2879
Technical Committee 212 /
Comité technique 212
shown in Fig. 5. The relationship of the Eu/Su and strain level
presented in Fig. 6 is the modulus of soft and stiff Bangkok clay
based on the results of self-boring pressuremeter test during
construction of MRT Subway Blue Line in Bangkok city. Fig. 7
presents deformed mesh of the FEM analysis at the final stage
of excavation at 15.6 m deep.
The result of FEM analysis presents the envelope of lateral
movement of D-wall at final stage of excavation in the order of
28.2 mm. and maximum ground surface settlement of 23.7 mm.
This maximum ground surface settlement behind the D-wall and
lateral movement of the D-wall was set as the trigger level to
control the method of excavation as well as the stability of
Tewavej Palace.
0.3
0.3
0.3
1.0
-19.925m
D-Wall
1.75
+/-0.00
-4.70m
2W350@4m TP1
Lean0.15m
RemoveStrutTP2
StrutTP1
2W400@4m
P4
TP2
TP3
-13.70m
-10.70m
-7.70m
StrutTF1
2W350@4m
TF1
-1.20m
1.3
0
.45
-20.0
DW
Leg pile
-20.0
DW
Leg pile
-20.0
DW
Leg pile
-20.0
DW
Leg pile
-20.0
DW
Leg pile
-20.0
DW
Leg pile
Leg pile
DW
-20.0
F1
-50.0
-50.0
-50.0
-50.0
Layer 5: Dense to
Very dense sand
Layer 4: Medium
to Very dense
sand
Layer 3: Stiff to
Very Stiff Silty
Clay
Layer 2: Soft to
Medeum Clay
Layer 1: Silty Clay
0.00
-50.0
C.L. -1.2
C.L. -7.7
C.L. -13.7
-50.0
F1
P2
P4
F1
P4
P3
P2
P2
F1
F1
-50.0
C.L. -13.7
C.L. -10.7
C.L. -7.7
C.L. -1.2
C.L. -1.2
C.L. -7.7
C.L. -1.2
G.L. -8.1
C.L. -1.2
G.L. -1.75
C.L. -1.2
C.L. -7.7
G.L. -15.2
-50.0
P2
F1
Leg pile
DW
-20.0
P4
P3
P2
P1
-50.0
C.L. -13.7
C.L. -10.7
C.L. -7.7
C.L. -4.7
C.L. -1.2
F1
Leg pile
DW
-20.0
Stage 1
Stage 2 Stage 3 Stage 4 Stage 5 Stage 6 Stage 7 Stage 8
Stage 9
Figure 4. Detail of construction sequences.
Figure 3. Typical section of underground basement.
6 INSTRUMENTATION AND PERFORMANCE OF
DIAPHRAGM WALL
The full set of the instrumentation was proposed to monitor the
behavior of the diaphragm wall and surrounding palaces as
presented in Table 2 and Fig. 2. The results of the piezometer
monitoring by pneumatic type in soft clay was constant with
hydrostatic pore water pressure of ground surface water at 1.00
m. below ground surface.
Table 2. Instrumentation at the Palaces and Diaphragm Wall.
Instrumentation
Location
Purpose
Vibration Sensor
At Tewavej Palace and
Bangkhunphrom Palace.
Vibration at the
palace
Tiltmeter
At Tewavej Palace and
Bangkhunphrom Palace.
Tilt of the palaces
Ground Surface
Settlement point
Ground Surface
Ground Surface
Settlement
Inclinometer
In the Diaphragm Wall
Lateral
D-Wall movement
Piezometer
Outside the D-Wall
Ground water
level
Figure 5. The relationship between modulus and shear strain level
(Mair, 1993).
