadways
seen better days.
Proessor Nielen van der Merwe, ormer head
The installations were exceptionally deep,
and existing buried inrastructure, nor was
He says that negative perceptions about
o the Mining Department at the University o
there any disruption to pedestrian and vehic-
the state o the industry are not hard to under-
Pretoria, joined the s chool as the Centennial
ular trafc in the busy CBD area. Cost savings
stand: “Mining is not called a boom-and-bust
Chair o Rock Engineering at the end o
were also signicant when compared to other
industry or nothing. Reserves run out at a
January. Proessor Dick Stacey is still lecturing
possible methods.
specic geographic location under specic
students in a part-time capacity. The services
economic and technical conditions.” But this
o Proessor May Hermanus and Dirk Bakker,
lowed the insertion o the preerred HDPE
only underlines the vital role o universities in
both ormer Chie Inspectors o Mines, have
sleeves without the installation o a tempo-
the supply o skilled graduates – in geology,
also been secured through the Centre or
rary pipe or permanent rigid pipe, ollowed
or instance, to nd new ore bodies, and in the
Sustainability in Mining and Industry (CSMI),
by the HDPE pipe installation. HDD required
case o mining engineers, to enable them to
which is an important part o the school’s u-
no thrust abutment wall and also allowed
work smarter so that we can sustain mining as
ture research plans.
adequate steering accuracy. The equipment
a business.
Horizontal directional drilling (HDD) al-
The dan ger, says Pro Cawo od, is that i
is sel-propelled and capable o drilling in
Pro Cawood leads the discipline o
a wide range o soil t ypes including clay
mine surveying at the school and is currently
tant sta resources, the result will inevitably
and rock. It is also suiciently compact and
President o the Institute o Mine Surveyors
be a higher drop-out rate. The school is
manoeuverable to be able to operate in the
o South Arica. His work on mining royalties
already working on ways to keep more stu-
conined basement spaces.
has had a signicant impact in South Arica:
dents moving successully rom one year to
the National Treasury based the country’s new
the next, and has enlisted the sponsorship
royalty system on the ormula he developed in
o the SA Institute o Mining and M etallurgy
his doctoral thesis.
among others or tutors, extra copies o cru-
INFO Sam Erat Trenchless Technologies cc 083 212 4888
[email protected]
As well as publishing widely on mineral resources management, mine surveying and
cial books and vital equipment. Nowhere is the commitment to growing
mining policy matters, he co-authored the 2006
the school’s capacity more evident at the
World Bank Mining Royalties book – a compre-
moment than in the building works that char-
hensive guide to the collection and manage-
acterise the Wits campus – a ourth quadrant is
ment o royalties internationally.
being added to the Chamber o Mines Building
His contribution is also elt throughout
MiNiNG aliVE aND WEll saYs NEW WiTs scHool HEaD
classes are allowed to grow without concomi-
Arica. As a member o the United Nations
and existing space is being renovated. Despite the difculty in attracting sta
International Study Group, he has helped de-
in the current environment, Pro Cawood is
velop strategies or the improved use o mineral
positive about the school’s ongoing contribu-
resources in Arica. And within the Southern
tion to transormation at the university, in the
Arican Development Community (SADC), he
industry and in society. “Our student body
WITS UNIVERSITY HAS a new head o its School
assists several governments in mining policy
has changed rom nearly all white to nearly
o Mines, and he gives short shrit to any sug-
and taxation matters.
all black, and rom almost e xclusively male to
gestions that mining may be a dying industry. Pro Fred Cawood, new head o the School o Mining Engineering, University o the Witwatersrand
Judging by the school’s student numbers, it
more than 30% emale,” he s ays. “Judging by
is hard to disagree with Pro Cawood about the
the interest rom school leavers in mining as
interest in mining’s uture. Last year, some 468
a career choice, I am convinced that we will
undergraduate students and 285 postgradu-
have a signicant mining industry or a very
ates were enrolled; this year, over 200 students
long time to come.”
registered to do rst-year studies (straining the department’s ofcial capacity o about 150).
