1815
Technical Committee 205 /
Comité technique 205
3.3 C580 Approach
In the CIRIA C580 design approach, the embedment depth is
determined by achieving equilibrium in a soil-structure
interaction analysis using a pseudo-finite element program
FREW (Oasys 2007).
In the C580 design, partial factors as suggested in “Notes on
Design of excavation and Lateral Support works Using the
Limited State Partial Factor Method” (BD 2005) were adopted
instead to reflect the application of limit state design.
The cantilever bored pile wall is subjected to the unbalanced
loading of slopping ground and hydrostatic pressure. In both
calculations, the pile heads deflections are controlled to be
within 1% of the excavation depth.
4 DESIGN COMPARISION
Two sections are reviewed in this paper: BP11, which is the
closest pile to the existing service reservoir, with retained height
of 18.0 m and BP30, with retained height (deepest excavation)
of 19.4 m.
The results of the deflection and internal structural force for
both of the sections are presented in Figures 5 and 6
respectively.
+159.04mPD
FILL
CDG
M/SDG
CDG
HDG
M/SDG
RS
(PD-(B-C))-R15-G7
Offset 2.7m
Cut-off level
+178.39mPD
30
°
DGWL
+165.53mPD
DGWL
+159.04mPD
FILL
CDG
HDG
Comparison betweenDeflection of BP30
using Traditional Methodand C-580
+130
+135
+140
+145
+150
+155
+160
+165
+170
+175
+180
0
20
40
60
80 100 120 140 160 180
Deflection (mm)
Elevation (mPD)
BP30Traditional
BP30C580
BP30 Traditional
BP30 C580
+159.04mPD
FILL
CDG
M/SDG
CDG
HDG
M/SDG
RS
(PD-(B-C))-R15-G7
Offset 2.7m
Cut-off level
+178.39mPD
30
°
DGWL
+165.53mPD
DGWL
+159.04mPD
FILL
CDG
HDG
Comparison between Bending Moment and Shear
Force of BP30 using Traditional Method and C-580
+130
+135
+140
+145
+150
+155
+160
+165
+170
+175
+180
-20000 -16000 -12000 -8000 -4000 0 4000 8000 12000 16000 20000
BendingMoment (kNm/m)
Elevation (mPD)
-2500 -2000 -1500 -1000 -500 0 500 1000 1500 2000 2500
ShearForce (kN/m)
BP30Traditional,BendindMoment
BP30C580,BendingMoment
BP30Traditional,ShearForce
BP30C580,ShearForce
BP30 Traditional, Bending Moment
BP30 Traditional, Shear Force
BP30 C580, Bending Moment
BP30 C580, Shear Force
+159.4mPD
CDG
HDG
MDG
H/MDG
CDG
HDG
MDG
(PD-(B-C))-R15-G11
Offset -3.6m
Cut-off level
+177.41mPD
28
°
DGWL
+158.4mPD
DGWL
+165.4mPD
CDG
HDG
Comparison betweenDeflection of BP11
usingTraditional Method and C-580
+130
+135
+140
+145
+150
+155
+160
+165
+170
+175
+180
0
20
40
60
80
100
120
140
Deflection (mm)
Elevation (mPD)
BP11Traditional
BP11C580
BP11 Traditional
BP11 C580
Figure 6. Calculated deflection, bending moment and shear force along
cantilever bored pile wall (BP30)
The wall deflection, bending moment, and shear force of the
two methods calculated using FREW at the final stage of the
excavation were compared and summarized in Tables 2 and 3.
Table 2. Comparison of forces in wall and deflection (BP11*)
Embed-
ment
(m)
Bending
Moment
(kN-m/m)
Shear
Force
(kN/m)
Deflection
(mm)
Traditional
Approach
(Geoguide 1)
23.21
8,267
1,041
146.7
C580
20.20
15,710
2,108
146.7
% Change
- 13%
+ 90%
+ 102%
No
Change
+159.4mPD
CDG
HDG
MDG
H/MDG
CDG
HDG
MDG
(PD-(B-C))-R15-G11
Offset -3.6m
Cut-off level
+177.41mPD
28
°
DGWL
+158.4mPD
DGWL
+165.4mPD
CDG
HDG
Comparison between Bending Moment and Shear
Force of BP11 using Traditional Method and C-580
+130
+135
+140
+145
+150
+155
+160
+165
+170
+175
+180
-20000 -16000 -12000 -8000 -4000 0 4000 8000 12000 16000 20000
BendingMoment (kNm/m)
Elevation (mPD)
-2500 -2000 -1500 -1000 -500 0 500 1000 1500 2000 2500
ShearForce (kN/m)
BP11Traditional,BendingMoment
BP11C580,BendingMoment
BP11Traditional,ShearForce
BP11C580,ShearForce
BP11 Traditional, Bending Moment
BP11 Traditional, Shear Force
BP11 C580, Bending Moment
BP11 C580, Shear Force
* BP11 is the closest pile to the existing service reservoir
with retaining height of 18.0m
Fi
ca
gure 5. Calculated deflection, bending moment and shear force along
ntilever bored pile wall (BP11)
