This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D5778 − 12
Standard Test Method for
Electronic Friction Cone and Piezocone Penetration Testing of Soils1 This standard is issued under the fixed designation D5778; the number immediately following the designation indicates the year of original origin al adoption or, in the case of revis revision, ion, the year of last revision. revision. A number in paren parenthese thesess indicates the year of last reappr reapproval. oval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
agreed agre ed to by th thee cli clien entt or us user er.. Co Cone ne tip projec projected ted area is commonly referred to in square centimetres for convenience. The values stated in each system are not equivalents; therefore, each system shall be used independently of the other.
1. Sco Scope* pe* 1.1 This test method covers the procedure procedure for determ determining ining the poi point nt res resista istance nce dur during ing pen penetr etratio ation n of a con conical ical-sh -shape aped d penetrometer as it is advanced into subsurface soils at a steady rate.
NOTE 1—This test method does not include hydraulic or pneumatic penetrometers. penetrometer s. Howev However, er, many of the proce procedural dural requirements requirements herein could apply to those penetrometers. Also, offshore/marine CPT systems may have procedural differences because of the difficulties of testing in those environments environments (for example, tidal variati variations, ons, salt water water,, waves waves). ). Mechanical Mecha nical CPT syste systems ms are covered under Test Test Metho Method d D3441 D3441..
1.2 This test method is also used to determine determine the frictional resistance resista nce of a cyl cylind indrica ricall slee sleeve ve loc located ated beh behind ind the con conical ical point as it is advanced through subsurface soils at a steady rate. 1.3 This test method applies to frictio friction-con n-conee penetr penetrometer ometerss of th thee el elec ectr tric ic an and d el elec ectr tron onic ic ty type pe.. Fi Fiel eld d te test stss us usin ing g mechanical-type penetrometers are covered elsewhere by Test Method D3441 Method D3441..
standard d doe doess not purport purport to add addre ress ss all of the 1.8 This standar safet sa fetyy co conc ncern erns, s, if an anyy, as asso socia ciated ted wit with h its us use. e. It is th thee responsibility of the user of this standard to establish appro priate safety and health practices and determine the applicability of regulatory limitations prior to use.
1.4 Thi Thiss test method method can be use used d to det determ ermine ine porewater porewater pressures developed during the penetration, thus termed piezocone. Porewater pressure dissipation, after a push, can also be monitor mon itored ed for cor correla relatio tion n to time rat ratee of con consol solida idatio tion n and permeability.
2. Referenc Referenced ed Documents 2.1 ASTM Standards: 2 D653 Termino erminology logy Relating to Soil, Rock, and Contain Contained ed Fluids D3441 Test D3441 Test Method for Mechanical Cone Penetration Tests of Soil (Withdrawn Soil (Withdrawn 2014) 3 D3740 Practic Practicee for Minimu Minimum m Requir Requirements ements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction D7400 Test D7400 Test Methods for Downhole Seismic Testing E4 Practices for Force Verification of Testing Machines E4
1.5 Addit Additional ional sensors, sensors, such as inclin inclinometer ometer,, seismic geophones phon es (T (Test est Me Metho thods ds D7400), D7400 ), resi resistiv stivity ity,, elec electrica tricall conduc con ductiv tivity ity,, die dielect lectric ric,, and tem temper peratu ature re sen sensor sors, s, may be included includ ed in the penetr penetrometer ometer to prov provide ide usefu usefull infor information mation.. The use of an inclinometer is highly recommended since it will provide information on potentially damaging situations during the sound sounding ing proce process. ss. 1.6 1. 6 Co Cone ne pe pene netr trati ation on tes testt da data ta can be us used ed to in inter terpr pret et subsur subs urfa face ce str strati atigr grap aphy hy,, an and d th thro roug ugh h us usee of sit sitee sp speci ecific fic correlations, they can provide data on engineering properties of soils intended for use in design and construction of earthworks and found foundations ations for struct structures. ures.
3. Terminology 3.1 Definitions: 3.1.1 Definit Definitions ions are in accordance accordance with Termino Terminology logy Convention (D653 D653)). 3.2 Definitions of Terms Specific to This Standard: 3.2.1 apparent load transfer— apparent apparent resistance measured on either the con conee or fri frictio ction n sle sleeve eve of an elec electro tronic nic cone penetrometer while that element is in a no-load condition but
1.7 Th 1.7 Thee va valu lues es sta stated ted in SI un units its are to be re rega gard rded ed as standar stan dard. d. Wi Within thin Section Section 13 on Calc Calcula ulation tions, s, SI uni units ts are considered the standard. Other commonly used units such as the inch-pound system are shown in brackets. The various data reported should be displayed in mutually compatible units as 1
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This test method is under the jurisdiction jurisdiction of ASTM Committee D18 Committee D18 on on Soil and Rock and is the direct responsibility of Subcommittee D18.02 on Sampling and Related Field Testing for Soil Evaluations. Current Curre nt editio edition n approv approved ed Jan. 1, 2012. Published Published Februa February ry 2012. Originally Originally approved approv ed in 1995. Last previous previous edition approved in 2007 as D5778– D5778–07. 07. DOI: 10.1520/D5778-12.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at
[email protected]. For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website. 3 The last app approv roved ed ver versio sion n of this historica historicall sta standa ndard rd is ref refere erence nced d on www.astm.org.
*A Summary of Changes section appears at the end of this standard Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D5778 − 12 fricti ction on ra ratio tio,, R f — the 3.2.15 fri t he ra rati tio o of fr fric icti tion on sl slee eeve ve resistance, f s, to con conee res resista istance nce,, qc, measured at where the middle of the friction sleeve and cone point are at the same depth, expressed as a percentage.
the other element is loaded. Apparent load transfer is the sum of cross talk, subtraction error, and mechanical load transfer. 3.2.2 baseline— a set of zer zero o loa load d read reading ings, s, exp expres ressed sed in terms of apparent resistance, that are used as reference values during performance of testing and calibration.
NOTE 2—Some methods to interpret CPT data use friction ratio defined as the ratio of sleeve friction, f s, to cone resistance corrected for pore pressure press ure ef effects fects q t, (1). It is not wi with thin in th thee sc scop opee of this standa standard rd to recommend which methods of interpretation are to be used.
3.2.3 cone tip— the the conical point of a cone penetrometer on which the end bearing component of penetration resistance is developed. The cone has a 60° apex angle, a diameter of 35.7 mm, and a corresponding projected (horizontal plane) surface area or cone base area of 10 cm 2. Also, enlarged cones of 43.7 mm diameter (base area = 15 cm2) are utilized.
3.2.16 friction reducer— a narrow local protuberance on the outside of the push rod surface, placed at a certain distance above the penetrometer tip, that is provided to reduce the total side friction on the push rods and allow for greater penetration depths for a given push capacity.
3.2.4 cone penetration test— a series of penetration readings performed at one location over the entire vertical depth when using a cone penetrometer. penetrometer. Also referred referred to as a cone sounding. sounding.
3.2.17 friction sleeve— an an isolated cylindrical sleeve section on a penetrometer tip upon which the friction component of penetra pen etratio tion n res resista istance nce dev develo elops. ps. The fri frictio ction n sle sleeve eve has a 2 2 surface area of 150 cm for 10-cm cone tips or 225 cm 2 for 15-cm2 tips.
3.2.5 cone penetrometer— a penetrometer penetrometer in which the leading end of the penetrometer tip is a conical point designed for penetrating soil and for measuring the end-bearing component of penetr penetration ation resista resistance. nce.
3.2.18 friction sleeve resistance, f s — the the friction component of penetration resistance developed on a friction sleeve, equal to the shear force applied to the friction sleeve divided by its surface surfa ce area.
3.2.6 cone resistance, q c — the the measured end-bearing component of penetration resistance. The resistance to penetration developed on the cone is equal to the vertical force applied to the cone divided by the cone base area.
3.2.19 FSO— abbreviation abbreviation for full-scale output. The output of an electronic force transducer when loaded to 100 % rated capacity.
3.2.7 corrected total cone resistance, q t — tip tip resistance corrected for water pressure acting behind the tip (see 13.2.1). 13.2.1). Correction for water pressure requires measuring water pressures with a piezocone element positioned behind the tip at location u2 (See (See sec section tion 3.2.26) 3.2.26). Th Thee co corr rrec ectio tion n re resu sults lts in estimated total tip resistance, qt.
local al sid sidee fri fricti ction on— — same 3.2.20 loc s ame as fr fric icti tion on sl slee eeve ve resistance, f s (see (see 3.2.18 3.2.18). ).
3.2.21 penetration resistance measuring system— a measuring system that provides the means for transmitting information from the penetrometer tip and displaying the data at the surface where it can be seen or recorded.
3.2.8 cross talk— an an apparent load transfer between the cone and the fri frictio ction n sle sleeve eve cau caused sed by inte interfe rferen rence ce bet betwee ween n the separate separa te signa signall channe channels. ls.
3.2.22 penetrometer— an an apparatus consisting of a series of cylindrical push rods with a terminal body (end section), called the penetrometer penetrometer tip, and measur measuring ing devices for determ determinatio ination n of the components of penetration resistance.
electronic cone penetr penetrometer ometer— — a fr 3.2.9 electronic frict ictio ion n co cone ne pe pennetrometer that uses force transducers, such as strain gauge load cells, cel ls, bu built ilt in into to a no nonn-tel teles esco copi ping ng pe pene netro trome meter ter tip fo forr measuri meas uring, ng, wit within hin the pen penetro etromete meterr tip tip,, the com compon ponent entss of penetration resistance.
3.2.23 penetrometer tip— the the terminal body (end section) of the penetrometer penetrometer which contai contains ns the active elements that sense the components of penetration resistance. The penetrometer tip may includ includee additi additional onal electronic instru instrumentat mentation ion for signal conditioning and amplification.
electronic nic piezocon piezoconee penetr penetrometer— ometer— an 3.2.10 electro an elec electron tronic ic cone penetrometer equipped with a low volume fluid chamber, porous element, and pressure transducer for determination of porewater pressure at the porous element soil interface measured simultaneously with end bearing and frictional components of penetration resistance.
3.2.24 piezocone— same same as electronic piezocone penetrometer (see 3.2.10 (see 3.2.10). ). piezocone cone por porewate ewaterr pr pressu essure re,, u— fluid 3.2.25 piezo fluid pres pressure sure measured using the piezocone penetration test.
3.2.11 end bearing resistance— same same as cone resistance or tip resist resistance, ance, q c.
3.2.26 piezocone porewater pressure measurement location: u1 , u 2 , u 3 — fluid fluid pressure measured by the piezocone penetrometer at specific locations on the penetrometer as follows ( (2 2, 3 3,, 4 4) : u1—porous filter location on the midface or tip of the cone, u2—porous filter location at the shoulder position behind the conee tip (st con (stand andard ard loc locatio ation) n) and and,, u3—poro —porous us filter locatio location n behind the friction sleeve.
3.2.12 equilibrium at rest water equilibrium por poree water pr pressur essure, e, u0 — at pressure at depth of interest. 3.2.13 excess pore water pressure, ∆u— the the dif differen ference ce between porewater pressure measured as the penetration occurs (u), and estimated equilibrium porewater pressure (u 0), or: ∆ or: ∆u u = (u – u 0). Excess porewater pressure can either be positive or negative for shoulder position filters.
3.2.27 porewater pressure— total total porewater pressure magnitude measured during penetration (same as 3.2.25 3.2.25 above). above).
friction n cone penetr penetrometer ometer— — a con 3.2.14 frictio conee pen penetr etrome ometer ter with the cap capabi ability lity of meas measuri uring ng the fri frictio ction n com compon ponent ent of penetration resistance.
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The boldface numbers given in parentheses refer to a list of references at the end of the text.
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D5778 − 12 3.2.28 porewater pressure ratio parameter, B q — the the ratio of excess porewater pressure at the standard measurement location ∆u2, to corrected total cone resistance qt , minus the total vertical overburden stress, σ vo (see (see Eq Eq 10). 10).
5. Signi Significanc ficancee and Use 5.1 Test estss per perfor formed med using this tes testt met method hod provide provide a detailed record of cone resistance which is useful for evaluation of site str stratig atigrap raphy hy,, hom homoge ogenei neity ty and dep depth th to firm lay layers ers,, voids or cavities, and other discontinuities. The use of a friction sleeve and porewater pressure element can provide an estimate of soil classification, and correlations with engineering properties of soils. When properly performed at suitable sites, the test provides a rapid means for determining subsurface conditions.
3.2.29 push rod the thick-wal thick-walled led tubes or rod rodss use used d to rods— s— the advance the penetrometer tip. resistance— — same 3.2.30 sleeve friction, sleeve, and friction resistance same as friction sleeve resistance.
3.2.31 subtraction error— an an apparent load transfer from the cone to the friction sleeve of a subtra subtraction ction type electronic electronic cone penetrometer penetr ometer caused by minor voltage dif differen ferences ces in respo response nse to load between the two strain element cells.
5.2 Th 5.2 This is tes testt me meth thod od pr prov ovid ides es da data ta us used ed fo forr es estim timat atin ing g engineering properties of soil intended to help with the design and construction of earthworks, the foundations for structures, and the behavior of soils under static and dynamic loads.
3.3 Abbreviations: 3.3.1 CPT— abbreviation abbreviation for the cone penetration test.
5.3 Thi Thiss meth method od tests the soi soill inin-situ situ and soil samples samples are not obtained. The interpretation of the results from this test method meth od pro provid vides es esti estimate matess of the typ types es of soi soill pen penetr etrated ated.. Engineers may obtain soil samples from parallel borings for correlation purposes but prior information or experience may preclude the need for borings.
abbreviation for piezocone 3.3.2 PCPT (2 ( 2, 3 3)) or CPTu ( (4 4) — abbreviation penetration test (note: symbol “u” added for porewater pressure measurements). 3.3.3 CPTù— abbreviation abbreviation for the piezocone penetration test with dissipation phases of porewater pressures (ù).
NOTE 3—The 3—The qua quality lity of the res result ultss pro produc duced ed by thi thiss sta standa ndard rd is dependent on the competence of the perso dependent personal nal performing performing the test, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 Practice D3740 are are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 Practice D3740 does not in itself assure reliable reliab le result results. s. Reliable results depend on many factors and Pract Practice ice D3740 provides D3740 provides a means of evaluating some of those factors.
