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Singapore, Wen, LTA experience in underground construction
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5/19/2018 Underground Construction Pitfalls to Avoid
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IEAust Singapore 12 Jan 2012 1
Underground Construction
Pitfalls to Avoid
D Wen, BSc, PhDPE, PE(Geo), AC(Geo), CEng, MICE, MIEAust, CPEng
5/19/2018 Underground Construction Pitfalls to Avoid
2/692IEAust Singapore 12 Jan 2012
Soil Investigation & Interpretation
Maintenance
Interfaces Base Stability
Gaps in Retaining Walls
Buildings on Mixed Foundations
Underground Construction - Pitfalls to Avoid
5/19/2018 Underground Construction Pitfalls to Avoid
3/693IEAust Singapore 12 Jan 2012
Soil Investigation & Interpretation
5/19/2018 Underground Construction Pitfalls to Avoid
4/694IEAust Singapore 12 Jan 2012
Soil Investigation & Interpretation
5/19/2018 Underground Construction Pitfalls to Avoid
5/695IEAust Singapore 12 Jan 2012
Interpreted Profile of Surface Wave Velocity
Interpreted Rock Profile
Soil Investigation & Interpretation
5/19/2018 Underground Construction Pitfalls to Avoid
6/696IEAust Singapore 12 Jan 2012
Soil Investigation & Interpretation
5/19/2018 Underground Construction Pitfalls to Avoid
7/697IEAust Singapore 12 Jan 2012
Maintenance
5/19/2018 Underground Construction Pitfalls to Avoid
8/698IEAust Singapore 12 Jan 2012
Maintenance
5/19/2018 Underground Construction Pitfalls to Avoid
9/699IEAust Singapore 12 Jan 2012
Maintenance
5/19/2018 Underground Construction Pitfalls to Avoid
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IEAust Singapore 12 Jan 2012
Maintenance
5/19/2018 Underground Construction Pitfalls to Avoid
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IEAust Singapore 12 Jan 2012
TBM Launching
5/19/2018 Underground Construction Pitfalls to Avoid
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IEAust Singapore 12 Jan 2012
TBM Launching
5/19/2018 Underground Construction Pitfalls to Avoid
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IEAust Singapore 12 Jan 2012
Braddell Road Proposed Depressed Road
TBM Launching
5/19/2018 Underground Construction Pitfalls to Avoid
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IEAust Singapore 12 Jan 2012
F1
30m3 F1 sandsflowing into the
TBM launching
chamber through
the gap between
the TBM shield andthe shotcrete
support of the
launching
chamber.
Road closed foremergency repair.
CPT carried out to
confirm no cavities
under road.
TBM Launching
5/19/2018 Underground Construction Pitfalls to Avoid
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15IEAust Singapore 12 Jan 2012
TBM Launching
5/19/2018 Underground Construction Pitfalls to Avoid
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16IEAust Singapore 12 Jan 2012
TBM Launching or Docking
Ground treatment for TBM launching /
docking: TBM Length + One Ring Length
Quality control of ground treatment
5/19/2018 Underground Construction Pitfalls to Avoid
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17IEAust Singapore 12 Jan 2012
Interface between Stable & Weak Soils
5/19/2018 Underground Construction Pitfalls to Avoid
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18IEAust Singapore 12 Jan 2012
600mm of
settlement
on CTE
due to
DTSS
tunnelling
Interface between Stable & Weak Soils
5/19/2018 Underground Construction Pitfalls to Avoid
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19IEAust Singapore 12 Jan 2012
Weak ground / strong, stable ground
Face pressure governed by overlying
weak ground
Interface between Stable & Weak Soils
5/19/2018 Underground Construction Pitfalls to Avoid
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20IEAust Singapore 12 Jan 2012
IDEALISED PROFILE IN GRANITE
Interface between Rock & Soil
5/19/2018 Underground Construction Pitfalls to Avoid
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21IEAust Singapore 12 Jan 2012
Interface between Rock & Soil
5/19/2018 Underground Construction Pitfalls to Avoid
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22IEAust Singapore 12 Jan 2012
Flushing of the annular gap
Water ingress
Limit of EPB Technology
Coarse granular
material / rocks
Insufficient fines to form
plastic plug
5/19/2018 Underground Construction Pitfalls to Avoid
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23IEAust Singapore 12 Jan 2012
Good EPB Spoil
5/19/2018 Underground Construction Pitfalls to Avoid
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24IEAust Singapore 12 Jan 2012
Difficult to Turn a Mixture of Cut Rock and Granular Spoil into EPB Spoil
May Be Unable to Maintain Target Pressure
Cut Rock & Granular Spoil
5/19/2018 Underground Construction Pitfalls to Avoid
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25IEAust Singapore 12 Jan 2012
Interface between Rock & Soil
5/19/2018 Underground Construction Pitfalls to Avoid
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26IEAust Singapore 12 Jan 2012
Interface between Rock & Soil
5/19/2018 Underground Construction Pitfalls to Avoid
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27IEAust Singapore 12 Jan 2012
Mixed face of strong or very strong rock
with flowing or squeezing soils
Predominantly granular spoil
Need to have high face pressure, but spoil
does not readily form a plug in EPB
machines
Interface between Rock & Soil
5/19/2018 Underground Construction Pitfalls to Avoid
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28IEAust Singapore 12 Jan 2012
Cutterhead Intervention
5/19/2018 Underground Construction Pitfalls to Avoid
