Seismic Active Thrust on Rigid Retaining Wall Using Strain Dependent Dynamic Properties

Abstract

An analytical model is proposed for the evaluation of seismic active thrust on retaining wall resting on sandy soil. Foundation and backfill soil is idealized as Kelvin-Voigt solid. The governing differential equation of vertically propagating shear wave is solved by maintaining the displacement continuity and stress compatibility at the interface between backfill and foundation soil. Nonlinear distribution of accelerations induced in the backfill soil is then used to compute the seismic inertia force. Total seismic active thrust is obtained by solving the force equilibrium equation of the triangular failure wedge. The present method computes the strain-dependent shear-wave velocity and damping ratio of sand from its modulus reduction and damping ratio curves using an iterative scheme. Amplification and deamplification of the input excitations in the foundation soil and backfill soil are compared with results of dynamic centrifuge tests reported in the literature. An increase in the magnitude of seismic active thrust is observed when the retaining wall is situated on sandy soil in place of the rigid stratum, and the percentage increase is 18% in comparison to the latest method available in the literature. The seismic active thrust values for long period input excitations are nearly 13 to 17% higher compared to short-period input excitations. The parametric study reveals that depth of backfill and foundation soil, impedance ratio, amplitude, and frequency of input motion dominate the response of the backfill soil under seismic condition.