Article Preview
Top2. 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]
| Condition | kv |
Subba Rao and Choudhury (2005) (Pp in kN/m) | Present study (PP in kN/m) |
| c-Φ soil with surcharge | 0 | 4457.46 | 4461.49 |
| 0.3 | 1983.78 | 1998.28 |
| c-Φ soil without surcharge | 0 | 3893.57 | 3912.14 |
| 0.3 | 1759.43 | 1777.13 |
| Φ soil with surcharge | 0 | 3847.58 | 3853.39 |
| 0.3 | 1536.74 | 1547.93 |