INFO
While the school develops strategies to
Sally Braham
deal with the demand or training, the industry
[email protected]
expects a constant ow o exper tise to ull the demands o a mo dern and constantly changing work environment. His main challenge is to nd and retain the best sta possible, in line with the rising number o students – no mean eat, as industry will lure away experts whenever the economic cycle avours mining expansion. “We have to try to attract sta when industry is retrenching, and then have a retention strategy to prevent high
asH rEsoUrcEs laUNcHEs “NEW GENEraTioN” cEMENT EXTENDEr
sta turnover when the industry is experiencing boom times,” he says.
This year the school will benet rom having six proessors provide academic
ASH RESOURCES HAS introduced a new improved perormance-classied y ash, DuraPozz Pro, to the local market.
The company’s products, which or more than 30 years have been successully used as
spherical – particles results in more dense and
reclaim more habitable surace area or
durable concrete,” says Sheath.
building low-cost homes near Kayamandi,
cement extenders, are by-products rom the
He says that DuraPozz Pro provides the ol-
an inormal settlement in the vicinity o
generation o electricity at Eskom coal-red
lowing advantages in resh or plastic concrete:
power stations.
N
Reduced water content
Terra orce retaining blocks were deci ded
N
Improved workability
on, as they provide a cost-eective, yet
Manager or Ash Resources, says the new cement
N
Increased pumpability
durable method or creating platorms and
extender, DuraPozz Pro, which is produced at the
N
Better concrete compaction
road/sidewalk support on the old armland
Ash Resources plant at Matla in Mpumalanga,
For hardened concrete, the benets include:
“takes the unrivalled perormance and track
N
Increased strength gain over time
to amilies who are currently living on what
record o Ash Resources’ classied y ash,
N
Lower heat o hydration
will eventually become the parking area or
DuraPozz, to new heights – at no extra cost to
N
Reduced shrinkage
the upgraded Kayamandi sports ield and
the end-user.”
N
Reduced permeability leading to improved
Touris m Cent re.
John Sheath, Strategy and Marketing
Sheath explains: “DuraPozz Pro is a ‘new generation’ classied y ash or high-perormance, high-durability concrete. It has been designed
durability N
Stellenbosch. Ater some consideration,
earmarked to provide 380 emergency homes
Says Henk van Renssen, project engineer
Smoother, more attractive nishes and aes-
with Arcus Gibb, the engineering and science
thetics
consulting company involved in the project:
and developed or the proessional end-user
“By taking the y ash rom Eskom’s bituminous
“The site, called TRA2 (Temporary Relocation
who requires concrete with added strength and
coal-red power stations, and engineering this
Area 2), orms part o the bigger Watergang
durability.”
by-product’s benecial use, Ash Resources prod-
Housing Project and will soon be home to
ucts – such as carbon-lean DuraPozz Pro – rank
380 amilies who need to be relocated so
high in the quest or sustainable construction
that urban upgrading can take place in the
Improved concrete workability and water
and the reduction o greenhouse gas emissions,”
area. The homes, or now consisting o basic
reduction as a result o its neness, spherically
Sheath adds.
wooden structures, will eventually give way
Some o the many benets o DuraPozz Pro include: N
shaped particles and unique particle size
to 100 permanent homes. The goal is to INFO
distribution N
DuraPozz Pro concrete, with its lower water-
John Sheath
cement ratio, has decreased permeability
011 886 6200
which results in reduced chloride and sulphate
www.ashresources.co.za
attacks and reduced alkali-silica reactivity N The
N
provide more ormal housing in the long run, while improving the general environs.” The retaining blocks used at th e Kayamandi site were pioneered by Terraorce – a Cape Town-based precast concrete
lubrication action o the new product
licensor – 30 years ago and represent one
reduces water content and drying shrinkage
o the most energy-eicient segmental
in concrete
retaining wall systems. Says Jeremy Leighton
Higher strength evolution over time
o Cape Retaining Systems: “What makes this
The product is suitable or use by concrete proessionals across the whole o the concrete industry. DuraPozz Pro particle size is a ner grade than required by SANS 1491:Part 2 Portland
local rETaiNiNG BlocK assisTs WiTH UPGraDiNG oF iNForMal sETTlEMENTs
Cement Extenders: Fly Ash specication. “The concentration o the extremely ne – and 1
Ash Resources’ new DuraPozz Pro classied fy
ash is produced at the company’s Matla plant
product so popular in the industry is that the blocks require low hardware input or manuacture, and have low transport costs and low inventory requirements at sales outlets. They are hollow, yet strong enough, and require less concrete to do the job when
IN MARCH 2009, Cape Retaining Systems,
compared with solid block systems, which o
the Cape-based retaining block manuac-
course saves money.”