3.3.4 SCPTu— abbreviation abbreviation for seismic piezocone test Test Methods D7400 (inclu (includes des one or mor moree geo geopho phones nes to allo allow w downhole downh ole geoph geophysical ysical wave velocit velocity y measur measurements) ements).. 3.3.5 RCPTu— abbrev abbreviati iation on for res resisti istivity vity pie piezoc zocone one (in (in-cludes electrical conductivity or resistivity module). 4. Summ Summary ary of Test Test Method
6. Interfere Interferences nces
4.1 A penetro penetromete meterr tip with a con conical ical point point hav having ing a 60° 2 apex angle and a cone base area of 10 or 15 cm is advanced through the soil at a constant rate of 20 mm/s. The force on the conical point (cone) required to penetrate the soil is measured by ele electr ctrica icall me meth thod ods, s, at a mi mini nimu mum m of ev ever ery y 50 mm of penetration. penetr ation. Improved Improved resolution may often be obtain obtained ed at 20or 10-mm interval readings. Stress is calculated by dividing the measure meas ured d for force ce (to (total tal cone for force) ce) by the cone bas basee area to obtain cone resistance, qc.
6.1 Refusa Refusal, l, deflection, or damage to the penetrometer penetrometer may occur in coarse grained soil deposits with maximum particle sizes that approach or exceed the diameter of the cone. 6.2 Parti Partiall ally y lit lithi hified fied and lit lithi hified fied de depo posit sitss ma may y cau cause se refusal, deflection, or damage to the penetrometer. 6.3 Stan Standar dard d pus push h rod rodss can be dam damage aged d or bro broken ken under extreme loadings. The amount of force that push rods are able to sustain is a function of the unrestrained length of the rods and the weak links in the push rod-penetrometer tip string such as push rod joints and push rod-penetrometer tip connections. Thee fo Th forc rcee at wh whic ich h ro rods ds ma may y br brea eak k is a fu func ncti tion on of th thee equipment equip ment config configuratio uration n and groun ground d condi conditions tions during penetration. Excessive rod deflection is the most common cause for rod breakage.
4.2 A friction friction sleeve is presen presentt on the penetrometer penetrometer immediately behind the cone tip, and the force exerted on the friction sleeve slee ve is mea measur sured ed by elec electric trical al meth methods ods at a min minimu imum m of every 50 mm of penetration. Stress is calculated by dividing the measured axial force by the surface area of the friction sleeve to determine sleeve resistance, f s.
7. Appar Apparatus atus
4.3 Most modern penetrometer penetrometerss are capable of regis registering tering pore water pressure induced during advancement of the penetrometer etromet er tip using an electro electronic nic pressu pressure re transd transducer ucer.. These penetrometers are called “piezocones.” The piezocone is advanc va nced ed at a ra rate te of 20 mm mm/s, /s, and re read adin ings gs are tak taken en at a minimum of every 50 mm of penetration. The dissipation of either positive or negative excess porewater pressure can be monitored by stopping penetration, unloading the push rod, and recordi reco rding ng por porewa ewater ter pre pressu ssure re as a fun functio ction n of time time.. Whe When n pore po rewa water ter pr pres essu sure re be beco come mess co cons nstan tantt it is me measu asuri ring ng th thee equilibrium value (designated u 0) or piezometric level at that depth.
Friction n Cone Pene Penetr tromet ometer— er— The 7.1 Frictio T he pe penet netro romet meter er tip should meet requirements as given below and in 10.1. 10.1. In a conventional friction-type cone penetrometer, the forces at the cone tip and friction sleeve are measured by two load cells within wit hin the pen penetr etrome ometer ter.. Eith Either er ind indepe epende ndent nt loa load d cell cellss or subtractionsubtr action-type type penetrometers penetrometers are accepta acceptable ble for use ( Fig. 1). 1). 7.1.1 7.1 .1 In the sub subtra tractio ction-t n-type ype pen penetro etromete meter, r, the con conee and sleeve both produce compressive forces on the load cells. The load cells are joined together in such a manner that the cell near ne ares estt th thee co cone ne (t (the he “C “C”” ce cell ll in Fig. Fig. 1b) me meas asur ures es th thee comp co mpre ress ssiv ivee fo forc rcee on th thee co cone ne wh while ile th thee se seco cond nd cel celll (t (the he “C + S” cell in Fig. in Fig. 1b) measures the sum of the compressive 3
D5778 − 12
FIG. 1 Commo Common n Confi Configurat gurations ions for Electri Electric c Frict Friction-C ion-Cone one Penetrometers Penetrometers ( (1 1) Showing: (a) Compression-type Tip and Sleeve Load Cells, (b) Tension-type Sleeve Design, and (c) Subtraction-type Penetrometer
facturers. The need for a specific cone design depends on the design data requirements outlined in the exploration program. 7.1.1.4 7.1.1 .4 Regard Regardless less of penetr penetrometer ometer type, the friction sleeve load cell system must operate in such a way that the system is sensitive to only shear stresses applied to the friction sleeve and not to normal stresses. 7.1.2 Cone— Nominal Nominal dimensions, with manufacturing and operating tolerances, for the cone are shown on Fig. 2. 2. The cone co ne ha hass a di diam amet eter er d = 35 35.7 .7 mm mm,, pr proj ojec ecte ted d ba base se ar area ea 2 Ac = 100 1000 0 mm , + 2 %– %–5 5 % wi with th an ap apex ex an angl glee of 60 60°. °. A cylindrical extension, he, of 5 mm shoul should d be located behind behind the base of the cone to protect the outer edges of the cone base from fr om ex exce cess ssiv ivee we wear ar.. Th Thee 10 cm2 con conee is con consid sidere ered d the refere ref erence nce stan standar dard d for whi which ch res results ults of oth other er pen penetro etromete meters rs with proportionally scaled dimensions can be compared. 7.1.2.1 7.1.2 .1 In certain cases, cases, it may be desira desirable ble to increase the cone diameter in order to add room for sensors or increase ruggedness of the penetrometer. The standard increase is to a base diameter of 43.7 mm which provides a projected cone base area of 1500 mm 2 while maintaining a 60° apex angle. Nominal Nomin al dimens dimensions, ions, with manuf manufacturin acturing g and opera operating ting toler2 ances for the 15 cm cone, are shown in Fig. 2, 2, based on the international guides ( guides (5 5). 7.1.2.2 7.1.2 .2 The cone is made of high strength strength steel of a type and hardness suitable to resist wear due to abrasion by soil. Cone tips which have worn to the operating tolerance shown in Fig. 2 should be replaced. Piezocone tips should be replaced when the tip has worn appreciably (as shown) and the height of the cylindrical extension has reduced considerably (as shown).
forces on both the cone and friction sleeve. The compressive force for ce fro from m the friction friction sle sleeve eve portion portion is com comput puted ed then by subtraction. This cone design is common in industry because of its rugged design. This design forms the basis for minimum performance requirements for electronic penetrometers. 7.1.1 7. 1.1.1 .1 Alter Alternat native ive de desig signs ns ha have ve sep separa arate te an and d no nonndependent load cells separate for tip and sleeve. For instance, in Fig. in Fig. 1a, the cone penetrometer tip produces a compression force on the cone load cell (the “C” cell in Fig. 1a) while the frictio fri ction n slee sleeve ve pro produc duces es a ten tensile sile for force ce on the ind indepe epende ndent nt fric fr ictio tion n sl slee eeve ve lo load ad cel celll (t (the he “S “S”” ce cell) ll).. De Desi sign gnss ar aree als also o available where both the tip and sleeve load cells are independentt and ope den operate rate in com compre pressi ssion on (1). The These se pen penetr etrome ometer ter designs result in a higher degree of accuracy in friction sleeve measurement, however, may be more susceptible to damage under extreme loadin loading g cond conditions. itions. 7.1.1. 7.1 .1.2 2 Typi ypical cal gen genera erall pur purpos posee con conee pen penetro etromete meters rs are manufa man ufactu ctured red to ful fulll sca scale le out output putss (FS (FSO) O) equ equiva ivalen lentt to net loads of 10 to 20 tons. Often, weak soils are the most critical in an investigation program, and in some cases, very accurate friction sleeve data may be required. To gain better resolution, the FSO can be lowered or the independent type penetrometer desig de sign n ca can n be sel select ected ed.. A lo low w FS FSO O su subt btra ract ctio ion n co cone ne may provide more accurate data than a standard FSO independent typee con typ conee dep depend ending ing on suc such h fact factors ors as sys system tem des design ign and thermal compensation. If the FSO is lowered, this may place electrical components at risk if overloaded in stronger soils. Expensive preboring efforts may be required to avoid damage in these cases. The selection of penetrometer type and resolution should consider such factors as practicality, availability, calibration requirements, cost, risk of damage, and preboring requirements. 7.1.1. 7.1 .1.3 3 The user or clie client nt sho should uld select the con conee des design ign requirements by consulting with experienced users or manu-
NOTE 4—In some applications it may be desirable to scale the cone diameter down to a smaller projected area. Cone penetrometers with 5 cm2 projected area find use in the field applications and even smaller sizes (1 cm2) are used in the laboratory for research purposes. These cones should be des design igned ed wit with h dim dimens ension ionss sca scaled led in dir direct ect pro propor portio tion n to sta standa ndard rd
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D5778 − 12
FIG. 2 Manufacturing and Operating Tolerances of Cones ( (5 5)
10-cm2 penetrometers. In thinly layered soils, the diameter affects how accurately the layers may be sensed. Smaller diameter cones may sense thinnerr layers more accurately than larger cones. If there are questi thinne questions ons as to the effect of scaling the penetrometer to either larger or smaller size, results can be compared in the field to the 10-cm2 penetrometer for soils under consideration. This is because the 10-cm2 cone is considered the reference refere nce penetr penetrometer ometer for field testing.
Gap requirements requirements apply to the gaps at either end of the frictio friction n sleeve and to other elements of the penetrometer tip. 7.1.4.1 7.1.4. 1 The gap between between the cyl cylind indrica ricall ext extens ension ion of the cone base and other elements of the penetrometer tip, e c, must not be larger than 5 mm for the friction cone penetrometer. 7.1.4.2 7.1.4. 2 If a sea seall is placed in the gap gap,, it should should be pro proper perly ly designed and manufactured to prevent entry of soil particles into the penetrometer tip. It must have a deformability at least two orders of magnitude greater than the material comprising the loa load d tra transf nsferr erring ing com compon ponents ents of the sen sensin sing g dev devices ices in order to prevent load transfer from the tip to the sleeve.
7.1.3 Friction Sleeve— The The outside diameter of the manufactured factur ed friction sleeve and the operating diameter diameter are equal to the diameter of the base of the cone with a tolerance of +0.35 mm an and d −0 −0.0 .0 mm mm.. Th Thee fr frict ictio ion n sl sleev eevee is ma made de fr from om hi high gh stren str engt gth h st steel eel of a ty type pe an and d ha hard rdne ness ss to re resi sist st we wear ar du duee to abrasion abrasio n by soil. Chrom Chrome-plate e-plated d steel is not recommended recommended due to differing frictional behavior. The surface area of the friction sleeve is 150 cm2 6 2 %, for a 10-cm 2 cone. If the cone base area is increased to 15 cm 2, as provided for in 7.1.2.1, 7.1.2.1, the surf su rfac acee ar area ea of th thee fr fric icti tion on sl slee eeve ve sh shou ould ld be ad adju just sted ed proportionally, with the same length to diameter ratio as the 10-cm2 cone. With the 15-cm2 tip, a sleeve area of 225 cm 2 is similar in scale. 7.1.3.1 7.1.3 .1 The top diameter of the sleeve must must not be smaller than the bottom diameter or significantly lower sleeve resistance will occur. During testing, the top and bottom of the sleeve should be periodically checked for wear with a micrometer. Normally, the top of the sleeve will wear faster than the bottom. 7.1.3. 7.1 .3.2 2 Fri Frictio ction n sle sleeve evess mus mustt be des design igned ed with equal end areas which are exposed to water pressures ( (1 1, 5 5,, 6 6,, 7 7,, 8 8)). This will remove the tendency for unbalanced end forces to act on the sleeve. Sleeve design must be checked in accordance with A1.7 to A1.7 to ensure proper response. 7.1.4 Gap— The The gap (annular space) between the cylindrical exten ex tensio sion n of th thee co cone ne ba base se an and d th thee ot othe herr ele eleme ment ntss of th thee penetrometer tip should be kept to the minimum necessary for operation of the sensing devices and should be designed and constructed in such a way to prevent the entry of soil particles.
7.1.4.3 Filter Element in the Gap— If If a filter element for a piezocone is placed in the gap between cone and sleeve the sum of the height of cylindrical extension, he, plus element thickness filling the gap, ec, can range from 8 to 20 mm (see 7.1.8 for explanation). 7.1.8 7.1.5 Diameter Requirements— The The fri frictio ction n slee sleeve ve sho should uld be situated within 5 to 15 mm behind the base of the cone tip. The annular spaces and seals between the friction sleeve and other oth er por portio tions ns of the pen penetr etrome ometer ter tip mus mustt con confor form m to the samee spe sam specific cificatio ations ns as des descri cribed bed in 7.1.4. 7.1.4. Ch Chan ange gess in th thee diameter of the penetrometer body above the friction sleeve shou sh ould ld be su such ch th that at ti tip p or sl slee eeve ve me meas asur urem emen ents ts ar aree no nott influenced by increases in diameter. International reference test procedures require that the penetrometer body have the same diameter as the cone for the complete length of the penetrometer body (5, 9, 10 10)). 7.1.5.1 7.1.5 .1 For some penetrometer penetrometer designs, designs, it may be desirable to inc increa rease se the diameter diameter of the pen penetr etrome ometer ter body to hou house se additional sensors or reduce friction along push rods. These diameterr changes are accepta diamete acceptable ble if they do not have significant influence on tip and sleeve data. If there is question regarding a specific design with diameter increases, comparison studies 5
D5778 − 12 can be made to a penetrometer with constant diameter. Information on diameters of the complete penetrometer body should be repor reported. ted.
without porewater transducers can be used in soils with minor porewater pressure development, such as clean sands, granular soils, soi ls, as well as soi soils ls and fills wel welll abo above ve the groundwa groundwater ter table. The type 1 with face filter element finds use in fissured geomaterials and materials prone to desaturation, as well as dissipation readings. Numerous design and configuration aspects can affect the measurement of dynamic water pressures. Variables such as the element location, design and volume of port po rts, s, an and d th thee ty type pe an and d de degr gree ee of sa satu tura ratio tion n of th thee flu fluid ids, s, cavitation of the element fluid system and resaturation lag time, dept de pth h an and d sa satu tura ratio tion n of so soil il du duri ring ng tes testin ting g all af affe fect ct th thee dynami dyn amicc por porewa ewater ter pre pressu ssure re mea measur sured ed dur during ing test testing ing and dissipation tests of dynamic pressures ( (2 2, 3 3,, 4 4,, 8 8)). It is beyond the scope of the procedure to address all of these variables. As a minimum, complete information should be reported as to the design des ign,, con configu figurat ration ion,, and the pre prepar paratio ation n of the pie piezoco zocone ne system that is used for the particular sounding.
