Ground Improvement

Symposium on Innovation and Challenges in Asian Tunneling SICAT 2017 7 & 8 September 2017

By

Er.. Dr Er Dr.. Chew Chew Soon Soon Hoe Assistant Professor, National University of Singapore of Singapore Council Member – Member – Institute of Engineers, of Engineers, Singapore (IES) President, Singapore Chapter of ASCE of ASCE

Prof. CHEW SH (NUS)

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FOCUS of of THIS THIS PAPER • Singapore is small in size (a small red

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and yet see a wide variation of soil/rock of soil/rock profile.

• It ranges from “thick layer of very of very soft clays” to “fractured hard rock”, as well as “mixture of soft of soft soils and hard rock within the same tunnelling face” (so called “mixed soil” condition). • In many station construction and tunnelling works associated with MRT and HSR construction, some of these of these soil/rock profiles encountered will need some form of improvement or treatment for : (a) construction safety, (b) limiting ground movement, (c) limiting water seepage, (d) limiting ground lost, (e) Prof. CHEW SH (NU S) better construction rate and better productivity.

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FOCUS of of THIS THIS PAPER of various traditional ground improvement • The principle of various techniques are available for various type of soil of soil profiles to satisfy various design criterion.  Yet,

innovative application and/or careful modification modification are needed to implement at site for the project to be successful. of these improvement • This papers will discuss some of these techniques and their innovative implementation with reference to Singapore contact. Special reference will be paid on the proposed HSR station at Jurong East and the proposed tunnel towards Tuas. Prof. CHEW SH (NUS)

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1. Introduction Introduction of of SG SG‐KL HSR project  Singapore side 2. History and Geology of Jurong of Jurong East Site 3. Geotechnical Challenges Challenges – – Geotechnical Geotechnical Condition at Jurong East Area, Singapore Formation – including limestone cavity ‐‐ Jurong Formation – Formation – Soft clay, Peaty Soil and F1 Sand ‐‐ Kallang Formation – 4. Challenges 4. Challenges in Vertical shaft and tunneling works 5. Ground Improvement Techniques for Confronting above Challenges – Grouting, Suitable Chemical and continuous progressive soil investigation while tunneling etc 6. Conclusion Prof. CHEW SH (NUS)

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FOCUS of of THIS THIS PAPER of various traditional ground improvement • The principle of various techniques are available for various type of soil of soil profiles to satisfy various design criterion.  Yet,

innovative application and/or careful modification modification are needed to implement at site for the project to be successful. of these improvement • This papers will discuss some of these techniques and their innovative implementation with reference to Singapore contact. Special reference will be paid on the proposed HSR station at Jurong East and the proposed tunnel towards Tuas. Prof. CHEW SH (NUS)

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1. Introduction Introduction of of SG SG‐KL HSR project  Singapore side 2. History and Geology of Jurong of Jurong East Site 3. Geotechnical Challenges Challenges – – Geotechnical Geotechnical Condition at Jurong East Area, Singapore Formation – including limestone cavity ‐‐ Jurong Formation – Formation – Soft clay, Peaty Soil and F1 Sand ‐‐ Kallang Formation – 4. Challenges 4. Challenges in Vertical shaft and tunneling works 5. Ground Improvement Techniques for Confronting above Challenges – Grouting, Suitable Chemical and continuous progressive soil investigation while tunneling etc 6. Conclusion Prof. CHEW SH (NUS)

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[Channel NewsAsia, 19 Jul 2016] A Memorandum of Understanding of Understanding (MoU) on the Singapore ‐Malaysia High‐Speed Rail (HSR) project was signed on 19 July 2016. It is expected to reduce travel time between Singapore and Kuala Lumpur to around 90 minutes. Prof. CHEW SH (NUS)

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Key Facts Total Length

350km

Number of Stations

8

Operating Speed

300km/h

Train

10 car train

Number of Services

3

Express International

KL‐SG

Shuttle International

KL‐SG

Domestic Service

Malaysia only

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This is in line with plans to transform Jurong East into Singapore's second Central Business District Prof. CHEW SH (NUS)

[The Straits Times, 6 May 2015]

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[Straits Times, 12 May 2015]

The Jurong Country Club, which was founded in 1975, has a land lease for the site until 2035. The club completed an 18‐hole renovation in July 2012, which about $24 million. Prof. CHEW cost SH (NUS)

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• located within the 67 hectares of plot currently occupied by the Jurong Country Club. • Land for the terminal = 13 hectares. • The remaining 54 ha will be comprehensively developed into “Jurong Lake District” ‐ include office space, hotels, retail and entertainment facilities.