turer and Terraorce licence holder, was approached by Requad Construction to
He adds that: “Concrete retaining walls constructed using the Terraorce system are easily ormed into complex curved shapes or
1
into walls in which the upper and lower proiles are continuously changing. The system also allows you a choice between round ace (plant supportive) or lush ace (smooth or split version) to suit speciic requirements. Above all, they present a closed vertical surace structure that provides the maximum amount o soil mass within the wall, which prevents backill spillage, while at the same time oering uninhibited permeability.” The r st concre te ound ations at Kayamandi were laid in November 2009. Each o the three walls is tted with a 110 mm subsoil drainage pipe that runs along the entire length o the wall and exits through weep holes cut into individual blocks at regular
intervals. As the walls were built up, a sand
N
Gravity retaining walls as and when
drainage layer o 500 mm was lled to the top
required or road widening or improved
to prevent possible damming up o water.
stormwater drainage
A similar project using Terraorce blocks
N
was initiated by the Swaziland Ministry o Urban Development to provide urban
Drit crossings and weirs across small
ciTY oF caPE ToWN lEaDs THE WaY iN sErVicE DEliVErY
streams Hard suraces (Terracrete blocks) at various
THE CIT Y OF CAPE TOWN has o nce a gain
upgrading in the suburbs around Mbabane,
strategic locations or parking reuse col-
been rated as the top metropolitan munici-
where steeply sloping and easily erodible
lection bins.
pality in South Arica or service delivery
N
topography in a high-rainall area posed
According to Michael Toeper, owner o
by Empowerdex, South Arica’s leading
some unique challenges to the local town
Milito Precast, Terraorce products provided
economic empowerment rating and re-
planners. To prevent urther serious damage
cost-eective, environmentally environmentally sound solu-
search agency. This annual survey measures
to the environment, remedial measures were
tions, as well as job opportunities: “The
delivery in the areas o housing, water,
carried out, using manual labour as much as
blocks are manageable enough to allow
electricity, waste removal and sanitation and
possible. Terraorce L11 blocks and Terracrete
manual labour to be used to install them
covers 231 local, 46 district and 6 metro-
hard lawn blocks, supplied by Milito Precast
and many unemployed locals managed to
politan municipalities. municipalities.
o Manzini, were ound to be ideal or pro-
ind work during the construction period.
viding the ollowing:
Because lots o smaller walls were built,
ously maintain and escalate its high levels
Stormwater drainage channels (Terracrete
no heavy machinery was required and the
o perormance, the City has acquired ully
blocks), illed with soil or soilcrete, de-
locals, armed with a shovel and pick, were
integrated integrated inrastructure design sotware
pending on the anticipated velocity or
able to lay the blocks themselves. The
platorms to the value o R1,74 million.
volume o water low
workorce came directly out o the inormal
The so twa re, d evel ope d an d sup plie d
Cascades, stilling basins and small diver-
settlements, and they were monitored and
by Knowledge Base, has been used in the
sion weirs, illed with soil or concrete as
trained by recommended contractors and
design o signiicant inrastructure projects
required
supervisors.”
in the city such as the Green Point Stadium,
N
N
In keeping with its policy to continu-
M5/Koeberg Interchange, IRT System and 1
1
A Terraorce Terraorce wall wall creating creating a level
INFO
Hospital Bend.