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29IEAust Singapore 12 Jan 2012
Over-excavation by Slurry TBM
5/19/2018 Underground Construction Pitfalls to Avoid
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30IEAust Singapore 12 Jan 2012
Feeding Pipe
Discharge Pipe
Flow meterDensity meter
Excavation Management System
5/19/2018 Underground Construction Pitfalls to Avoid
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31IEAust Singapore 12 Jan 2012
Normal Excavation Condition Over Excavation Condition
Excavated
Qty(Cum)
Jack Stroke (m)
Theoretical
Value
Theoretical
Value
Jack Stroke (m)
Excavate
dQty(Cum)
Excavation Management System
5/19/2018 Underground Construction Pitfalls to Avoid
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32IEAust Singapore 12 Jan 2012
Base Stability of Excavation
Hydraulic uplift
D D
Uk1
k2
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33IEAust Singapore 12 Jan 2012
Base Stability of Excavation
Example of hydraulic uplift failure reported by Davies (1984)
Hydraulic uplift
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34IEAust Singapore 12 Jan 2012
Base Stability of Excavation
5/19/2018 Underground Construction Pitfalls to Avoid
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35IEAust Singapore 12 Jan 2012
Shaft Excavation
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36IEAust Singapore 12 Jan 2012
Base Stability of Excavation
5/19/2018 Underground Construction Pitfalls to Avoid
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37IEAust Singapore 12 Jan 2012
Base Stability of Excavation
B St bilit f E ti
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38IEAust Singapore 12 Jan 2012
Base Stability of Excavation
5/19/2018 Underground Construction Pitfalls to Avoid
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39IEAust Singapore 12 Jan 2012
Gaps in Retaining Walls
Soil stability in the gaps
marine clay squeezing through the gaps into
excavation, causing localized soil collapse
Large ground settlements at areas with
gaps in diaphragm walls
Water leaking through the gaps into the
excavation
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40IEAust Singapore 12 Jan 2012
Gaps in Retaining Walls
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41IEAust Singapore 12 Jan 2012
Gaps in Retaining Walls
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42IEAust Singapore 12 Jan 2012
-0
.085
-0
.085
-0
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.085
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.085
-0.07-0.07-0.07-0.07-0.07
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-0.07
-0.065
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-0.06
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06
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6
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-0.045
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-0.035
-0.035
-0.035
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-0.03
-0.03
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-0.03
-0.0
3
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3
-0.03
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3
-0.0
3
-0.03
-0.03
-0.03-0.03
-0.03
-0.025-0.025-0.025-0.025-0.025
.25
.25
.025
.25
.25
-0.025
-0.025
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-0.025
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-0.0
2
-0.0
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2
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-0.015
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5
-0.015
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-0.01-0.01-0.01-0.01-0.01
-0.005-0.005-0.005-0.005-0.005
Gaps in Retaining Walls
G
5/19/2018 Underground Construction Pitfalls to Avoid
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43IEAust Singapore 12 Jan 2012
Ground level
Final excavation level
Underground services
Jet grouted piles to close
the gap in diaphragm wall
Untreated zones below the
service
Diaphragm wall
Gaps in Retaining Walls
G i R i i W ll
5/19/2018 Underground Construction Pitfalls to Avoid
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44IEAust Singapore 12 Jan 2012
Gaps in Retaining Walls
G i R t i i W ll
5/19/2018 Underground Construction Pitfalls to Avoid
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45IEAust Singapore 12 Jan 2012
SandGrouts Gravelcoarse medium fine
Cement
Sodium silicate
Grain size (mm) 2 0.5 0.25 0.074
Groutability Based on Grout
Type vs Soil Particle Size
(after Henn, 1996)
Gaps in Retaining Walls
B ildi Mi d F d ti
5/19/2018 Underground Construction Pitfalls to Avoid
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46IEAust Singapore 12 Jan 2012
UNIFORM
SETTLEMENT
UNIFORM TILT
Building on Mixed Foundations
B ildi Mi d F d ti
5/19/2018 Underground Construction Pitfalls to Avoid
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47IEAust Singapore 12 Jan 2012
Uniform Deformation: Not Damaging
Building on Mixed Foundations
Building on Mixed Foundations
5/19/2018 Underground Construction Pitfalls to Avoid
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48IEAust Singapore 12 Jan 2012
BENDING SHEAR
Damaging Modes of Movement
HORIZONTAL
EXTENSION
Building on Mixed Foundations
Building on Mixed Foundations
5/19/2018 Underground Construction Pitfalls to Avoid
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49IEAust Singapore 12 Jan 2012
Building on Mixed Foundations
Adjacent buildings on different foundations: Old buildings on footings
butted against newer buildings on deep foundations.