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Tunnel

15km

• Tunnel lilely below AYE • Total Length = 15km

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Jurong Country Club

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One Artist Impression – for illustration only Shopping ,Roof Garden

Carpark

Shopping Area, F & B

Drop off area, coach area, shops

Custom, ticketing etc

Arrival & Departure

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2. History and Geology of Jurong East Site

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Location with Geological Outcrop

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Location with Geological Outcrop

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• Before large‐scale development, the Jurong Country Club site, which is seated around Sungei Jurong, Jurong lake and Sungei Pandan area, used to occupied by mangrove forests with an outer line of mud and sand.

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Water Channel

In the Year of 1872 Prof. CHEW SH (NUS)

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Peng Kang

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Mangrove Forest Area

In the Year of 1911

Pandan

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1954

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1972

1961

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Golf course built Water channel shape formed

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In the Year of 1975

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Landfill to divert water channel

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In the Year of 1984

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Jurong country clubhouse was still a single storey building

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In the Year of 1995

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Jurong country clubhouse reconstructed Man‐made water feature

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In the Year of 2007

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Proposed HSR Terminal

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In the Year of 2017

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[NewLaunch101, 11 May 2015]

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[Straits Times, 14th May 2015]

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[The Business Times, 13 May 2015]

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Geology of Singapore – DSTA, 2009

Kallang Formation

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Jurong Formation

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Geology of Singapore of Singapore – – DSTA, DSTA, 2009 Kallang Formation, Alluvial member (Ka)

Jurong Formation, Tengah Facies (Jt) Ayer Chawan Facies (Jac) Queenstown Facies(Jq)

Kallang Formation

Jurong Formation

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Central Belt Eastern Belt Prof. CHEW SH (NUS)

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‘recent deposits’ (Scrivenor, 1924)

‘Recent Alluvium and related deposits’ (Alexander, 1950)

5 members recognized (DSTA, 2009)

• Alluvial Member (Ka): of the Kallang and Jurong • valley fills & thin veneer on the floor of the River basins vary – pebble beds through sand, muddy sand, and • deposits vary – clay to peat •  Locally we call it F1 ‐‐ Loose sand and E – Estuary Peaty soil • Prof. CHEW SH (NUS)

‘Shale & Sandstone’ (Scrivenor, 1924)

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‘Older Sedimentary Rocks’ (Alexander, 1950)

Presence of limestone (since 1987)

Jurong Formation with 7 Facies (DSTA, 2009)

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• Ayer Chawan Facies (Jac) • Well‐bedded tuffaceous muddy sandstone & mudstone

• Tengah Facies (Jt) • muddy fine to medium grained poorly lithified sandstone • weathered material that has developed in‐ situ, possibly in marine environment

• Queenstown Facies(Jq) • consists predominantly of thinly of thinly bedded red and purple mudstone mudstone with some red to purple shale

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Inferred fault Thrust fault Strike/dip Syncline Anticline

Project is located within 2 inferred faults (NE‐SW) and 1 thrust fault (NW‐SE)

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Expected Fault Types Within Project Area Thrust Fault: Reserve fault in respond to compressional forces by pushing up a rock block over the other – Murai Thrust fault, DSTA, 2009 Rock around this fault line, tends to be Schist/slate and easier to break into sheet like

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Mudstone = Schist/Slate

Tends be a weak zone and slide along the cleavage / easier to be broken into sheets

Low angle thrust, close to horizontal, but the Fault zone (highly fractured zone) will be shallower and conceptually rock quality in hanging wall will be poorer than footwall Mudstone been pressed – cleavage parallel to sub‐ parallel to bedding

Tear Fault : Fault occurring in the rocks above a low‐angle thrust fault and striking approximately at right angles to the strike of the low angle thrust fault. The rock blocks are displaced horizontally. Tear fault normally cut vertically.