platrom or emergency emergency housing and and roads
Karin Johns
Ater an extensive evaluation o the
in Kayamandi, Stellenbosch. Here the wall
Marketing Manager – Terraorce
Knowledge Base sotware and its com-
runs around a stormwater drain
karin@terraorce.com
petitor products, Civil Designer & AllyCAD
PermPave Version 2.1 and LockPave
1
Version 18.1 are available on a single disc at no charge to existing users and at a nominal R500,00 or new users. First launched in 2008, PermPave is a sotware package aimed at assisting civil engineers and landscape architects in the design o PCBP systems. LockPave was rst launched in the 1990s or the design o CBP systems. Both packages were authored by Dr Brian Shackel, but PermPave was developed in collaboration with Proessor Simon Beecham o the University o South Australia. Both systems can be used or various paving products and locations, and this provides considerable design scope. PermPave is programmed with South Arican rainall data and allows or the urther downloading o local climate and rainall inormation. “It acilitates the selection o paving blocks best suited to a particular application. Moreover, it allows water requirements and volumes to be specied, either or storage and re-use or or replenishing underground water tables,” advises Shackel. 1
Cape Town – rated by Empowerdex
as the top metropolitan municipality municipality in South Arica or service delivery
were selected to help develop the capacity
UPDaTED PErMEaBlE PaViNG PaViNG DEsiGN soFTWarE aVailaBlE FroM THE cMa
Based in Sydney, Australia, Dr Shackel has worked on many projects worldwide as a consultant or asphalt paving, block paving and r igid concrete pavements. He is a recognised authority on CBP and is the author o numerous research papers and three books on this topic. His work on CBP suraces won him an Award or Excellence
and perormance o the City’s in-house design team in an eort to reduce outsourcing
UPDATED UPDATED VERSIONS o PermPave, sotware
costs, and to optimise time and project
used or designing permeable concrete
management.
block paving (PCBP) suraces, and LockPave,
o Sustainable Water Resources Engineering in
sotware used or designing conventional
the School o Natural and Built Environments
Civil Designer is a sotware platorm that
rom the Concrete Institute o Australia. Proessor Beecham is currently Proessor
consists o a suite o ully interactive design
concrete block paving (CBP) suraces, are now
(NBE) at the University o South Australia and
modules that combine to orm an integrated
available rom the Concrete Manuacturers
has been work ing with UNISA’s Water Science
data gathering, drawing, surace modelling
Association (CMA).
and Systems Centre. .
and design system or civil engineering 1
inrastructure. AllyCAD is an intuitive, user-
The eectiveness o a PCBP system can be
riendly 3D draughting package with special-
seen in this example at the Grand Parade in
ised toolkits or the architectural, architectural, surveying
Cape Town – PCBP surace in the oreground
and engineering ields.
contrasting with conventionally paved surace
With 2010 inrastructure development on track, the City will use the sotware applications in the rollout o similar exciting projects in the uture. Says CEO o K nowledge Base, Vincent Bester, “This is an exciting partnership and we are very happy to have the City o Cape Town com e on boa rd. We lo ok orward or ward to a long and prosperous relationship and urther congratulate the City o Cape Town on their excellent perormance in terms o service delivery.” INFO Knowledge Base Sotware www.knowbase.co.za
1
INFO Pam (at CMA) 011 805 6742
[email protected]
SAICE AND PROFESSIONAL NEWS
More courses rom the
cnddte ademy The newly launched Candidate Academy will roll out its next two new courses in May and June to support graduates with the transition from theory to application in the workplace
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New SAICE
Few Bruce Raath attended the Durban High School and graduated rom the University o KZN. His career embraced several dierent disciplines
www.cesa.co.za
and culminated in a partnership
Or contact the ollowing people:
at Contest Concrete Technology
Dawn Hermanus (SAICE)
Services. He recently retired rom the
011 805 5947
C&CI (Concrete and Cement Institute)
[email protected] Brenda Lacey-Smith (CESA) 011 463 2022
[email protected]
where he ran the education division. He was closely involved with the Durban Branch o SAICE and served many years as secretary. He is still active in the SAICE and sits on the JSD
Course: Basic Contract Management and Quality Control
Date
committee. He holds qualiications Venue
3 – 5 May 2010
SAICE National Ofce, Midrand
17 – 19 May 2010
Cape Town (venue to be advised)
26 – 28 July 2010
Durban (venue to be advised)
23 – 25 August 2010
SAICE National Ofce, Midrand
rom the Association o Arbitrators, as well as the Advanced Concrete Techno log y Di ploma a ward ed by Imperial College, University o London. He is currently consulting in all aspects o concrete technology and usage, and is also training young
Course: Basic Pressure Pipeline Design
Date
engineers. He is married to Judy and Venue
1 – 2 June 2010
SAICE National Ofce, Midrand
20 – 21 Sept 2010
Durban (venue to be advised)
11 – 12 October 2010
SAICE National Ofce, Midrand
the couple have two children.