NOTE 5—The effects caused by diameter changes of the penetrometer on tip and sleeve resistance are dependent on the magnitude of diameter increase and location on the penetrometer body. Most practitioners feel that diameter increases equivalent to addition of a friction reducer with area increases of 15 to 20 % should be restricted to a location at least eight to ten cone diameters behind the friction sleeve.
7.1.6 The axis of the cone, the friction sleeve sleeve (if included), and the body of the penetrometer tip must be coincident. Force Sen Sensin sing g Dev Devices ices— — The 7.1.7 Force The typ typical ical for force ce sen sensin sing g device dev ice is a str strain ain gauge load cell that con contain tainss temp tempera eratur turee compen com pensat sated ed bon bonded ded str strain ain gag gages. es. The con configu figurat ration ion and location of strain gages should be such that measurements are not influenced by possible eccentricity of loading. 7.1.8 Electro piezoc zocone one Electronic nic Piezo Piezocone cone Penet Penetro rometer— meter— A pie penetr pen etrome ometer ter can con contain tain por porous ous filte filterr elem element ent(s) (s),, pre pressu ssure re transducer(s), and fluid filled ports connecting the elements to the transducer to measure pore water pressure. Fig. 3 shows 3 shows the common com mon des design ign typ types es use used d in pra practic cticee inc includ luding ing:: 1010-cm cm2 friction-type, type 1 and type 2 piezocone, and 15-cm 2 size. The standard penetrometer should be the type 2 piezocone with filter located at the shoulder (both 10-cm 2 and 15-cm 2) to allow correction of tip resistances. The electric friction penetrometer
7.1.8.1 7.1.8 .1 Measu Measurement rement of hydr hydrostatic ostatic water pressures during pauses in testing are more straig pauses straightfor htforward. ward. The presence of air entrained entrai ned in the system only affects affects dynamic response. In high permeability soils (that is, clean sands), hydrostatic pressures will equalize within seconds or minutes. In low permeability materials such as high plasticity clays, equalization can take many hours. If the goal of the exploration program is only to
FIG. 3 Penetrometer Design Configurations: (a) Electronic Friction-type, (b) Type 1 Piezocone, (c) Standard 10-cm 2 Type 2 Piezocone, and (d) 15-cm2 Type 2 Version (7 (7)
6
D5778 − 12 acquire hydrostatic pressures in sands, some of the preparation procedures proced ures for dyna dynamic mic pressu pressure re measur measuring ing can be relaxe relaxed, d, such as deairing fluids. 7.1.8.2 7.1.8 .2 The porewater pressure measurement measurement locatio locations ns of the porous element element are limited to the face or tip of the cone, u 1, directl dir ectly y beh behind ind the cyl cylind indric rical al ext extens ension ion of the bas basee of the cone, u 2, or behind the sleeve, u3. Some penetrometers used for research purposes may have multiple measurement locations. 7.1.8.3 7.1.8 .3 There are several advantages advantages to locatin locating g the porou porouss element immediately behind the tip of the cone in location u 2, primarily the required correction of measured q c to total tip stress, qt, as detailed extensively ( extensively (4-8 the element is less less 4-8)). Also, the subject to damage and abrasion, as well as fewer compressibility effects ( effects (4 4, 8 8)). Elements located in the u 2 location may be subject to cavitation at shallow depths in dense sands because the zone behind the height of cylindrical extension is a zone of dilatio dila tion n in dra drained ined soils. Sim Similar ilar response response can occ occur ur in stif stiff f fissured clays and crusts ( (4 4). Porewater pressure measurements obtained at the u1 face location are more effective for compressibility determinations and layer detection, particularly in fissured soils, but are more subject to wear (3, 11 11)). At the u2 location, a minimum 2-mm cylindrical extension of the cone tip (he) should be maintained for protection of the cone. Typical filter element thickness at all locations in the horizontal plane ranges from 5 to 10 mm. 7.1.8.4 7.1.8 .4 The miniatu miniature re diaph diaphragmragm-type type electro electronic nic pressu pressure re transducer is normally housed near the tip of the cone. For dynamic pressure measurements, the filter and ports are filled with dea deaire ired d flui fluid d to mea measur suree dyn dynamic amic por porewa ewater ter pre pressu ssure re respon res ponse. se. The vol volume ume of con connec nectin ting g por ports ts to the tran transdu sducer cer should be minimized to facilitate dynamic pressure response. These The se ele electr ctron onic ic tra transd nsduce ucers rs are no norma rmally lly ver very y rel reliab iable, le, accurate, and linear in response. The transducer shall have a precision precisi on of at least 614 kPa ( 62 psi). The porewater pressure transducer must meet requirements given in 10.2 10.2.. 7.1.8.5 Element— The The element is a fine porous filter made from plastic, sintered steel or bronze, or cerami ceramic. c. Typical Typical pore size is between 20 to 200 microns ( (8 8, 11 11)). Different materials have different advantages. Smearing of metallic element openings by hard soil grains may reduce dynamic response of the system, sys tem, thus nor normall mally y not used for face elem element entss but best suited for shoulder filter positions. Ceramic elements are very brittle and may crack when loaded, but perform well on the cone face as they reduce compressibility concerns. Polypropylene plastic elements are most commonly used in practice, particu par ticular larly ly at the sho should ulder er.. Plas Plastic tic filt filters ers (as hig high-d h-dens ensity ity polyethylen polyet hylene, e, HDPE, or highhigh-densit density y polyp polypropy ropylene, lene, HDPP) may be ina inappr ppropr opriate iate for env enviro ironme nmenta ntall typ typee CPT CPTss whe where re contaminant detection is sought. Typically, the filter element is wedged at the tip or midface ( u1) location, or located at the should sho ulder er in the gap imm immedia ediately tely above the con conee ext extens ension ion (designated u2) location. At these locations, it is important to design des ign the pen penetr etrome ometer ter suc such h tha thatt com compre pressi ssion on of the filt filter er elements is minimized. Fluids for Satur Saturation ation— — Glycerine, 7.1.8.6 Fluids Glycerine, or alterna alternatively tively silico sil icone ne oi oil, l, is mo most st of often ten us used ed fo forr de deai airin ring g el elem emen ents ts fo forr dynamic response. These stiff viscous oils have less tendency to cav cavita itate te,, al alth thou ough gh cav cavita itati tion on ma may y be co cont ntro rolle lled d by th thee
effective pore size of the element mounting surfaces. Water can be used for the fluid if the entire sounding will be submerged, or if dynamic response is not important. The fluids are deaired using procedures described in 11.2 11.2.. 7.2 Measuring System— The The signals from the penetrometer transducers are to be displayed at the surface during testing as a continuously updated plot against depth. The data are also to be record recorded ed electro electronically nically for subse subsequent quent processing. processing. Electronic recording recording shall be digita digitall and use at least twelve bit (one partt in 409 par 4096) 6) res resolu olution tion in the ana analog log to dig digital ital con conver versio sion, n, although 16-bit resolution and higher may be preferable in very soft ground. Either magnetic (disk or tape) or optical (disk) nonno n-vo volat latile ile st stor orag agee ma may y be us used ed.. In an analo alog g sy syste stems ms,, th thee tempera temp eratur turee stab stabilit ility y and accu accurac racy y of the A-t A-to-D o-D con conver verter ter shall sha ll be suc such h that the ove overal ralll con cone-tr e-trans ansmis missio sion-r n-reco ecordi rding ng system complies with calibration requirements set forth in the annex. 7.2.1 7.2 .1 Use of ana analog log systems systems is acce accepta ptable ble but the system resolution may be lower than requirements in the annex and Section 10 10.. Use of an an analo alog g re reco cord rder er as a su supp pple lemen mentt to digital system is advantageous because it can provide system backup. NOTE 6—Depen 6—Dependin ding g upo upon n the equ equipm ipment ent,, dat dataa sto stored red dig digital itally ly on magnetic drives, tapes, floppy disks, or other media are often used. The dataa file dat filess sho should uld inc includ ludee pro projec ject, t, loc locatio ation, n, ope operat rator or,, and dat dataa for format mat information (for example, channel, units, corrected or uncorrected, etc.) so that the data can be understood when reading the file with a text editor.
Push Rod Rods— s— Steel 7.3 Push S teel ro rods ds ar aree re requ quire ired d ha havi ving ng a cr cros osss sectional section al area adequate to sustai sustain, n, without buckling, the thrus thrustt required to advance the penetrometer tip. For penetrometers using electrical cables, the cable is prestrung through the rods prior to testing. Push rods are supplied in 1-meter lengths. The push rods must be secured together to bear against each other at the joints and form a rigid-jointed string of push rods. The deviation of push rod alignment from a straight axis should be held he ld to a mi mini nimu mum, m, es espe peci ciall ally y in th thee pu push sh ro rods ds ne near ar th thee penetrometer tip, to avoid excessive directional penetrometer drift. Generally, when a 1-m long push rod is subjected to a permanent circular bending resulting in 1 to 2 mm of center axis rod shortening, the push rod should be discarded. This corr co rres espo pond ndss to a ho hori rizo zont ntal al de defle flecti ction on of 2 to 3 mm at th thee center cen ter of ben bendin ding. g. The loc locatio ations ns of push rod rodss in the string string should be varied periodically to avoid permanent curvature. 7.3.1 7.3 .1 For the 10-cm 10-cm 2 penetr penetrometer ometer,, stand standard ard 20-m 20-metric etric ton high hi gh te tens nsile ile st stre reng ngth th st stee eell pu push sh ro rods ds ar aree 36 36-m -mm m ou outsi tside de diameter, 16-mm inside diameter, and have a mass per unit length of 6.65 kg/m. For 15-cm 2 penetrometers, the test may be pushed with 44.5-mm outside diameter rods or with standard rods used for the 10-cm 2 penetrometer.
7.4 Friction Reducer— Friction Friction reducers are normally used on the push rods to reduce rod friction. If a friction reducer is used, it should be located on the push rods no closer than 0.5 m behind the base of the cone. Friction reducers, that increase push rod outside diameter by approximately 25 %, are typically used for 10-cm 2 cones. If a 15-cm 2 penetr penetrometer ometer is advan advanced ced with wi th 36 36-m -mm m pu push sh ro rods ds th ther eree ma may y be no ne need ed fo forr fr frict ictio ion n reducers since the penetrometer itself will open a larger hole. 7
D5778 − 12 The type, size, amount, and location of friction reducer(s) used during testing must be reported.
9.1.2 The application application of thrust thrust in excess of rated capacity of the equipment can result in damage to equipment (see Section 6). 9.1.3 9.1 .3 A cone sou soundi nding ng mus mustt not be per perfor formed med any clo closer ser than 25 borehole diameters from any existing unbackfilled or uncased bore hole. 9.1.4 When performing cone penetration testing in prebored holes, an estimate of the depth below the prebored depth which is di dist stur urbe bed d by dr drill illin ing, g, sh shou ould ld be mad madee an and d pe pene netr trat atio ion n resistance data obtained in this zone should be noted. Usually, this depth of disturbance is assumed to be equal to at least three borehole diameters. 9.1.5 9.1 .5 Sig Signifi nifican cantt ben bendin ding g of the pus push h rod rodss can infl influen uence ce penetration resistance data. The use of a tubular rod guide is recommended at the base of the thrust machine and also in prebored holes to help prevent push rod bending. 9.1.6 Push rods not meeting requireme requirements nts of 7.3 of 7.3 may result in excessive directional penetrometer drift and possibly unreliable penetr penetration ation resistance values values.. 9.1.7 Passin Passing g through or alongside obstructions obstructions may deflect the penetrometer and induce directional drift. Note any indications of encountering such obstructions, such as gravels, and be aler alertt for pos possib sible le sub subseq sequen uentt imp improp roper er pen penetro etromete meterr tip operation. 9.1.8 If the proper rate rate of advance of the penetrometer penetrometer is not maintain main tained ed for the ent entire ire str stroke oke thr throug ough h the mea measur suremen ementt interval, penetration resistance data will be erroneous.
7.5 Thrust Machine and Reaction— The The thrust machine will provide a contin provide continuous uous stroke, preferably preferably over a distan distance ce greater than 1 m. The thrust machine should be capable of adjusting push direction through the use of a leveling system such that push pus h init initiate iatess in a ver vertica ticall ori orient entatio ation. n. The mach machine ine mus mustt adva ad vanc ncee th thee pe pene netr trom omete eterr tip an and d pu push sh ro rods ds at a sm smoo ooth th,, constant rate (see 12.1.2) 12.1.2) while the magnitude of thrust can fluctuate. The thrust machine must be anchored or ballasted, or both, so that it provides the necessary reaction for the penetrometer and does not move relative to the soil surface during thrust. NOTE 7—Cone penetration soundings usually require thrust capabilities ranging from 100 to 200 kN (11 to 22 tons) for full capacity. High mass ballasted vehicles can cause soil surface deformations which may affect penetrometer resistance(s) measured in near surface layers. Anchored or ballas bal lasted ted veh vehicl icles, es, or bot both, h, may ind induce uce cha change ngess in gro ground und sur surfac facee reference level. If these conditions are evident, they should be noted in reports.
7.6 Other Sensing Devices— Other Other sensing devices can be include inclu ded d in th thee pe pene netr trom omete eterr bo body dy to pr prov ovid idee ad addi diti tion onal al information during the sounding. These instruments are normally mal ly re read ad at th thee sa same me co cont ntin inuo uous us ra rate te as ti tip, p, sl slee eeve ve,, an and d porewater pressure sensors, or alternatively, during pauses in thee pu th push sh (o (oft ften en at 11-m m ro rod d br brea eaks ks). ). Typ ypica icall sen senso sors rs ar aree inclinometer inclino meter,, temper temperature, ature, resistivity (or its recipr reciprocal, ocal, electrical conductivity), or seismic sensors, such as geophones that can be used to obtain downhole shear wave velocity. These senso sen sors rs sh shou ould ld be ca calib libra rated ted if th their eir us usee is cr criti itica call to th thee investi inv estigat gation ion pro progra gram. m. The use of an incl inclino inomete meterr is hig highly hly recommended since it will provide information on potentially damaging situations during the sounding process. An inclinometer can pro provid videe a use useful ful depth reliabilit reliability y che check ck bec becaus ausee it provid pro vides es inf inform ormatio ation n on ver vertica ticality lity.. The con configu figurati ration on and methods of operating such sensors should be reported.