Flower structure is expected to encountered.

Northeasterly trending fault in Jurong Formation are considered to be tear fault, (DSTA 2009)

Normal faults

Normal faults due to tran‐tension

What about Limestone??

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Litho‐stratigraphy of Jurong Formation

Dark grey Limestone, Pandan Facies, fossils can be observed, NUS, near to Sport Drive, Ayer Rajah Expressway Source: Geology of Singapore, 2nd edition, DSTA, 2009

Reef ? Fossil

Colonial coral (?) in growth position but distorted

Brachiopods fossil

Site investigation borehole data from Jurong West N1 C29/C32 project

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• Borehole depth varies from 40m to 67m

Typical soil profile from adjacent site development.

• 4 distinct layers – Fill, Organic clay (E), Residual Soil (SVI), Completely weathered Sedimentary Rock (SV)

• Possible cavities found at depth from 26.5m to 40m. Prof. CHEW SH (NUS)

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Yung Ho Rd Proposed site Tukang Innovation Drive

Penjuru Rd

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All adjacent site reference borelogs show similar soil profile: Fill > KF > JF (S‐VI, S‐V) No bedrock were found up to 67m depth.

Show possible limestone formation

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Cavity – possible Borehole 4 Borehole 7 & 8

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Cavity ‐‐ need to identify and treat them..

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For Illustration only

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Jurong Lake Garden Area Proposed site

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N=0

12m

M 15m

N=0

M

N=0

N=0‐14

N=9

RL88.4

E 15m

F2 RL85.5

N=16

N=9‐12

N=10‐12

RL85.3 N=16

S(VI) silty sand

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1.5m

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1m bgl N=4 N=2

1m bgl FILL 3m N=2

M

15m

F2 N=5‐17 RL83.4

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N=9

N=2

E 16.5m

3m

RL83.7 S(VI) Silty sand N=18‐22

1.5m

10.5m M

1m bgl

N=2‐4

15m N=3‐8

RL89.3 N=9‐16

RL83.5 N=27 N=23

S(V) N=100 Silty sand

S(VI) Silty sand

N=100

sandstone

N=5‐12

N=100

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BH1

BH5

BH7 BH11 BH31

~300m Prof. CHEW SH (NUS)

BH1 RL104.12 1.5m

1m bgl

8181

BH5 RL104.24

BH7 RL104.4 1.5m

BH11 RL104.44 1m bgl 1.5m

BH31 RL104.59 1.5m

24m 34m 34.5m

27.5m

38.5m

RL75.6

[Cross‐Section BH1‐BH5‐BH7‐BH11‐BH31] Subsoil lies within the geological demarcation of Jurong Formation. Widely distributed with thick layers of sandy clay, sandy silt, clayey sand and silty sands soils) Prof. CHEW SH(residual (NUS)

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BH1

BH3

2m bgl N=4‐7 8.3m

RL89.4 3.3m

2m bgl

Fill 2.4m bgl RL74.9 7.4m N=4‐11 Silty Clay with Sand 9.6m

N=4 8.8m N=6‐8

N=100

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BH2

14.4m

N=4‐6

N=7‐8

Clayey Silt N=33‐47

N=59‐100

Clayey Silt with Sand N=81‐100

[Cross‐Section BH1‐BH3‐BH2]

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2‐3 Floors Basements

E

D

C

Reference Soil Profile (SI report of Jurong East RC1)

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Reference Soil Profile (SI report of Jurong Lake) Prof. CHEW SH (NUS)

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3. Geotechnical Challenges – and Comforting Geotechnical Condition at Jurong East Area, Singapore

