Formulation of Seismic Passive Resistance of Retaining Wall Backfilled with c-F Soil

Formulation of Seismic Passive Resistance of Retaining Wall Backfilled with c-F Soil

Sima Ghosh (National Institute of Technology Agartala, India)
Copyright: © 2012 |Pages: 10
DOI: 10.4018/jgee.2012070102
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Abstract

Knowledge of passive resistance is extremely important and it is the basic data required for the design of geotechnical structures like the retaining wall moving towards the backfill, the foundations, the anchors etc. An attempt is made to develop a formulation for the evolution of seismic passive resistance of a retaining wall supporting c-F backfill using pseudo-static method. Considering a planar rupture surface, the formulation is developed in such a way so that a single critical wedge surface is generated. The variation of seismic passive earth pressure coefficient are studied for wide range of variation of parameters like angle of internal friction, angle of wall friction, cohesion, adhesion, surcharge, unit weight of the backfill material, height and seismic coefficients.
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2. Method Of Analysis For Seismic Passive Resistance

Consider a rigid retaining wall of height H supporting c-Φ backfill of unit weight γ, the planar triangular wedge surface ABD of which is inclined at an angle θ with the vertical. If ca is the unit adhesion, c is the unit cohesion, δ is the angle of wall friction, kh and kv are the seismic acceleration coefficients then the forces acting on the wedge surface during passive state of equilibrium are shown in Figure 1. Pp and R are the passive resistance and reactive force due to retained backfill respectively.

Figure 1.

Forces acting on retaining wall – soil wedge system during passive state of equilibrium

Applying the force equilibrium conditions, ∑H = 0 and ∑V = 0,

(1)
(2)

Solving Equation 1 and 2 and putting W = (γH2tanθ)/2, Q=qHtanθ, C = cH secθ, Ca = caH, ψ = tan-1(kh/(1±kv)) we get Equation 3, shown in Box 1.

Table 1.
Comparison of the results obtained from the present study with Subba Rao and Choudhury'2005 [Φ = 30°, δ = Φ/2, kh = 0.3, c = 8 kN/m2, ca = 6 kN/m2, q = 15 kN/m, γ = 18 kN/m3]
Conditionkv Subba Rao and Choudhury (2005) (Pp in kN/m)Present study (PP in kN/m)
c-Φ soil with surcharge04457.464461.49
0.31983.781998.28
c-Φ soil without surcharge03893.573912.14
0.31759.431777.13
Φ soil with surcharge03847.583853.39
0.31536.741547.93

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