9.2 Technical Precautions—Electronic Friction Cone Penetrometer: 9.2. 9. 2.1 1 Fa Failu ilure re of OO-ri ring ng sea seals ls ca can n re resu sult lt in da dama mage ge to or inaccurate inaccu rate readin readings gs from electronic transd transducers ucers.. The O-rin O-ring g seals should be inspected regularly, after each sounding, for overall overa ll condi condition, tion, cleanli cleanliness ness and waterti watertightne ghtness. ss. 9.2.2 Soil ingress between different different elements of a penetrometer tip can result in unreliable data. Specifically, soil ingress will detrimentally affect sleeve resistance data. Seals should be inspected inspec ted after each sound sounding, ing, maintained regularly, regularly, and replaced when necessary. If very accurate sleeve resistance data is req requir uired, ed, it is rec recomm ommend ended ed to clea clean n all seals aft after er eac each h sounding. 9.2.3 Electro Electronic nic cone penetrometer penetrometer tips should be temperature compensated. If extreme temperatures outside of the range established establi shed in in A1.3.3 A1.3.3 are to be encountered, the penetrometer shou sh ould ld be ch chec ecke ked d fo forr th thee re requ quir ired ed tem tempe pera ratu ture re ra rang ngee to establi esta blish sh they can meet the cali calibra bration tion req requir uireme ements nts.. Als Also, o, harsh environments environments may severe severely ly af affect fect the data acquisition system of power supplies, notebook or field computers, and other electronics. 9.2.4 9.2 .4 If the shift in bas baselin elinee rea readin ding g afte afterr ext extrac racting ting the penetrometer tip from the soil is so large that the conditions of accuracy as defined in 10.1.2.1 in 10.1.2.1 are are no longer met, penetration resi re sista stanc ncee da data ta sh shou ould ld be no noted ted as un unre relia liabl ble. e. If ba base selin linee readin rea dings gs do not con confor form m to allo allowab wable le limi limits ts esta establi blishe shed d by accuracy requirements in 10.1.2.1 10.1.2.1,, the penetrometer tip must be repaired, and recalibrated or replaced. 9.2.5 Electronic friction cone penetrometers having unequal end en d ar area eass on th their eir fr fric ictio tion n sl sleev eeves es ca can n yi yield eld er erro rone neou ouss f s
8. Reag Reagents ents and Materials Materials 8.1 O-Ring Compound— A petroleum or silicon compound for facilitating seals with O-rings. Use of silicon compounds may impede repair of strain gages if the strain gauge surface is exposed to the compound. 8.2 Glycerine, or CHOH( CHOH(CH CH2OH)2, fo forr us usee in po pore rewa water ter pressu pre ssure re mea measur suremen ementt sys systems tems.. App Approx roximat imately ely 95 % pur puree glycerine can be procured from most drug stores. Silicone Oil (or flui fluid), d), for use in por 8.3 Silicone porewa ewater ter pre pressu ssure re measure meas uremen mentt sys systems tems.. Thi Thiss mate materia riall is ava availab ilable le in var varyin ying g viscosities ranging from 1400 to 10 000 CP. NOTE 8—Detailed 8—Detailed comparisons comparisons and discu discussion ssionss on the use of these (8 8, 11 11)). fluids can be found elsewhere (
9. Haza Hazards rds 9.1 Technical Precautions—General: 9.1.1 9.1 .1 Use of pen penetr etrome ometer ter com compon ponents ents that do not meet required requir ed tolerances or show visible signs of nonnon-symmet symmetric ric wear can result in erroneous penetration resistance data. 8
D5778 − 12 readings because of dynamic porewater pressures acting unevenly on the sleeve ( sleeve (1 1, 5 5,, 6 6,, 8 8)). Friction sleeve design should be ch check ecked ed in ac acco cord rdan ance ce wi with th A1.7 to ens ensure ure bal balanc anced ed response. The response is also dependent on location of water seals. If O-ring water seals are damaged during testing, and sleeve data appear affected, the sounding data should be noted as unreliable and the seals should be repaired.
baseline. The change in initial and final baseline values should not exceed 2 % FSO for the con conee tip tip,, slee sleeve, ve, and pre pressu ssure re transducer. 10.1.2 10. 1.2.1 .1 Main Maintain tain a con contin tinuou uouss rec record ord of ini initial tial and fina finall baselin bas elines es dur during ing pro produc duction tion test testing ing.. Aft After er each sou soundi nding, ng, compare the final baseline to the initial baseline for agreement within the tolerances noted above. In some cases during heavy produc pro ductio tion n test testing ing whe where re the con conee is not dis disass assemb embled led and cleaned after each sounding, the initial baseline for the next soun so undi ding ng ca can n se serv rvee as th thee fin final al ba basel selin inee to th thee pr prev evio ious us sounding as long as agreement is within allowable limits. 10.1.2.2 10.1. 2.2 If the post sounding sounding baseline shift exceeds above criteria, inspect the cone for damage by inspecting the tip and checking to see that the sleeve can be rotated by hand. If there is apparent damage, replace parts as required. Clean the cone and allow temper temperatures atures to equaliz equalizee to preso presoundin unding g condit conditions, ions, and obtain a new baseline. If this value agrees with the initial baselin bas elinee with within in the abo above ve cri criter teria, ia, a loa load d ran range ge cali calibra bratio tion n check is not required. If the pre and post baselines are still not within the above criteria then it is likely that the shift was caused by an obstacle or obstruction and linearity should be checked with a load range calibration. 10.1.2.3 10.1. 2.3 If the baseline shift still exceeds exceeds the above criteria, perform a load range calibration as described in 10.1.2.1 10.1.2.1.. If the cone load cell baseline shift exceeds 2 % FSO, the cone is likely lik ely da dama mage ged d an and d wi will ll no nott me meet et lo load ad ra rang ngee cr crite iteri riaa in 10.1.2.2.. Sleeve load cell baseline shifts for subtraction-type 10.1.2.2 penetrometers usually can exceed 2 % FSO and still meet load range criteria. 10.1.2.4 10.1. 2.4 Report data for the sounding where unacceptable unacceptable baseline shift occurs as unreliable. In some cases it may be obvious where the damage occurred and data prior to that point may ma y be co cons nsid ider ered ed re relia liabl ble. e. Th Thee lo loca catio tion n wh wher eree ob obvi viou ouss damage occurred should be clearly noted in reports. 10.1.3 Penetrometer Wear and Usage 10.1 10 .1.3 .3.1 .1 For For pe pene netr trom omet eter erss us used ed re regu gula larl rly y du duri ring ng production, periodic load range checks should be performed. The inspection period can be based on production footage such as on once ce ev ever ery y lin lineal eal 30 3000 00 m (a (app ppro rox. x. 104 lin linear ear fee feet) t) of soundings. If field load range equipment is not available, the penetrometer may be checked in the laboratory at the end of a project. 10.1.3 10. 1.3.2 .2 For pen penetr etrome ometers ters tha thatt are use used d inf infreq requen uently tly,, a periodic check may be based on time period, such as once every year. If a penetrometer has not been used for a long period of time, checking it before use is advisable. 10.1 10 .1.3 .3.3 .3 For pr proj oject ectss re requ quir irin ing g a hi high gh lev level el of qu qual ality ity assurance, it may be required to do load range checks before and after the project. 10.1.3.4 10.1. 3.4 Load range calibrations calibrations are requi required red if the initial and final baselines for a sounding do not meet requirements given in 10.1.2.1 10.1.2.1.. 10.1.3.5 10.1. 3.5 Record Recordss docum documenting enting the history of an individual individual penetrometer should be maintained for evaluation of performance.
Piezocone Penetr Penetromete ometer— r— The 9.3 Piezocone T he ele electr ctroni onicc pie piezoc zocone one penetrometer tip measures pore water pressures on the exterior of the penetrometer tip by transferring the pressure through a de-aired fluid system to a pressure transducer in the interior of the tip. For proper dynamic response, the measurement system (consisting of fluid ports and porous element) must be completely plet ely satu saturate rated d pri prior or to test testing ing.. Ent Entrai rained ned air mus mustt be removed mov ed fro from m the flui fluid-fi d-filled lled sys system tem or por porewa ewater ter pre pressu ssure re fluctuation during penetrometer tip advancement will be incorrect due to response lag from compression of air bubbles (see 11.2,, 12.3.2, 11.2 12.3.2, and 12.3.3) 12.3.3). Fo Forr so soun undi ding ngss wh wher eree dy dyna nami micc response is important, the prepared filter elements should be replaced after every sounding.
10. Calibration and Standardizatio Standardization n 10.1 Electronic Friction Cone Penetrometers: 10.1.1 The req 10.1.1 requir uireme ements nts for new newly ly man manufa ufactu ctured red or repaired cone penetrometers are of importance. Newly manufacture tu red d or re repa pair ired ed el elect ectro roni nicc co cone ne pe pene netr trom omete eters rs ar aree to be checke che cked d to mee meett the min minimu imum m cal calibr ibratio ation n req requir uireme ements nts described scr ibed in the ann annex. ex. These cali calibra bration tionss inc includ ludee loa load d test tests, s, thermal tests, and mechanical tests for effects of imbalanced hydrostatic hydro static force forces. s. Calibra Calibration tion proce procedures dures and requi requirement rementss given in the annex are for subtraction-type cone penetrometers. Calibration requirements for independent-type cone penetrometers should equal or exceed those requirements. The calibration tio n re reco cord rdss mu must st be ce cert rtifie ified d as co corr rrec ectt by a re regi giste stere red d prof pr ofess ession ional al eng engine ineer er or oth other er re resp spon onsib sible le eng engin ineer eer wi with th knowle kno wledge dge and exp experi erienc encee in mate material rialss test testing ing for qua quality lity assuran assu rance. ce. Applied Applied for forces ces or mas masses ses mus mustt be tra traceab ceable le to calibration standard forces or masses retained by the National Institute Institu te of Stand Standards ards and Technology Technology (NIST), formerly the National Bureau of Standards. For description of calibration terms and methods for calibrating, refer to the annex. 10.1.2 Baseline Readin Baseline or zero-load readings Readings— gs— Baseline for both con conee and friction friction slee sleeve ve load cells and porewater porewater pres pr essu sure re tr tran ansd sduc ucer erss mu must st be tak taken en be befo fore re an and d af after ter ea each ch sounding. The baseline reading is a reliable indicator of output stability stabilit y, temper temperatureature-induc induced ed appar apparent ent load, soil ingres ingress, s, internal tern al fri frictio ction, n, thr thresh eshold old sen sensiti sitivit vity y, and unk unknow nown n loa loadin ding g during dur ing zer zero o set setting ting.. Take the ini initial tial bas baselin elinee rea readin ding g aft after er warming warmin g electri electrical cal circuit circuitss accord according ing to the manuf manufacture acturer’s r’s instructions, generally for 15 to 30 min, and in a temperature environment as close as possible to that of the material to be sounded. If temperature is of concern, immerse the penetrometer tip in a bucket of fresh tap water, or insert the penetrometer tip in the ground while electrically warming circuits to stabilize its temperature and then extracted for rapid determination of initial init ial bas baselin eline. e. After a sou soundi nding ng is com comple pleted ted,, tak takee a fina finall
Porewater ter Pres Pressure sure Tr Transdu ansducer— cer— Calibrat 10.2 Porewa C alibratee new newly ly manufa man ufactu ctured red or rep repair aired ed tran transdu sducer cerss in acco accorda rdance nce wit with h requirements in the annex. During production, the transducer 9
D5778 − 12 should be cali should calibra brated ted at reg regula ularly rly sch schedu eduled led int interv ervals als and whenever linear performance is suspect. The reference gauge can be a Bourdon tube pressure gauge, or electronic pressure transducer that is calibrated annually to NIST traceable loading device (dead weight testing apparatus).
11.2.3 Ele 11.2.3 Elemen ments ts can be pre prepar pared ed in wate waterr by boi boilin ling g the elements while submerged in water for at least 4 h, although damage may result from prolongued exposure in this approach (4). Other er Sui Suitab table le Mea Means— ns— Report 11.2.4 Oth Report oth other er tech techniq niques, ues, such as commercially-purchased pre-saturated filter elements that are available, or grease-filled slot (1, 7). 11.2.5 Storage— Store Store prepared elements submerged in the prep pr epar ared ed flu fluid id un until til re read ady y fo forr us use. e. Fil Filll th thee co cont ntain ainer erss an and d evacuate evacua te durin during g storag storage. e. Allowable storage length depen depends ds on thee flu th fluid id.. If el eleme ement ntss ar aree pr prep epar ared ed in wa water ter th they ey mu must st be deaired again one day after containers are opened and exposed to air. Elements stored in glycerine or silicone may be stored for longer periods, up to sever several al month months, s, after storage containers have been exposed to air.
10.2.1 Prior to testing, baseline 10.2.1 baseline values or initial zeroing zeroing of the transducer is performed on the porewater pressure transducer at ambient air pressures at the surface. Maintain records as to the baseline values values for the transd transducer ucer in similar fashion to those for tip and sleeve resistance. If significant changes in baseline values occur, normally 1 to 2 % FSO, perform load rang ra ngee tes tests ts to ch check eck fo forr po poss ssib ible le da damag magee an and d no nonl nlin inear ear response. Calibratio tions ns of Oth Other er Sen Sensin sing g Dev Devices ices— — Calibration 10.3 Calibra Calibration data for other sensors in the penetrometer body may require calibra cali bration tionss usi using ng pro proced cedure uress sim similar ilar to tho those se giv given en in the annex for load cells and pressure transducers. The need for calibra cali bration tion dep depend endss on the req requir uireme ements nts of the ind individ ividual ual investigation investi gation program. For noncr noncritical itical prog programs, rams, the occur occur-rence ren ce of rea reason sonabl ablee rea readin dings gs may be suf suffficie icient. nt. In crit critical ical programs, it may be necessary to load the sensor through the range of interest with reference standards to ensure accurate readings.