‐‐ Jurong Formation ‐‐ Kallang Formation – Soft clay and Peaty Soil

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1. Highly varied in soil/rock profile at this site 2. Present of peaty soft soils  long term Settlement to be considered 3. Discontinuous layers 4. Presence of cavities / underground streams 5. Mixed phase soil/rock may be encountered when tunnelling Prof. CHEW SH (NUS)

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Highly varied soil profile

Geological Cross Section A‐A Site 5

Jurong Country Club

Site 3

0m Sandy Silt (FILL) SPT N = 9

6m 9m

Very Sot Clay (KALLANG FORMATION) SPT N = 0‐2

Firm Sandy Silt (JURONG FORMATION) SPT N = 2

26m

Sandy Silt (FILL) SPT N=16

Sandy Silt (FILL)

Sandy Silt (JURONG FORMATION S‐V) SPT N=31‐37

KALLANG FORMATION Soft Clay JURONG FORMATION Sandy Silt/Clay Cavity

Sandy Silt (JURONG FORMATION S‐V) SPT N=67 Sandy Silt (JURONG FORMATION S‐V) SPT N=100

JURONG FORMATION Sandy Silt

Cavity

30m 36m 40m 46m

Weak to moderately Strong Sandstone (JURONG FORMATION S‐III) SPT N=100

Sandy Clay (JURONG FORMATION SPT N = 3 Hard Silt (JURONG FORMATION) SPT N = 30 Hard Silt (JURONG FORMATION) SPT N = 100

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0m 3.5m

8.1m 10m 15m

30m

JURONG FORMATION Sandstone

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Problem with Jurong Formation Bedrock profile

Features of Jurong Formation: Limestone interbedded with mudstone, siltstone and sandstone

Steeply inclined bedding planes

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Top of rock level is undulating – Need for closer boreholes spacing

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Piles cannot rest on Mudstone – easily soften with water

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Limestone karstic feature – may need ground improvement

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Problem with Kallang Formation – Thick soft soils

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Problem with Kallang Formation – Thick soft soils

FILL PEAT S(IV) JF (V. SOFT)

S(V) JF (HARD) CAVITIES

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Problem with Kallang Formation – Soft soils

Soft soil –

‐‐ will give rise to excessive settlement issue. Peaty soils in particular ‐‐ High secondary consolidation settlement ‐‐ will continue to settle over many many years without increase in load.

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Problem in tunneling in mixed soils condition Classification of Mixed Ground A mixed ground is usually defined as occurrence at excavation face of two or more type of soils with significantly different properties that affect TBM operation. They can be: (a) Layered or banded ground formed by rock beddings, dykes, faults or shear zones. (b) Interface ground of soil and rock, typically weathered materials above bedrock. (c) Mixed ground with locked corestones mixed with soil materials. Prof. CHEW SH (NUS)

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Problem in tunneling in mixed soils condition Classification of Mixed Ground

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Problem in tunneling in mixed soils condition In Jurong

Tuas Area

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Problem in tunneling in mixed soils condition In Jurong

Tuas Area

‐‐ > Tunnelling in these varied soil profile has to be carefully planned..

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Problem in encountering limestone

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4. Challenges in vertical shaft and tunneling works

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Next, let me summarize some

Challenges in Vertical Shaft/Station Box Vertical Shaft ‐‐ for Launching shaft and receiving shaft as well as Station Box construction

Challenges in Tunneling works

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Challenges in Vertical Shaft/Station Box

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Challenges in Vertical Shaft/Station Box

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5. Ground Improvement needed to confront the geotechnical issues above

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Here, We have to consider the following two structures:

• Vertical Shaft ‐‐ for Launching shaft and receiving shaft as well as Station Box construction ‐‐ Earth retaining structure needed. • Tunneling In the above mentioned difficult ground conditions. Prof. CHEW SH (NUS)

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Vertical Shaft / Station Box Due to present of thick soft soil, and the closed proximity to neighbor high‐rise building, the retaining structure has to be rigid and strong.. Typical using Contiguous bored piles or secant pile wall or Diaphragm wall.. Need many layers of struts or internal JGPs strut.

