1. Robust Earth Retaining Wall System to Control
Ground Movement and Minimize Impact on
Adjacent Structures
T.S. Chua, Michelle Lew, V. Rama, H.L. Phua
17. J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D
Diaphragm Walls
Traffic / Canal Diversion
Cross Walls
Decking Works
Excavation & Strutting
Base Slab
Tunnelling Works (West)
ACTIVITY
200820072005 2006
South Dwall
North Dwall North Dwall
Base Slab
Bulk Excavation
Road Diversion
Stage 1A
North Canal
Works
Road Diversion Stage 3
King Posts &
Deck Posts (West)
King Posts &
Deck Posts (North)
Road Diversion Stage 2
King Posts & Deck Posts (South)
Cross Walls
TBM at standstill pending
completion of PPJ base slab
West Drive
(inner bound) West Drive (outer bound)
TBM bore through PPJ
Construction Programme
28. Instrumentation
General Purpose
• To provide necessary information for the design purposes
• To monitor performance during and after construction
• To ensure safety construction (minimise risk & damage)
• To allow less costly construction without danger of failure
Usage
• To monitor the deformation of
- Critical structures, particularly Pasir Panjang Semi Expressway
- Critical utilities: Water Pipes, Telecom, Power Cables and Gas Main
- Ground, including road and sideways settlement
• To measure performance of wall, strut forces and ground water response
Installed Instruments
Optical Prisms Inclinometers Settlement Markers Water Standpipes
Piezometers Strut Monitoring Devices (Strain Gages and Load Cells)
30. Ground Movement near Piers 21-24
during Grout Piles Installation
May – August 2006
PIER INC INCLINOMETER READINGS (mm)
┴ to SITE // to SITE
Towards
SITE
Away fr
SITE
Towards
CITY
Away fr
CITY
P21 IS3001 0 3 0 4.9
P22 IS3002 2.1 0 4.3 0
P23 IS3003 0 6 1 0
P24 IS3006 0 1 0 5
P21 P24P23P22
PPJ SITE
CITY
Grout Piles are used to improve
trench stability during diaphragm
wall construction
31. IS3006 Readings near P24
Displacement during Grouting Works &
Installation of Diaphragm Wall Panels
Panel J17 Panel J18 Panel J19
Grouting Starts
Grouting Ends
Trenching Starts
Casting Ends
IS3006
… 4 mm max
F
M
F1
F1
E
S(IV)
S(III)
32. 0
5
10
15
20
25
30
35
0 5 10
0
5
10
15
20
25
30
35
-5 0 5 10
0
5
10
15
20
25
30
35
0 5 10 15 20
0
5
10
15
20
25
30
35
-15 -10 -5 0 5 10
F
F1
M
E
S(IV)
F
F1
M
S(VI)
S(IV)
Cross Wall
Base Slab
IS3012 IS3002 IW3111 IW3001
Inclinometer Readings
PPSE
Perpendicular to Site
between Piers 22 & 23
As of Oct 08
34. F1
E
F2
S(V)
S(IV)
F
F1
F2
S(VI)-S(V)
S(IV)
GL to S2 EXC
S3 EXC
S4 EXC
S5 EXC
S6 EXC
FEL EXC
S6 REM
S5 REM
M
NORTH SOUTH
IW3117
PPJ-13 PPJ-07
• At shallow depth the soil at south
side is stronger than the soil at
north side
• Preloaded struts
(100-250kN/m) “pushed” the north
wall backwards at shallow depths
• Movement towards excavation
only happened during strut
removals
PL=100kN/m
PL=250kN/m
PL=250kN/m
PL=500kN/m
PL=520kN/m
PL=500kN/m
Ref: Drawing F/856/PPJ/CT/2018B
Base Slab
35. -5
0
5
10
15
20
Displacement,mm
S1 EXC
S2 EXC
S3 EXC
S4 EXC
S5 EXC
S6 EXC
FEL
S6 REM
S5 REM
IW3108
IW3109 IW3110 IW3112 IW3114 IW3116
IW3111IW3117 IW3113 IW3115
North Wall - Max Lateral Displacement Profile
17mm max