12. Procedur Proceduree
11.2.1 Field or laboratory tests can be performed performed to evaluate assembled system response, if desired. Place the cone tip and element in a press pressurized urized chamber chamber and subje subject ct to rapid pressure pressure change cha nge.. Com Compar paree the res respon ponse se of the system to the applied applied pressure changes and if responses match, the system is properly prepared.
12.1 General Requirements: 12.1.1 12.1. 1 Prior to beginning a sounding, perform perform site surve surveys ys to ensure hazards such as overhead and underground utilities will not be encountered. Position the thrust machine over the location of the sounding, and lower leveling jacks to raise the machin mac hinee mas masss of offf the sus suspen pensio sion n sys system. tem. Set the hyd hydrau raulic lic rams of the penetrometer thrust system to as near vertical as possib pos sible. le. The axi axiss of the push rods must coi coinci ncide de wit with h the thrust direction. 12.1 12 .1.2 .2 Set th thee hy hydr drau aulic lic ra ram m fe feed ed ra rate te to ad adva vanc ncee th thee penetrometer at a rate of 20 6 5 mm/s for all electronic cone penetrometers. This rate must be maintained during the entire stroke str oke dur during ing dow downwa nward rd adv advanc ancee of the rod rodss whi while le tak taking ing readings. 12.1.3 12. 1.3 Check Check pus push h rod rodss for str straigh aightne tness ss and per perman manent ent bendin ben ding g (Se (Seee Sect Section ion 7.3 7.3). ). Pu Push sh ro rods ds ar aree ass assem embl bled ed an and d tightened by hand, but care must be taken and threads may need cleaning to ensure that the shoulders are tightly butted to preven pre ventt dam damage age to the push rod rods. s. For electroni electronicc con conee pen pen-etrometers using cables, the cable is prestrung through the push rods. Add friction reducer to the string of push rods as required, required, usually the first push rod behind the penetrometer tip and other rods as required. 12.1.4 12.1. 4 Inspe Inspect ct penetr penetrometer ometer tips before and after soundings soundings for damage, soil ingress, and wear. In very soft and sensitive soils where accurate sleeve data is required, dismantle electronic cone penetrometer tips and friction sleeves after each sounding to clean and lubricate as required. If damage is found after af ter a so soun undi ding ng,, no note te an and d re reco cord rd th this is in info form rmati ation on on th thee sounding data record or report.
11.2.2 11 .2.2 Place elements elements in a pure glycerine glycerine or silicone oil bath under a vacuum of at least 90 % of one atmosphere (–90 kPa). Maintain vacuum until air bubble generation is reduced to a minimum. Application of ultrasonic vibration and low heat (T < 50°C) will assist in removal of air. Generally with use of combin com bined ed vac vacuum uum,, ultr ultraso asonic nic vib vibrat ration ion,, and low hea heat, t, filt filter er elements can be deaired in about 4 h, although it is best to allow for 24 h to ensur ensuree best performance. performance. Results will depend upon up on the vi visco scosit sity y of th thee flu fluid id an and d po pore re siz sizee of th thee fil filter ter element.
12.2 Friction Cone Penetrometers: 12.2.1 12.2. 1 Power up the penetrometer penetrometer tip and data acquisition acquisition system sys tem acco accordi rding ng to the man manufa ufactu cturer rer’s ’s reco recomme mmenda ndatio tions, ns, typically 15 to 30 min, prior to use. 12.2.2 12.2. 2 Obtain an initial baseline reading for the penetrompenetrometer in an unloaded unloaded conditio condition n at a temp tempera eratur turee as clo close se as possible to ground conditions. Obtain baseline readings with the penetrometer tip hanging freely in air or in water, out of direct sunlight. Compare baseline readings with the previous baselin bas elinee rea readin ding g for the req requir uireme ements nts giv given en in 10.1.2.1. 10.1.2.1. If
11. Conditioning 11.1 Power electronic 11.1 electronic cone penetrometer penetrometer and data acquisition systems for a minimum time period to stabilize electric circuit circ uitss bef before ore per perfor formin ming g sou soundi ndings ngs.. Pow Power er the sys system tem to manufacturer’s recommendations prior to obtaining reference baselines. For most electronic systems this time period is 15 to 30 min. 11.2 Electro 11.2 Electronic nic piezoc piezocone one penetr penetrometer ometer soundings require special spe cial pre prepar paratio ation n of the tran transmit smittin ting g flui fluid d and por porous ous elements such that entrained air is removed from the system. For soundings where dynamic response is important, replace the prep pr epar ared ed fil filter ter ele eleme ment ntss an and d th thee po port rtss flu flush shed ed af after ter ev ever ery y sounding. Some of the techniques discussed below have been success suc cessful ful for pre prepar paratio ation n of ele elemen ments. ts. Reg Regard ardles lesss of the techniques used, report the equipment and methods.
10
D5778 − 12 thermal stability needs to be assured, immerse the penetrometer tip in water at temperature close to ground; or perform an initial short penetration test hole, stop penetration and allow the penetrometer tip to reach soil temperature, and withdraw the penetrometer. 12.2.3 12.2. 3 Measu Measure re the depth at which readings readings were taken with an accuracy of at least 6100 mm from the ground surface. 12.2.4 12. 2.4 Det Determ ermine ine the con conee res resista istance nce and fri frictio ction n sle sleeve eve resista res istance nce,, con continu tinuous ously ly wit with h dep depth, th, and rec record ord the dat dataa at intervals of depth not exceeding 50 mm. 12.2.5 12. 2.5 Dur During ing the pro progre gress ss of sou soundi nding, ng, mon monito itorr tip and sleeve forces continuously for signs of proper operations. It is helpful help ful to mon monitor itor other indicator indicatorss suc such h as ram pre pressu ssure re or inclina incl ination tion to ens ensure ure that dam damage age may not occur if hig highly hly resistant layers or obstructions are encountered. Inclination is a particularly useful indicator of imminent danger to the system (see 12.4 (see 12.4). ). 12.2.6 12. 2.6 At the end of a sou soundi nding, ng, extract extract the penetrome penetrometer ter tip, obtain a final set of baseline readings with the penetrometer tip hanging freely in air or in water, and check them against the initi in itial al ba base selin line. e. Rec Recor ord d in initi itial al an and d fin final al ba base selin lines es on all documents related to the sounding.
12.3.5 Follow procedure 12.3.5 proceduress similar to electric friction friction cone in 12.2.4 12. 2.4 – 12. 12.2.6 2.6 with with the add additio ition n of rec record ording ing por porewa ewater ter pressure readings. 12.3.6 Dissipation Tests— If If dissipation tests are to be conducted during progress of the sounding, penetration is temporarily stopped at the location of interest. If porewater pressures are measured at the u 2 or u 3 locations locations,, it is common practice to release the force on the push rods. If porewater pressures are measured at the midface location u 1, maintain the force on the push pus h rod rods. s. Reco Record rd por porewa ewater ter pre pressu ssure re ver versus sus tim timee dur during ing conduct of the dissipation test. Monitor pressures until equilibrium porewater pressure is reached or 50 % of the initial excess porewater pressure has dissipated. In fine grained soils of very low conductivity, very long times may be required to reach the 50 % dissipation. Depending on the requirements of the program, and any concern of friction buildup on the push rods, dissipation testing may be terminated prior to reaching thee 50 % le th leve vel. l. Rep Repor ortt di diss ssip ipat atio ion n tes testt da data ta as a re reco cord rd of porewater pressure versus time, or more commonly, u versus logarithm of time. Hydrostaticc Por Porewater ewater Condit Condition— ion— If 12.3.7 Hydrostati If ful fulll dis dissip sipaations tio ns ar aree ca carr rrie ied d ou out, t, th then en th thee po pore rewa wate terr tr tran ansd sduc ucer er wi will ll eventually record the hydrostatic condition, thus providing an evaluation of the position of the groundwater table or phreatic surface.
12.3 Electronic Piezocone Penetrometers: 12.3.1 12.3. 1 Power up the penetrometer penetrometer tip and data acquisition acquisition system sys tem acco accordi rding ng to the man manufa ufactu cturer rer’s ’s rec recomm ommend endatio ations, ns, typically 15 to 30 min, prior to use. 12.3.2 12.3. 2 Assemb Assemble le the piezo elements with all fluid chambers submerged in the de-aired medium used to prepare the elements. men ts. Fl Flus ush h al alll co confi nfine ned d ar area eass wi with th flu fluid id to re remo move ve air bubb bu bble les. s. Tig ight hten en th thee co cone ne tip to ef effe fect ctiv ively ely se seal al th thee fla flatt surfaces. For water fluid systems, protect the assembled system from fro m eva evapor poratio ation n by enc enclos losing ing the por porous ous elem element ent ins inside ide a fluid-filled plastic bag or cap sealed to the penetrometer tip. 12.3.3 12.3. 3 If unsaturated unsaturated soil is first penetrated and it is desired to obtain accurate dynamic porewater pressure response once below the ground water, it may be necessary to prebore or soun so und d a pi pilo lott ho hole le to th thee wa water ter table. table. In ma many ny ca case ses, s, th thee piezoc pie zocone one flui fluid d sys system tem may cav cavitat itatee dur during ing pen penetr etratio ation n through unsaturated soil or in dilating sand layers below the water table and this can adversely affect dynamic response. As the cone is advanced deeper, the saturation levels may recover as air bubbles are driven back into solution according to Boyles Law. Evaluation of proper interpretation of dynamic response requires experience (4, 5, 8, 12 12)). Pre-punching or pre-boring with wit h a tw twoo-lev level el ph phas asee ap appr proa oach ch to so soun undi ding ngss ma may y he help lp alleviate desaturation problems. 12.3.4 12.3. 4 Record baseline baseline readin readings gs with the penetrometer penetrometer tip hang ha ngin ing g fr freel eely y in air air,, or in wa water ter,, ou outt of di dire rect ct su sunl nlig ight ht.. Compare baseline readings with reference baseline readings for requirements requir ements given in 10.1.2.1 and 10.2. 10.2. A baseline for the porewater porew ater pressu pressure re trans transducer ducer is obtain obtained ed immedia immediately tely after assembl asse mbly y to avo avoid id eva evapor poratio ation n ef effec fects. ts. If eva evapor poratio ation n is a problem, temporarily immerse the penetrometer in a bucket of water wa ter un unti till re read ady y fo forr ba basel selin ine. e. Do no nott ob obta tain in tr tran ansd sduc ucer er baselines with protective caps or covers in place as these may induce ind uce pre pressu ssure re in the sys system. tem. Note the pre pressu ssure re fro from m the pressure transducer to see if it is a reasonable value for the equipment and assembly technique used.
12.4 Pene Penetro trometer meter Oper Operatio ation n and Data Inte Interpr rpretati etationonGuidelines: 12.4.1 Directional Drift of Penetrometer: 12.4.1 12. 4.1.1 .1 The pen penetro etromete meterr may dri drift ft dir directi ectiona onally lly fro from m vertical alignment. Large deviations in inclination can create nonuniform loading and result in unreliable penetration resistance data. Reduce drift by accurately setting thrust alignment and using push rods which meet tolerances given in 7.3 7.3.. 12.4.1.2 12.4. 1.2 Passin Passing g throu through gh or alongs alongside ide obstructions obstructions such as boulders, bould ers, cobbles, coarse gravel, soil concretions, concretions, thin rock layers, or inclined dense layers will deflect the penetrometer tip and induce drifting. Note and record any indication of encountering such obstructions, and be alert for possible subsequent improp imp roper er pen penetr etrome ometer ter tip ope operat ration ionss as a sig sign n of ser seriou iouss directional drift. 12.4.1.3 12.4. 1.3 Penetr Penetrometer ometer inclination inclination is typica typically lly monitored in cone penetrometers. Impose limitations on inclination in the system sys tem to pre preven ventt dam damage age to pus push h rod rodss and non-symm non-symmetr etric ic loadin loa ding g of the pen penetro etromete meterr tip tip.. Gen Genera erally lly,, a 5° cha change nge in inclina inc linatio tion n ove overr 1 m of pen penetra etratio tion n can imp impose ose det detrim riment ental al push rod bending. Total drift of over 12° in 10 m of penetration imposes non-symetric loading and possible unreliable penetration resistance data. Push Rod Add Additio ition n Int Interr errupt uption ions— s— Short 12.4.2 Push Short durat duration ion interr int errupt uption ionss in the pen penetr etratio ation n rate dur during ing add additio ition n of eac each h new push rod can affect initial cone and friction sleeve readings at the beginning of the next push. If necessary, note and record the depths at which push rods are added and where long pauses may have affected initial startup resistances. Piezo zocon conee Por Porewa ewater ter Pr Press essur uree Dis Dissip sipati ation on 12.4.3 Pie Interruptions— Interrupti ons— Porewa P orewater ter pr press essure ure dis dissip sipati ation on stu studie dies, s, fo forr which whi ch sou soundi ndings ngs are sto stoppe pped d and rod loa load d is rel releas eased ed for varyin var ying g tim timee dur duratio ations, ns, can af affec fectt the ini initial tial con cone, e, fri frictio ction n 11
D5778 − 12 sleeve, and dynamic porewater pressure readings at resumptions of cone penetration. penetration. If dissip dissipation ation tests are perfo performed, rmed, be aware of possible rebound effects on initial excess porewater pressures. Note and record the depth and duration for which dissipation values are taken. 12.4.4 Interruptio If obstr obstruction uctionss Interruptions ns Due to Obstru Obstructions ctions— — If are encountered and normal advance of the sounding is stopped to bor boree thr throug ough h the obs obstru tructio ctions, ns, obt obtain ain fur furthe therr pen penetr etratio ation n resista res istance nce dat dataa onl only y aft after er the pen penetr etrome ometer ter tip has pas passed sed through the estimated zone of disturbance due to drilling. drilling. As an alternative, readings may be continued without first making the additional penetration and the disturbed zone evaluated from thes th esee da data ta.. No Note te an and d re reco cord rd th thee de dept pth h an and d th thic ickn knes esss of obstructions and disturbed zones in areas where obstructions are drilled through. 12.4.5 Excessive Thrust Capacity— If If excessive thrust pressure begins to impede the progress of the sounding, it may be necess nec essary ary to wit withd hdraw raw an and d ch chang angee fr frict ictio ion n red reduce ucers. rs. Alternately, sometimes friction may be reduced by withdrawing the penetrometer and rods up to one third to one half of the penetration depth and then repushing to depth at which the friction caused stopping. Continue collection of sounding data from the point of stopping. Note and record the delay time and depths to which the penetrometer was moved. Long delays and pauses may cause buildup of friction on the rods. Hold delays to th thee mi mini nimu mum m re requ quir ired ed to pe perf rfor orm m di diss ssip ipat atio ion n te tests sts or equipment repairs. 12.4.5 12. 4.5.1 .1 If a hig high h res resista istance nce layer is enc encoun ounter tered, ed, and the hydr hy drau aulic lic thr thrust ust mac machin hinee is ph phys ysica ically lly mo moved ved du durin ring g penetr pen etratio ation, n, ter termin minate ate the sou soundi nding. ng. Ano Another ther ind indicat icator or of reaching thrust capacity is the rebound of rods after they are released. The magnitude of rebound depends on the flexibility of the thrust machine and the push rods. An operator must become bec ome familiar familiar with the saf safee defl deflecti ection on of the system and decide when excessive deflections are being reached. 12.4.6 Unusual Occurrences— As A s da data ta ar aree re reco cord rded ed,, it is important to note unusual occurrences in testing. When penetrating gravels, it is important to note “crunching” sounds that may occur when particle size and percentage of coarse particles begin to influe influence nce penetration. penetration. Note and repor reportt all occur occurrences rences of coarse gravels.
