RETAINING WALL DESIGN
CEGB423 FOUNDATION ENGINEERING
Project on RC Retaining Wall along Kuala LumpurKajang MRT route
Abdul Azim bin Abdul Raji
CE090390
Muhammad Al Hazim bin Yunus CE091967
Maheswaran a/l Salamba Durai CE087554
Introduction
Need to design retaining wall for 100m long
Criteria given:
Inclination due to horizontal = 10
Surcharge pressure = 20kN/m2
Rainy season, water table may rise 2.0m below
original ground level
Material Properties:
Unit weight of backfill (sand), sand = 18 kN/m2
Backfill cohesion, c = 0
Backfill friction angle, = 30
Wall- backfill friction angle, = 0.7
Unit weight of concrete, c = 24 kN/m3
Soil Profile ( from Borehole 1 and 2 )
Soil Profile
Borehole 1 has less total number of blows than
borehole 2, thus taking soil properties from
borehole 1 as consideration.
From SI report and soil profiling, it can be
concluded that Sandy Clay is the soil that
retaining wall need to be constructed on.
No of blows in Sandy Clay soil = 11 blows
clay = 19.64kN/m3
clay = 46.46
C2
= 154 kN/m2
Design Appraisal
Retaining wall height = 5m
Based on textbook page 418, cantilever
retaining wall is only suitable for wall height
more than 8m. Thus, we selected gravity
retaining wall type as design.
Gravity retaining wall depends on their own
weight and any soil resting on the RC for
stability.
Gravity Retaining Wall Dimension
Gravity Retaining Wall Dimension
Gravity Retaining Wall Design
Calculation (checking for FS
overturning)
Properties:
1 = 30
= 10
= 0.71 = 21
= 14
Ka
=
=
= 0.44 < 1 .. O.K !
Continue
Pa
= 1H2Ka
= (18)(5.159)2(0.44)
= 105.4 kN/m
Ph = Pa Cos (10+21)
= 90.35 kN/m
Pv
= Pa Sin (10+21)
= 54.29 kN/m
Continue
Overturning Moment Table:
Area No.
Area (m2)
Weight
Moment
Moment
(kN/m)
Arms (m)
(kN-m/m)
1.245
29.88
1.1
32.78
1.868
44.83
1.85
82.94
0.2075
4.98
0.917
4.567
2.975
71.4
1.75
124.95
Pv=54.29
V=205.38
B=3.5
PvB=190.0
15
=435.252
Continue
Mo
=Ph ()
=90.35(1.7197)
=155.37 kN-m/m
FS overturning
= =
= 2.8 > 2 O.K !
Gravity Retaining Wall Design
Calculation (checking for FS against
sliding)
Properties:
clay
= 19.64kN/m3
clay = 46.46
C2 = 154 kN/m2
Kp
=
= 1.638 > 1 OK!
Continue
Pp
= Kp2D2 + 2C2 D
= (163.83)(19.64)(1.3)2 + 2(154) (1.3)
= 539.63kN/m
FSsliding
=
=
= 11.31 > 1.5 O.K !
Gravity Retaining Wall Design
Calculation (pressure at toe and
heel)
= =
= 0.387 < 0.583 (B/6)
qtoe
=
= 97.61 kN/m2
Continue
qheel
=
=
= 19.75 kN/m2
Cost Calculation
Type
Cost Per Unit
(RM)
Unit Used
Total Cost (RM)
Surveying
General Worker
General Contractor
Consultant Fee
300.00/ site
70.00/ day
90.00/ day
2000.00/ design
1 site
7 days
7 days
1 design
300.00
490.00
630.00
2000.00
629.5 m3
108279.00
629.5 m3
18885.00
12.39 m3
867.00
9.2 m3
230.00
Manpower
Materials
Ready Mix Concrete Grade 30
Normal Mix
Formwork
Backfill Soil
Vegetation
172.00/ cubic
metre
30.00/ cubic
metre
70.00/ cubic
metre
25.00/ cubic
metre
Machinery
Excavator
Loader
Compactor
Bulldozer
Crane
Dump Truck
506.67/
670.00/
536.67/
800.00/
600.00/
693.33/
day
day
day
day
day
day
7
7
7
7
7
7
days
days
days
days
days
days
3546.69
4690.00
3756.69
5600.00
4200.00
4853.31
MISC
Temporary Toilet
130.00/ unit
3 unit
390.00
Cost Calculation
Manpower is based on current general cost in
major construction company
Materials (concrete cost) is based on current
concrete cost according to grade needed
Machinery is based on current machinery cost
by BEM/ IEM costing sheet
Conclusion
Based on the design calculation, all factor of
safety parameters were concluded pass
FS for overturning did not derived far from the
minimum FS value
FS for sliding derived a bit lot from minimum
FS value, making the design pass from sliding
but the cost to build the retaining wall
expensive
The stress at toe and heel is okay because the
stress at toe calculated is larger than the
stress at heel of the retaining wall
