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1. Preliminary Design
1.0. Input data
Design Theme:
The scope of this project is to design a cantilever type of
retaining wall from concrete to create a raisedflat platform. The
backfill is granulal cohesionless soil (sand) with the following
characteristics:
Specific weight:
Internal friction angle:
Cohesion:
19 0.1 Grk
m
3= 18.9
1
m
3k
+31 0.5 uadeg
= 33.5deg
c 0daN
m
2
q =+10 2.5 ua
m
2
22.5
m
2
Surcharge on platform
f 0.44 friction coefficient between base pier and soilpconv 280k
a soil conventional pressure
dH =+3.5 0.1 Nrm 4.3m height of wall above groundheight of wall
under groundtotal height
df 1m
H =+df dH 5.3m
B 3.2m
base width
a =
H
10 0.53m a =Round ,a 0.5m 0.5m wall width
zf =H
80.663
m
zf =Round ,zf 0.05m
0.65m
foot base height
t =max
,
H
2430cm
0.3m
top wall width
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2. Computation of soil thrust (analytical (Rankine) and
graphical (Culmann) method
2.1 Rankine method:
The phrase plastic equilibrium in soil refers to the
conditionwhere every point in a soilmass is on the verge of
failure.
The vertical and horizontal effective principal stresses on
asoil element at a depth z are and respectively. If the'0 'hwall AB
is not allowed to move, then = . The stress'h K0'0condition in the
soil element can be represented by the Mohrscircle a. However, if
the wall AB is allowed to move away fromthe soil mass gradually,
the horizontal principal stress willdecrease.
Ultimately a state will be reached when the stress condition
inthe soil element can be represented by the Mohrs circle b,
thestate of plastic equilibrium and failure of the soil willoccur.
This situation represents Rankines active state, and the
effective pressure on the vertical plane (which is a
principal'aplane) is Rankines active earth pressure.
= for cohesionless soil :kaa
o Soil active pressurecoefficientka =
tan
45deg
2
2
0.289
This method consist in findinggraphically the active pressure
force
exerted by backfiill soil.The reference line line B'C makesangle
with the horizontal plane and
the orientation line is inclined with
angle from the reference line.As the friction between the wall
andsoil is neglected and the back face ofthe wall is vertical the
angle is
taken .
2
Point C is is set at the intersection ofthe reference line and
superior soilsurface. The line BC is divided into 10equal segments
and is computed theweight vectors of each soil triangleGi
represented on reference lineBB'Ciat a convinient scale.Earth
active pressure force vector hasthe direction of the orietation
line, theapplication point in end and theGivertex at the
intersection with .B'Ci
The curve passing to each pressurevector is drawn and the
maximum isfound intersecting a tangent line(parallel to reference
line) and thecurve.
2.2 Culmann method
Pmax =2.88
1.557.82
k
111.014k
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3. Stability checks
Failure scenarios:- sliding (structure beeing to light)-
rotating- sinking (structure beeing to heavy )
Ultimate limit states for:3.1. Sliding3.2. Overturning3.3.
Bearing capacity
3.1. Sliding
=vLFf
Pa Sliding safety factor
Area of wall profile: Aw =+B zf H zf
+t
a t
2
3.94m
2
Total weight of wall: Gw =Aw 25k
m
31m
98.5k
Soil area resting on wall footing:
As =B 2 a H zf 10.23m2
Gs =As 1m 193.347k
Friction force:
Ff =f ++Gw Gs q B 2 a 1m 150.193k
Total soil lateral pressure force:
Pa =H 1m +q ka +q H ka
2
111.068k
vL =Ff
Pa1.352