hole clo hole closur suree sho should uld be mad madee to protect protect the wate waterr aqu aquife iferr. Details Det ails on var variou iouss meth methods ods for hol holee closur closuree are pro provid vided ed elsewhere (13 13)). 13. Calc Calculat ulation ion 13.1 Friction Cone Penetr Most elec electro tronic nic con conee Penetrometer ometers— s— Most penetrometers in use at the present time measure a change in voltage across a strain gauge element to determine change in length of the strain element. Using known constitutive relationships between stress and strain for the strain element, the applied force may be determined for the cone or friction sleeve. The applied force may then be converted to stresses using the basic equations given in 13.2 in 13.2 and and 13.3 13.3.. Since there are a wide variety of additional, optional measurements currently being obtaine obt ained d with ele electro ctronic nic con conee pen penetro etromete meters rs and new one oness being bei ng con continu tinually ally developed developed,, it is bey beyond ond the sco scope pe of this procedure to detail the makeup, adjustments, and calculations for these optional measurements. 13.2 Cone Resistance, qc —Required: q c 5 Q c / A c
(1 )
where: qc = cone resistan resistance ce MPa (for examp example, le, ton/ft ton/ft2, kgf /cm2, or bar), Qc = for force ce on cone cone kN (for (for example, example, ton, ton, or kgf ), and Ac = con conee base base area, area, typica typically lly 10 10 cm2, or 15 cm 2. Corrected ected Total Cone Resis Resistanc tancee (Req (Requir uired)— ed)— 13.2.1 Corr Calculation of corrected total cone resistance requires measurement of porewater pressures measured at the shoulder in the u 2 position. q t 5 q c 1 u 2 ~ 1 2 a n !
(2 )
where: qt = corrected corrected total total cone cone resistanc resistance, e, MPa (ton/f (ton/ftt2, kgf /cm2, bar, or suitable units for stress), porewater ater pressure pressure generated generated immediately immediately behind behind the u 2 = porew 2 cone tip, kPa (for example, tsf, kg f /cm , bar, or suitable units for pressure), and an = net are areaa ratio ratio (se (seee A1.7 A1.7)). 13.2.1.1 The correction 13.2.1.1 correction to total cone resistance is particularly important when porewater pressures are generated during penetration (for example, saturated clays, silts, and soils with appreciable fines). Generally, the correction is not so significant for CPTs in clean sands, dense to hard geomaterials, and dry soils. The correction is due to porewater pressures acting on opposing sides of both the face and joint annulus of the cone tip (4, 1, 6, 8).
12.5 Withdrawal: 12.5.1 Withdraw the push rods and penetrometer tip as soon as possible after attaining complete sounding depth. 12.5.2 Upon 12.5.2 Upon com comple plete te with withdra drawal wal of the pen penetr etrome ometer ter,, inspect the penetrometer tip for proper operation. The friction sleev sle evee sh shou ould ld be ab able le to be ro rotat tated ed th thro roug ugh h 36 360° 0° by ha hand nd withoutt detecta withou detectable ble bindi binding. ng.
NOTE 9—In all cases, the total value q t should be used, substituted for (or both) qc, wherever possible. In no cases should q c be backdetermined from qt for use in equations, charts, formulae, or other purposes. It is always a forward procedure with corrected total qt to be preferred.
12.5.3 12.5. 3 Record baseline baseline readin readings gs with the penetrometer penetrometer tip hangin hang ing g fr freel eely y in air air,, or in wa water ter,, ou outt of di dire rect ct su sunl nlig ight ht.. Compar Com paree bas baselin elinee rea readin dings gs with ini initial tial bas baselin elinee rea readin ding g for requirements given in 10.1.2.1 10.1.2.1..
13.2.1.2 13.2. 1.2 Empiri Empirical cal adjustment factors based on select soil types have been developed for some pressure elements in the u1 position, however these are not reliable. On a site-by-site basis, a relationship between u 1 and u 2 may be possible.
12.6 Hole Closure— In In certain cases, it may be prudent or required by state law or specificiations, that the cone hole be filled fill ed,, se seale aled, d, or gr grou oute ted d an and d cl clos osed ed af after ter th thee so soun undi ding ng is comple com pleted. ted. For exa exampl mple, e, in com comple plex x gro ground undwate waterr reg regimes imes,,
13.3 Friction Sleeve Resistance, f s —Required: f s 5 Q s / A s
12
(3 )
D5778 − 12 u o 5 ~ z 2 z w ! γ w
where: f s = friction friction sleeve sleeve resista resistance nce kPa kPa (ton/ft (ton/ft2, kgf /cm2, bar, or suitable units for stress), Qs = for force ce on frictio friction n sleeve sleeve kN (ton, (ton, kgf , or suitable units for force), and areaa of friction friction sleeve sleeve,, typically typically 150 150 cm2 for 10-cm 2 As = are 2 tip, or 200 to 300 cm for larger 15-cm 2 cones.
For soils above the groundwater table that are saturated due to full capillarity, Eq 6 is also applicable. For dry soils above the groundwater table, it is commonly adopted that u o = 0. In partial par tiallyly-sat satura urated ted soi soils ls (va (vados dosee zon zone), e), the there re can be gre great at transient variations and variability in the u o profile. where: hw = heig height ht of wa wate terr, m (o (orr fe feet et), ), ev eval alua uate te fr from om si site te conditions, unit it we weig ight ht of (f (fre resh sh)) wa wate terr = 9. 9.8 8 kN kN/m /m3 (or 62. 62.4 4 γw = un lbs/ft3), z = dep depth th of of inter interest est (m (m or fee feet), t), and zw = depth to the groundwa groundwater ter table (phre (phreatic atic surface). surface).
NOTE 10—A corrected sleeve friction resistance may also be obtained (2 2, 3 3,, 1 1,, (f t), yet this requires both u2 and u3 measurements simulaneously ( 5, 6, 8). Thus, the raw f s has bee been n acc accept epted ed for pra practi ctical cal rea reason sons. s. A simplified simpli fied correction has been adopted by select selected ed orga organizati nizations ons (for (8 8) ). example, (
13.4 Friction Ratio, R f —(Optional): R f 5 ~ f s / q c ! · 100
(4)
In layered soils with multiple perched aquifers the assumption of a single height of water may be in error.
where: R f = frictio friction n rati ratio, o, %, f s = frictio friction n sleeve resista resistance nce kPa (ton/f (ton/ftt2, kg f /cm2, bar, or suitable units for stress), = cone resista resistance nce kPa (ton/f (ton/ftt2, kgf /cm2, bar, or suitable qc units for stress) (See Note 2 for 2 for use of q t), and 100 = con conver versio sion n from from dec decimal imal to per percen cent. t.
13.6 Normalized CPT Measurments In the latest soil behavioral clas ioral classifi sificati cation on cha charts rts and CPT inte interpr rpretat etation ion meth methods ods,, normalized readings for cone tip resistance, sleeve friction, and porewater pressure are utilized (1, 6, 14 14)), as defined below. 13.6.1 13.6. 1 Normal Normalized ized cone tip resista resistance: nce: Q 5 ~ q t 2 σ vo! / σ vo'
13.4.1 Determ 13.4.1 Determination ination of the frictio friction n ratio requi requires res obtaining a con conee res resista istance nce and friction friction sleeve resistanc resistancee at the same point in the soil mass. The point of the cone is taken as the refere ref erence nce dep depth. th. Typi ypicall cally y, a pre previo vious us con conee tip res resista istance nce read re adin ing g at fr fric ictio tion n sl sleev eevee mi midp dpoi oint nt de dept pth h is us used ed fo forr th thee calculations. For the 10-cm2 penetrometer, the standard offset is 100 mm. If an offset other than midheight is used it must be reported.
(7)
13.6.2 Normal Normalized ized Por Porewa ewater ter Pr Press essur uree Par Parame ameter ter,, B q — This pa This para rame meter ter is no norm rmall ally y ca calcu lcula lated ted wi with th th thee sh shou ould lder er porewater pressure measurement (location immediately behind the cone tip), designated u 2. B q 5 ∆ u / ~ q t 2 σ vo!
(8 )
13.6.3 13.6. 3 Normal Normalized ized friction ratio: F 5 f s / ~ q t 2 σ vo!
NOTE 11—In some cases, if readings are compared at the same point in a soil mass which has alternating layers of soft and hard materials erratic friction ratio data will be generated. This is because cone resistance is sensed, to varying degrees, ahead of the cone. The erratic data may not be representati repres entative ve of soils actually presen present. t. NOTE 12—The 12—The fricti friction on sleev sleevee resis resistance tance and fricti friction on ratio obtained from the mechan mechanical ical frictio friction n cone penetrometers penetrometers will dif differ fer consid considerably erably from values obtained from electronic friction cone penetrometers. When using soil classification charts that use R f and qc, it is important to use charts based on correlations for the type of penetrometer being used.
(9 )
where: u = excess excess pore pore wate waterr pressu pressure re (u (u 2 − uo) (see 3.2.13 (see 3.2.13)), ∆u ∆ uo = estimate estimated d equilibriu equilibrium m water pressu pressure, re, or hydro hydrostatic static porewater (see 13.5.3 13.5.3)), vertical al overbur overburden den stress stress,, and σ vo = total vertic effectiv fectivee overburd overburden en stress stress = σvo – uo σ vo' = ef The total overburden stress is calculated:
13.5 Porewater Pressure Data: 13.5.1 13.5. 1 SI metric units for reporting porewater porewater pressure pressure data are kPa. Conversi rsion on of Mea Measur sured ed Por Porewa ewater ter Pr Press essur ures es to 13.5.2 Conve Equivalent Height of Water—Optional— If I f it is de desi sire red d to display dis play por porewa ewater ter pre pressu ssure re in equ equiva ivalen lentt hei height ght of wat water er,, conver con vertt the dyn dynamic amic or stat static ic wat water er pre pressu ssures res to hei height ght by dividing pressure by the unit weight of freshwater, γw = 9.8 kN/m3 (62.4 lbf /ft3). For salt water, use γ use γ w = 10.0 kN/m3 (64.0 lbf/ft3). 13.5.3 Estim Estimate ate of Equ Equilibr ilibrium ium Por Porewate ewaterr Pr Pressu essure re— — Excess porewater pressure can only be calculated by knowing equilibrium pore water pressure, uo (see (see 3.2.14 3.2.14)). The equilibrium riu m wat water er pre pressu ssure re can be mea measur sured ed by dis dissip sipatio ation n test or estimated by calculation as follows: u o 5 estimated equilibrium water pressure 5 h w · γ w
(6 )
σ vo 5
( ~ γ ∆ ∆ z z ! ti
i
(10)
where: layer thic thickne kness, ss, and ∆ zi = layer total al so soil il unit unit weigh weightt for laye layerr. γti = tot 14. Repo Report rt 14.1 Repor Reportt the follow following ing information: information: 14.1.1 14. 1.1 General—Ea General—Each ch sou soundi nding ng log sho should uld pro provid videe as a minimum: 14.1.1.1 14.1. 1.1 Operat Operator or name, 14.1.1.2 14.1. 1.2 Projec Projectt infor information mation,, 14.1.1.3 14.1. 1.3 Featur Featuree notes, 14.1.1.4 14.1. 1.4 Groun Ground d surface elevation and water surfac surfacee elevation (if available), 14.1.1.5 14.1. 1.5 Sound Sounding ing locatio location, n, includ including ing coord coordinates inates 14.1.1.6 14.1. 1.6 Sound Sounding ing number, number, and 14.1.1.7 14.1. 1.7 Sound Sounding ing date. 14.1.2 14.1. 2 Report Reportss shoul should d contain information information concerning: concerning:
(5 )
In saturated soils below the groundwater level, the hydrostatic case is obtained from: 13
D5778 − 12 14.1.2.1 Equipment Used— Design Design drawings and data on all sensors, 14.1.2.2 14.1. 2.2 Graph Graphical ical data, 14.1.2.3 14.1. 2.3 Electro Electronic nic digital data or tabula tabularr data (opti (optional), onal), 14.1.2.4 14.1. 2.4 Proce Procedures dures followed, followed, and 14.1.2.5 Calibration Information— For For all sensors, information required in Section 10 10.. 14.1.3 14.1. 3 The report should should contain a text that discusses discusses items required requir ed in 14.2 and 14.3. 14.3. Each sou soundi nding ng sho should uld be doc docuumented with: 14.1.3.1 14.1. 3.1 Soun Sounding ding plot. 14.1.3.2 Accompanying Tabular Output— Tabular Tabular output is considered optional due to its bulk. It is optional as long as computer data files are preserved and archived for later use. 14.1.3.3 Computer Provide in ASCII form format, at, Computer Data Files— Provide spreadsheet file, or text, or other common file format. Compute pu terr da data ta file filess mu must st co cont ntai ain n he head ader er as re requ quir ired ed in 14.1, 14.1, soundi sou nding ng log inf inform ormatio ation. n. Cer Certain tain int interp erpret retatio ation n pro progra grams ms require data to be in a particular format. It is the responsibility of the user to determine acceptable formats. 14.1.3.4 14.1. 3.4 The comments should contain notes on equipment and procedures, particular to the individual sounding.