Building on Mixed Foundations
5/19/2018 Underground Construction Pitfalls to Avoid
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50IEAust Singapore 12 Jan 2012
Settled by 107mmPiled
Building tilting away fromthe adjacent structure
Building on Mixed Foundations
Building on Mixed Foundations
5/19/2018 Underground Construction Pitfalls to Avoid
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51IEAust Singapore 12 Jan 2012
Building on Mixed Foundations
Building on Mixed Foundations
5/19/2018 Underground Construction Pitfalls to Avoid
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52IEAust Singapore 12 Jan 2012
Annex structure
on footings
abutting buildings
on piles
Building on Mixed Foundations
Building on Mixed Foundations
5/19/2018 Underground Construction Pitfalls to Avoid
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53IEAust Singapore 12 Jan 2012
Building on Mixed Foundations
Main frame on piles, floor slab notsuspended
Building on Mixed Foundations
5/19/2018 Underground Construction Pitfalls to Avoid
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54IEAust Singapore 12 Jan 2012
FILL (6.5m THICK)
SOFT MARINE CLAY
(33m THICK)
SANDY OLD ALLUVIUM
SETTLEMENTBuildings on Mixed
Foundations
Building on Mixed Foundations
Building on Mixed Foundations
5/19/2018 Underground Construction Pitfalls to Avoid
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55IEAust Singapore 12 Jan 2012
Building on Mixed Foundations
Slabs are suspended; columns
not suspended
Building on Mixed Foundations
5/19/2018 Underground Construction Pitfalls to Avoid
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56IEAust Singapore 12 Jan 2012
Walkway - piled
Main load bearing
column - shallow
foundations
Building on Mixed Foundations
Building on Mixed Foundations
5/19/2018 Underground Construction Pitfalls to Avoid
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57IEAust Singapore 12 Jan 2012
Part of the building on piles and part on footings
Damaging at small differential settlements.
Building on Mixed Foundations
Building on Mixed Foundations
5/19/2018 Underground Construction Pitfalls to Avoid
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58IEAust Singapore 12 Jan 2012
Building on Mixed Foundations
Building on Mixed Foundations
5/19/2018 Underground Construction Pitfalls to Avoid
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59IEAust Singapore 12 Jan 2012
Building on Mixed Foundations
Masjid Wak Tanjong
5/19/2018 Underground Construction Pitfalls to Avoid
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60IEAust Singapore 12 Jan 2012
Masjid Wak Tanjong
Building on Mixed Foundations
5/19/2018 Underground Construction Pitfalls to Avoid
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61IEAust Singapore 12 Jan 2012
Fill & Organic clay Weathered Jurong Formation
No 7 No 9
Building on Mixed Foundations
Building on Mixed Foundations
5/19/2018 Underground Construction Pitfalls to Avoid
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62IEAust Singapore 12 Jan 2012
Building on Mixed Foundations
Building on Mixed Foundations
5/19/2018 Underground Construction Pitfalls to Avoid
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63IEAust Singapore 12 Jan 2012
Party Wallto No 9
Shirlaw, Wen, Algeo & Patterson-Kane (2003)
Building on Mixed Foundations
Building on Mixed Foundations
5/19/2018 Underground Construction Pitfalls to Avoid
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64IEAust Singapore 12 Jan 2012
Pocket of soft clay
Building on Mixed Foundations
Oth I ith G d S ttl t
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65IEAust Singapore 12 Jan 2012
Other Issues with Ground Settlement
Oth I ith G d S ttl t
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66IEAust Singapore 12 Jan 2012
Other Issues with Ground Settlement
Do not forget service connections to buildings!
Building on Mixed Foundations
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67IEAust Singapore 12 Jan 2012
To identify buildings on mixed foundations
- A&A drawings
To identify locations of variation in
geology, in particular along terrace houses
A general walk around the site building
inspection
Building on Mixed Foundations
Underground Construction - Pitfalls to Avoid
5/19/2018 Underground Construction Pitfalls to Avoid
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68IEAust Singapore 12 Jan 2012
Soil Investigation & Interpretation Maintenance
Interfaces
Base Stability
Gaps in Retaining Walls
Buildings on Mixed Foundations
Underground Construction - Pitfalls to Avoid
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THANK YOU