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Vertical Shaft / Station Box

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Vertical Shaft / Station Box Diaphragm wall

Anchoring

Strutting

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General Ground Improvement Methods

Ground improvement methods Not suitable here

Mechanical Modification Methods

Compaction

Hydraulic Modification

Vertical Drains

(Source: Hayward Baker) Prof. CHEW SH (NUS)

Physical & Chemical Modifications

Grouting, )DCM r e k a B d r a w y a H : e c r u o S (

(Stapelfeldt, 2006) 130

Cement treatment methods Ground Improvement Methods

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Cement treatment methods Ground Improvement Methods

Jet Grouting

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Jet Grouting “Jet”

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Compaction grouting Ground Improvement Methods Application of Compaction grouting


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Settlement control by Compaction grouting

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Cavity filling by Compaction grouting


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Cavity filling by Compaction grouting


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Jet Grouting – Types


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Jet Grouting – Super Large diameter

Or other equivalent products – e.g. SuperJet etc

Minimum diameter is 4.2m and the maximum 139 Prof. CHEW SH (NUS) is 5.0m. diameter

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Jet Grouting – Super Large diameter Need it in corners with full of underground services • SonicJet columns constructed to form into a retaining wall, for the closing of the gap.

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Jet Grouting – Super Large diameter Need it in corners with full of underground services • SonicJet columns constructed to form into a retaining wall, for the closing of the gap.

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Jet Grouting – Super Large diameter Need it in corners

The diameter was determined -- the minimum Prof. CHEW SH (NUS) diameter is 4.2m and the maximum diameter is 5.0m.

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Icsge 2015 – “large diameter sonicjet pile”, Chew et al

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Icsge 2015 – “large diameter sonicjet pile”, Chew et al

Icsge 2015 – “large diameter ”

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Movement at 3 m away form SonicJet < 3mm

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Tunneling in Soft Soil Ground • Tunneling in Soft soils in highly build‐up area will cause excessive ground settlement issues.. • Soft ground needed to be treated – Commonly using Jet Grouting or DCM • Sometime, grouting has to be done at the congested area with limited ground surface available. 

Inclined grouting  super large diameter JGPs Prof. CHEW SH (NUS)

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Tunneling in Mixed Soil Condition Solution for Mixed Soil Tunneling Either Option A. Make TBM machine to ‘s uit ’ the ground. Convertible TBM Or Option B . Ground tr eatment (improvement) to make the ground to ‘s uit’ the machine. Prof. CHEW SH (NUS)

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Tunneling in Mixed Soil Condition Option A. Make TBM machine to ‘suit’ the gro und.

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Tunneling in Mixed Soil Condition Option A. Make TBM machine to ‘suit’ the gro und.

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Tunneling in Mixed Soil Condition Option A. Make TBM machine to ‘sui t’ the gro und.

What are the Challenges ?

• Timely characterization of soil and weathered rocks as the tunnel progresses.. • Possible exploration by geophysical methods above ground or probing ahead of tunnel face • How to measure and model mixed face behaviour?

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Tunneling in Mixed Soil Condition Option B. Ground t reatment (imp rovement) to make the groun d to ‘s uit’ the machine. • Condi tioning of t he grades S(III/IV) and S(V) materials: Use  make gr ade S(III/IV) with less p ermeable Permeation Grouting  and make grade S(V) more stable. Use Jet Grouting/DCM • Temporarily lowering down ground water table to reduce water pressure and water infl ow. • Watch out for sand lenses – use TAM Grouting/Chemical Grouting Prof. CHEW SH (NUS)

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Tunneling in Mixed Soil Condition Option B. Ground t reatment (imp rovement) to make the groun d to ‘s uit’ the machine. • Tunnel face can also inj ect special flui d to “ condit ion the soil” ahead of cutting or during cutting. use of special cement+ bentonite + chemical mi x.. • Function:

-- dispersed the clay to reduce plastici ty -- harden faster -- better flow c haracteristic f or easy excavating.

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Tunneling in Mixed Soil Condition

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Ground Improvement

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