14.2.7 Method used to prov 14.2.7 provide ide reaction force—with force—with notes as to possible surface deformations, 14.2.8 14. 2.8 Loc Locatio ation n and typ typee of fri frictio ction n red reduct uction ion sys system tem (if any), 14.2.9 14.2. 9 Method of recording recording data, 14.2.10 14.2. 10 Condit Condition ion of push rods and penetrometer penetrometer tip after withdrawal, 14.2.11 14.2. 11 Any special dif diffficulties or other observations observations concerning performance of the equipment, 14.2.1 14. 2.12 2 Det Details ails on pie piezoc zocone one des design ign,, filte filterr elem element ents, s, and fluid conditioning procedures, and 14.2.13 14.2. 13 Info Information rmation on other sensing devices used durin during g the sounding.
14.2 Equipment— The The report should include notes concerning: 14.2.1 Penetrometer manufacturer, manufacturer, 14.2.2 14.2. 2 Types of penetr penetrometer ometer tips used, 14.2.3 14.2. 3 Penetr Penetrometer ometer details such as net area ratio, friction friction sleeve end areas, location and types of sensors, location and type of friction reducers, 14.2.4 14. 2.4 Of Offse fsett bet betwee ween n tip and slee sleeve ve res resista istance nce use used d for friction ratio determination, 14.2.5 14.2. 5 Serial numbers numbers of penetr penetrometer ometer tips, 14.2.6 14.2. 6 Type of thrust machine,
14.4 Graphs— Every Every rep report ort of fri frictio ction n con conee pen penetra etratio tion n sounding is to include a cone tip resistance plot, qc MPa, or preferably total cone tip resistance, q t MPa (or ton/ft 2, kgf /cm2, bar, or other acceptable unit of stress) with depth below ground surfac sur facee m (ft (ft), ), fri frictio ction n slee sleeve ve res resista istance nce,, f s, kP kPaa (t (ton on/f /ftt2, kgf /cm2, bar, or other acceptable units of stress), and friction ratio, R f (%), on the same plot. (See Fig. 4 and Fig. 5 for example examp le plots.) As a minimu minimum, m, the plot shoul should d provide general general inform inf ormatio ation n as out outline lined d in 14.1. 14.1. Electronic Electronic piezoc piezocone one penetrome etr ometer ter sou soundi ndings ngs sho should uld pro provid videe an add additio itional nal plo plott of 2 2 porewa por ewater ter pre pressu ssure re kPa (or lbf /in. , kgf /cm , ba barr, or ot othe herr
14.3 Calibration Certifications— For For each project the report should include the load range calibrations of the cones used that were performed in accordance with Section 10 Section 10.. The report should include the initial and final baseline readings for each sounding. Calibration records for the porewater pressure transducers are required as given in 10.2. 10.2. If the project requires calibrations of other sensors they should also be submitted in final reports.
FIG. 4 Exampl Example e Graph Presentation Presentation Results Results from a Conve Convention ntional al Piezocone Penetration Penetration Test
14
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FIG. 5 Illust Illustrative rative Piezocone Piezocone Graph Showi Showing ng Tip Resist Resistance, ance, Sleeve Friction, Penetration Penetration Porewater Porewater Pressure, and Fricti Friction on Ratio
Friction—Su n—Subtract btraction ion Cones— Standard 15.1.2 Sleeve Frictio Standard deviation of 15 % FSO.
acceptable units of pressure) versus depth, m (ft). Porewater reading read ingss can be plo plotted tted as pre pressu ssures res,, or alte alterna rnative tively ly,, the pressure may be converted to equivalent heights of water (that is, hw = u2 / γw). 14.4.1 14.4. 1 Symbo Symbols ls qt and f s for tip and sleeve resistance are accepted by the International Society for Soil Mechanics and Geotechnical Engineering ( (4 4, 1 1,, 5, 9 9)). 14.4.2 14. 4.2 For uni unifor form m pre presen sentati tation on of dat data, a, the ver vertica ticall axi axiss (ordinate) (ordi nate) should display depth and the horizontal horizontal axis (abscissa) should display the test values. There are many preferences in plotting such that uniform plotting scales and presentation will not be required.
Friction—In n—Indepen dependent dent Cones— Standard 15.1.3 Sleeve Frictio Standard deviation of 5 % FSO. 15.1.4 Dynamic Por Strongly depen dependent dent Porewater ewater Pres Pressur sure— e— Strongly upon upo n ope operat ration ional al pro proced cedure uress and ade adequa quacy cy of satu saturati ration on as descri des cribed bed in 11.2. 11.2. When When car caref eful ully ly ca carr rried ied ou outt a st stan anda dard rd deviation of 2 % FSO can be obtained.
15.2 Bias— This This test method has no bias because the values determined can be defined only in terms of this test method. 14)) report qt repeatability of the two NOTE 13—Jefferies and Davies (14 different soundings in compact clean sand using two different cones by the same manufacturer. Approximately 50 % of the data lay within 8 % of the average of the two tests, and 90 % of the data lay within 15 % of the average. In this trial the transducers (that conformed to the requirements in A1.5 in A1.5)) were loaded to between one tenth and one fifth of their rated FSO, so confirming a standard deviation of better than 2 % FSO.
15. Pre Precisi cision on and Bias 15.1 Precision— There There are little direct data on the precision of th this is tes testt me meth thod od,, in pa part rtic icul ular ar be beca caus usee of th thee na natu tura rall variability of the ground. Committee D-18 is actively seeking comparative compar ative studies. Judgi Judging ng from observed repeatability repeatability in approximate uniform deposits, persons familiar with this test estimate its precision as follows: Cone Resista Resistance— nce— Provid 15.1.1 Cone Provided ed tha thatt com compen pensati sation on is made for unequal area effects as described in 13.2.1 13.2.1,, a standa standard rd deviation of approximately 2 % FSO (that is, comparable to the basic electromechanical combined accuracy, nonlinearity, and hysteresis).
16. Keyw Keywords ords 16.1 cone penetration test; cone penetrometer; explorations; explorations; field test; friction resistance; geotechnical test; in-situ testing; penetration penetr ation tests; penetr penetrometer ometer;; piezoco piezocone; ne; point resist resistance; ance; porewater porew ater pressu pressures; res; resist resistance; ance; sleeve friction; soil invest investigaigations
15
D5778 − 12 ANNEX (Mandatory Information) A1. CALIBRA CALIBRATION TION REQUIREMENTS ON NEWLY NEWLY MANUFACTURED MANUFACTURED OR REP REPAIRED AIRED ELECTRONIC FRICTION CONE AND PIEZOCONE PENETROME PENETROMETERS TERS
A1.1 Introduction: A1.1.1 This annex descr A1.1.1 describes ibes procedures procedures and requirements requirements for calibrating electronic cone penetrometers. The evaluation of cone penetrometer calibration as described in this annex is a qua quality lity ass assura urance nce sta standa ndard rd for new newly ly man manufa ufactu ctured red and repair rep aired ed pen penetr etrome ometer ter tips tips.. Man Many y of the stan standar dards ds may be imprac imp ractic tical al to eva evalu luate ate un unde derr fiel field d op opera eratin ting g co cond nditi ition ons. s. Theref The refore ore,, dete determi rminat nation ion of the these se cali calibra bratio tion n err errors ors for any individual penetrometer tip should be performed in a laboratory environment under ideal conditions by the manufacturer or other oth er qu quali alified fied pe perso rsonn nnel el wit with h nec necess essary ary kn know owled ledge, ge, experience, experi ence, and facilitie facilities. s. A1.1.2 A1. 1.2 The electronic electronic con conee pen penetr etrome ometer ter is a deli delicate cate instrumentt sub strumen subject jected ed to sev severe ere fiel field d con condit dition ions. s. Pro Proper per use of such an instrument requires detailed calibration after manufacture and continuous field calibrations. Years of cone penetrometerr de ete desi sign gn an and d pe perf rfor orman mance ce ex expe peri rien ence ce ha have ve re resu sulte lted d in refined cone designs and calibration procedures which make the electronic cone penetrometer a highly reliable instrument. Reports of these experiences form the basis for requirements in this annex (3, 4 4,, 1, 5 5,, 11 11,, 12 12)).
FIG. A1.1 Defini Definition tion of Calibration Calibration Terms Terms for Load Cells and Transducers ( Transducers (1 1, 10 10))
A1.1.3 The required calibration tolerances developed in this annex are based on subtra subtraction ction type electronic cone penetr penetromometers. eter s. The These se pen penetro etromete meters rs are mor moree rob robust ust tha than n elec electro tronic nic cone penetrometers with independent tip and sleeve load cells and are the most wid widely ely use used d des design ign.. The subtractio subtraction n typ typee penetrometer, however, has less precision due to the subtraction process (5, 11 11)). As a result, calibration tolerances given heree are con her consid sidere ered d max maximu imum m valu values es and req requir uireme ements nts for more sensitive cone penetr penetrometer ometerss imply smaller tolera tolerances nces having greater precision. precision. The calibr calibration ation process consists of loading the penetrometer tip with reference forces and pressures and then comparing measured output to the reference.
Cone pe Cone pene netr trom omete eterr tip tipss us usua ually lly ar aree av avail ailab able le in no nomin minal al capacities of 2, 5, 10, and 15 metric tons. Typical full-scale outputs for these penetrometer tip ranges as follows: Nominal Capacity
Full-Scale Output of Cone, q Cone, q c
Full-Scale Output of Friction Sleeve, f Sleeve, f ton/ft2 kPa
s
metric tons 2 5 10 15
A1.1.4 Calibrations in the laboratory environment should be be performed with the complete penetrometer system to be used in the field. The same make and model computer, cable, signal conditioning system, and penetrometer to be used in the field shall be calibrated in the laboratory. Depending on the components of the system some components may be substituted with accepta acceptable ble replace replacements. ments. Each indiv individual idual penetr penetrometer ometer must mu st be tes teste ted d ov over er a ra rang ngee of lo load adss to as assu sure re ad adeq equa uate te performance.
to n / ft2 2 00 5 00 1 0 00 1 0 00
MPa 20 50 100 100
2 5 10 10
20 0 50 0 10 0 0 10 0 0
A1.2.3 It is important to check with the manufacture manufacturerr on the full scale output of electronic cone penetrometer tips to avoid overloading overl oading and damag damaging ing penetr penetrometer ometer tips. Values: A1.3 Zero Load Baseline Values:
A1.3.1 ZeroZero-load load output variation variation of the cone penetrometer penetrometer during testing and calibration is a reliable indicator of output stabilit stab ility y, inte interna rnall O-r O-ring ing fri frictio ction, n, and temp tempera eratur ture-i e-indu nduced ced apparent load. The variation in zero load output is affected by temperat temp erature ure fluct fluctuati uation on beca because use temp temperatu erature re comp compensa ensated ted strain gages do not compensate for material effects and system component effects ( (3 3, 4 4,, 1, 5 5,, 10 10)).
Transducer Calibrations: A1.2 Terms Related to Force Transducer
A1.2.1 Fig. A1.1 is A1.1 is a graphical depiction of terms related to transducer calibrations and defines the concepts of zero-load error, nonlinearity, hysteresis, and calibration error ( (3 3, 1, 10 10)).
A1.3.2 Systems with microp microprocess rocessors ors prov provide ide “refer “reference ence baseline” values for the transducers that are not equal to zero but are measured positive or negative values depending on the electronics of the system. For the particular penetrometer and
A1.2.2 To eva A1.2.2 evalua luate te sev severa erall of the these se val values ues,, the FSO (full scale output) of the penetrometer tip is needed. The manufacturer shall provide full scale output information for the system. 16
D5778 − 12 penetrometer system used, the baseline values should remain relativ rela tively ely con constan stantt thr throug ough h the lif lifee of the pen penetro etromete meterr. As testing is performed in the field, the baseline resistances are monitor mon itored ed for changes. changes. If lar large ge cha change ngess are not noted ed the penetrometer should be loaded to check for linearity and possible damage. Evaluate the zero-load error during load range calibrat br atio ion n by tak takin ing g th thee di difffe fere renc ncee be betw tween een in initi itial al an and d fin final al baselinee values baselin values..
same lev same level el of app applied lied force in loa loadin ding g and unloadin unloading g and dividing by cone FSO. Calculate calibration error by taking the difference between the best-fit-straight line cone resistance and actual cone resistance and dividing by the actual cone resistance. Calibration error can become larger with smaller measured sur ed out output putss and and,, the theref refore ore,, it is not evaluated evaluated at loa loadin dings gs equivalent to less than 20 % of cone FSO. A1.4.3.1 A1.4.3 .1 When calibrating the penetr penetrometer ometer,, monito monitorr the friction frictio n sleeve resistance to evalua evaluate te appar apparent ent load transf transfer er.. With a subtraction-type electronic cone penetrometer tip, the appare app arent nt fri frictio ction n sle sleeve eve res resista istance nce is cau caused sed by elec electri trical cal subtraction error, crosstalk, and any load transferred mechanically to the sleeve. With a cone, that provides for independent cone and sleeve measurements, apparent friction sleeve resistances are caused by electrical crosstalk and mechanical load transfer transf er.. Appar Apparent ent load transfer must be less than 1.5 % of FSO of the friction sleeve (1000 kPa). A1.4.3 A1. 4.3.2 .2 Max Maximu imum m non nonlin linear earity ity sho should uld be 0.2 %, max maxiimum calibration error should be 0.5 %, and maximum apparent load transfer should be 1.2 %. For this calibration, the zero load error was zero. Hysteresis was not evaluated in this example because the testing machine was incapable of producing the exact same force on the loading and unloading steps.
Thermal Stab Stability ility— — For A1.3.3 Thermal F or ens ensur uranc ancee of the therma rmall stability, evaluate a particular design of a newly manufactured cone under a range of temperature conditions. Newly manufactured penetrometer tips are first cycled to a minimum of 80 % of FSO five times at room temperature, to remove any residual nonlinearity. After cycling, establish an initial referencee bas enc baselin elinee val value ue at roo room m tem temper peratu ature re aft after er the cone has been be en ele electr ctrica ically lly po powe were red d fo forr ab abou outt 30 min min.. To ev evalu aluate ate thermal stability, stabilize the penetrometer tip at temperatures of 10 and 30°C and new baseline values are obtained. The change in baseline values must be ≤ 1.0 % FSO of either cone or friction sleeve resistances. Range Calibration: A1.4 Load Range
A1.4.1 A1.4. 1 Calibra Calibrate te newly manufactured manufactured or repaired cone penetrometers over a range of loads after production or repair. Load test the cone penetrometer system in a universal testing machine or specially designed cone penetrometer calibration device capable of independently loading the cone and friction sleeve. slee ve. If a uni univer versal sal tes testing ting machine machine is use used, d, a cali calibra bration tion certifica cert ificate te (cu (curre rrent nt with within in the last yea year) r) in acc accord ordanc ancee with Practice E4 Practice E4 must must be available. If a cone calibration apparatus is used, it shoul should d also have a calibra calibration tion document document curre current nt within the last yea yearr. The cali calibra bratio tion n doc docume ument nt sho shows ws that app applied lied forces for ces or mass masses es are traceable traceable to sta standa ndard rd for forces ces or mas masses ses retained by the National Institute of Standards and Technology. The universal testing machine or cone calibration devices must be capable of loading the penetrometer tip to 100 % FSO.
A1.4.4 For calibration calibration of the frictio friction n sleeve element, apply the forces in seven increments at 0, 2, 5, 10, 25, 50, and 75 % of FSO FSO.. Non Nonlin lineari earity ty,, hys hyster teresis esis,, and cali calibra bratio tion n err error or are evaluated in the same manner as calibrations for the cone tip reading. readin g. Durin During g frictio friction n sleeve calibration, calibration, monito monitorr cone tip resista res istance nce to eva evalua luate te app appare arent nt load transfer transfer tha thatt was not apparent in this calibration. A1.5 Force Transducer Transducer Calibration Requirements: Requirements: A1.5.1 Calibration Calibration requi requirement rementss develo developed ped for electro electronic nic cone co ne pe pene netr trom omete eters rs ar aree ba based sed on pa past st ex expe perie rienc ncee wi with th subtractionsubtr action-type type electronic cone penetr penetrometer ometerss and, as a result of this experience, represent the minimum precision requirement of electronic cone penetrometers. In cases where a higher level of precision is required, stricter calibration requirements would be required. Newly manufactured or repaired electronic cone penetrometers are required to meet the following requirements:
A1.4.2 Sele A1.4.2 Selectio ction n of loa loadin ding g step stepss and max maximu imum m loa loadin ding g varies depending on need and application. Select the load steps and an d ma maxi ximu mum m lo load ad to co cove verr th thee ra rang ngee of in inte tere rest st an and d no nott necessarily the maximum capacity of the cone. Some calibrations stress more frequent load steps at lower loads to evaluate weaker materials. Selection of more frequent lower load steps may result in highe higherr levels of calibra calibration tion error since the best fit line is more influenced by the low range data.
Calibration Parameter Zero Ze ro-l -loa oad d er erro rorr Zero-load thermal stability Nonlinearity
A1.4.3 A1. 4.3 Per Perfor form m the loading loading afte afterr the cone is sub subject jected ed to five cycles of compressive loading and reference baselines, or internal zeroing, have been obtained at room temperature. The penetr pen etrome ometer ter is load loaded ed in a min minimu imum m of six incremen increments ts at forces equivalent to 0, 2, 5, 10, 25, 50, and 75 % FSO. At each increment of force, record both cone and sleeve resistances. Compute the actual cone tip resistance by dividing the applied force by the cone base area. The friction sleeve resistance is taken as the corresponding axial force over the sleeve area. Determine the “best fit straight line” by linear regression of applied force and measured output. The linearity is the difference between measured cone resistance and best-straight line cone resistance divided by the cone FSO. Evaluate hysteresis by com compar paring ing the dif differ ferenc encee bet betwee ween n con conee res resista istance nce at the
Hysteresis Cali Ca libr brat atio ion n er erro rorr
El em e nt Tip an and d sl slee eeve ve Cone tip and sleeve Cone tip Sleeve Tip and sleeve Con one e ti tip p Sleeve
Appa Ap pare rent nt lo load ad
Whil Wh ile e lo load adin ing g co cone ne tip While loading sleeve
Requirement ± 0.5 % FSO # ± 1.0 % FSO #
± 0.5 % FSO ± 1.0 % FSO # ± 1.0 % FSO # ± 1.5 % MO at >20 % FSO # ± 1.0 % MO at >20 % FSO # ± 1.5 % FSO of sleeve transfer # ± 0.5 % FSO of cone tip # #
A1.6 Pressure Transdu Transducer cer Calibrations: A1.6.1 Newly manufactured manufactured or repair repaired ed pressure transductransducers shall be supplied with a load range calibration provided by the manufacturer. The load range calibration shall consist of a minimum of six points of loading to at least 75 % of FSO. The 17
D5778 − 12 applied pressures shall be traceable to reference forces maintained by NIST. The calibration shall meet the manufacturer’s stated tolerances. Minimum requirements are linearity better than 1 % of FSO and zero load error less than 67 kPa (61.0 lb/in.2).
A1.7.3 A1.7 .3 In or orde derr to ca calc lcul ulat atee th thee co corr rrec ecte ted d to tota tall co cone ne resistance, resista nce, qt, as shown shown in 13.2.1, 13.2.1, it wi will ll be ne nece cess ssar ary y to determine the area ratio of the cone. The penetrometer can be enclosed in a sealed pressure vessel (for example, triaxial cell) and water pressures should be applied as shown in the example in Fig. in Fig. A1.3. A1.3. The net area ratio is then used in computing the corrected total tip resistance.
A1.6.2 The transducer A1.6.2 transducer shall be subjected to regular periodic periodic inspection meeting requirements in A1.6.1 in A1.6.1..
A1.8 Other Calibrations—Other sensors sensors such as inclination, tempera temp eratur ture, e, etc. may req requir uiree cali calibra bration tion dep depend ending ing on the requirement requi rementss of the invest investigation igation.. Perfo Perform rm such calibrations calibrations usin us ing g si simil milar ar tec techn hniq ique uess gi give ven n in th this is an anne nex x or by ot othe herr reference refer ence proce procedures dures.. Report such calibr calibrations ations when requi required. red.
A1.7 Correc Correction tion of Tip and Sleeve Areas: A1.7.1 The conceptual A1.7.1 conceptual regions where water pressures can act on the cone tip and sleeve elements are shown in Fig Fig.. A1. A1.2 2. Wate aterr pr pres essu sure re th that at act actss be behi hind nd th thee co cone ne tip wi will ll re redu duce ce measured measur ed cone resista resistance, nce, qc, by th thee ma magn gnit itud udee of wa wate terr pressu pre ssure re acti acting ng on unequal unequal are areas as of the tip geo geomet metry ry.. It is therefore advantageous to use a penetrometer having a net area ratio a n = 0.80 in order to minimize the effect of the correction (4, 1 1)). Water pressure may also act on both ends of the sleeve, resulting resulti ng in an imbalance of forces if the sleeve is not designed with equal effective end areas. The water pressures acting on the ends of the sleeve are not just a function of geometry, they aree al ar also so a fu func nctio tion n of th thee lo loca catio tion n of wa wate terr se seals als.. Wat ater er pressures during penetration are not often measured at both ends en ds of th thee sl sleev eevee (t (tha hatt is is,, sim simul ultan taneo eous us u2 and and u3) s o a correction is not normally made for f s ( (5 5).
A1.9 Documentation of Calibrations: A1.9.1 Lab A1.9.1 Labora orator tory y cali calibra bratio tion n doc docume uments nts con consis sistin ting g of a short report on the equipment and methods of testing, along with wi th tab tables les an and d fig figur ures es si simil milar ar to th thos osee in th this is an anne nex, x, ar aree required for the following occurrences: A1.9.1.1 A1.9.1 .1 When new penetrometer penetrometer tips are receiv received, ed, and A1.9.1.2 A1.9.1 .2 When damaged penetrometer penetrometer tips are repaired. A1.9.2 The report must be certified by a regis registered tered profesprofessional engineer or other responsible engineer with knowledge and exp experie erience nce in mate materia rials ls test testing ing for qua quality lity ass assura urance nce.. Calib Cal ibra ratio tion n do docu cumen ments ts ar aree re reta tain ined ed on fil filee by th thee of offfice icess responsible for performing soundings and should be updated at required requi red interv intervals. als. For contr contract act sound soundings, ings, calibration documents should be obtained prior to contract acceptance and after testing on unaltered equipment.
A1.7.2 A1.7. 2 Equal end area fricti friction on sleeves should be required for use and should be designed by the manufacturer. The best method meth od for eva evalua luatin ting g slee sleeve ve imb imbalan alance ce is to seal the pen pen-etrometer in a pressure chamber and apply forces to measure the sleeve resistance after zeroing the system. Manufacturers should sho uld perform perform this check for a par particu ticular lar des design ign to ass assure ure minimal imbalan imbalance. ce.
A1.9.3 If the electro electronic nic cone penetrometer penetrometer meets the field calibration requirements given in 10.1.3 in 10.1.3,, it is only necessary to
FIG. A1.2 Schematic of Net Area Ratio (a n) for Corrections of Cone Tip Resistances (6 (6)
18
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FIG. A1.3 Illust Illustrative rative Example Determinatio Determination n of Unequal End Area for Correc Correction tion of Tip Resist Resistances ances Using Pressurized Pressurized Triaxial Cell Calibration
adjust the penetrometer tip to the laboratory requirements on a yearly basis. Cone penetrometers should be calibrated using laboratory procedures prior to use on each new project, but
they do not need to meet calibration tolerances as required for newly manufactured cones.
REFERENCES (1) Lunne, T., Robertson, P.K. and Powell, J.J.M. (1997), Cone Penetration Testing in Geotechnical Practice, Blackie Academic/Routledge Publishing, New York, 312 pages. (2) Tumay, M.T., Boggess, R.L., Acar, Y. (1981). “Subsurface Investigation with Piezocone Penetrometer,” ASCE GSP on Cone Penetration Testing and Experience, St Louis, MO., 325-342 (3) Zuidb Zuidberg erg,, H.M H.M., ., Sch Schaap aap,, L.H L.H.J. .J.,, and Ber Bering ingen, en, F.L (19 (1982) 82).. “A Penetromete Penet rometerr for Simult Simultaneous aneously ly Measu Measuring ring of Cone Resis Resistance, tance, Pr Proceedi oceedings ngs of the Sleevee Fricti Sleev Friction on and Dynam Dynamic ic Pore Pressure,” Pressure,” Second Secon d Eur European opean Symp Symposium osium on Penetr Penetration ation Testing, Vol ol.. 2, Amsterdam, 963-970 (4) Campanella, R. G., and Robertson, P. P. K. (1988), “Current status of the Penetration Testing 1988 (Proceedings, ISOPT piezocone piezoc one test,” Penetration ISOPT-1, -1, Orlando), Vol. 1, Balkema, Rotterdam, 93–116. (5) Intern Internati ationa onall Ref Refer erenc encee Sta Standa ndard rd for the Con Conee Pen Penetr etrati ation on Test (1999), Technical Committee TC 16, ISSMGE, Proceedings, 121th Europe Eur opean an Con Conf. f. on Soi Soill Mec Mechan hanics ics & Geo Geotec techni hnical cal Eng Engine ineeri ering ng (Copenhagen), Vol. 3, Balkema, Rotterdam, 2195–2222. (6) Jamiolkows Jamiolkowski, ki, M., Ladd, C.C., Germaine, J.T. and Lancel Lancelotta, otta, R. (198 (1 985) 5),, “N “New ew de deve velo lopm pmen ents ts in fie field ld an and d la lab b te test stin ing g of so soil ils, s,””
11th Intern Internation ational al Confer Conference ence on Soil Mecha Mechanics nics & Proceedings, 11th Foundation Engineering, Vol. 1, San Francisco, 57–154. (7) Mayne, P.W Synthesis 368 on Cone Penetration Penetration Testing, .W.. (2007), Synthesis NCHRP 20-05 (Task 37-14), National Academy Press, Washington, D.C., 162 p. (8) Mulabdić, M., Eskilson, S., and Larsson, R. (1990), “Calibration of piezocones for investigations in soft soils and demands for accuracy of the equipment,” SGI Varia No. 270, Swedish Geotechnical Insitute, Linköping, 62 p. (9) DeBeer, E.E., Goelen, E., Heynen, W.J. W.J. and Joustra, K. (1988). “Cone penetration penetr ation test: Intern International ational reference test proced procedure,” ure,” Penetration Testing 1988, (Proc (Proceeding eedings, s, ISOP ISOPT T-1, Orlan Orlando), do), Vol. Vol. 1, Balke Balkema, ma, Rotterdam, 27–52. (10) Schaap, Schaap, L. H. J., and Zui Zuidbe dberg, rg, H. M. (19 (1982) 82),, “Me “Mecha chanic nical al and electrical aspects of the electric cone penetrometer tip,” Proceedings of the Second European Symposium on Penetration Testing , Vol. 2, Amsterdam, 841–851. (11) DeJong, J.T, Yafrate, N.J., and DeGroot, D.J. (2007), “Design of a miniature miniatu re piezop piezoprobe robe for high resolu resolution tion strati stratigraphi graphicc profi profiling,” ling,” ASTM Geotechnical Testing Journal, Vol. 30 (4), 11 p.
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D5778 − 12 (12) De Ruiter, J. (1982). “The Static Cone Penetration Test: State-ofthe-Art Report,” Proceedings of the Second European Symposium on Penetration Testing, Vol. 2, Amsterdam, 389-405. (13) Lutenegger, A.J. and DeGroot, D.J. (1995), “Techniques for sealing cone penetrometer holes,” Canadian Geotechnical Journal , Vol. 32 (5), 880–891.
(14) Jefferies, M. G., and Davies, M. P. (1993), “Use of the CPTu to Estimate Equivalent SPT N60,” Geotechnical Testing Journal , Vol. 16, No. 4, ASTM, 458–468.
SUMMARY OF CHANGES Committee Committ ee D18 has ide identifi ntified ed the location location of sel selecte ected d cha change ngess to thi thiss tes testt meth method od sin since ce the las lastt issu issue, e, D5778–07 that may impact the use of test method. (Approved January 1, 2012) (1) Added reference to Test Methods D7400 D7400.. electronic onic piezocone (2) Clar Clarific ificatio ation n of defi definit nition ion 3.2.10 electr penetrometer . (3) Added new references and corrected reference numbers in text for these changes. (4) Corrected Eq 8. (5) Corrected definition definition of symbols used in Eq 7, Eq 8, and and Eq Eq 9.
(6 ) Added Note 2 and Note Note 3 and renum renumbered bered subseq subsequent uent notes. (7 ) Added reference to Note 2 in in 13.4 13.4.. (8) Deleted terms hydrostatic pressure, hydrostatic porewater erminology logy D653 in 3.2.10 and pressuree, and reference to Termino pressur 13.5.3.. 13.5.3
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