Evaluation of the seismic earth pressure for inverted T-shape stiff retaining wall in cohesionless soils via dynamic centrifuge

In the design procedure of a retaining wall, the pseudo-static method has been extensively used and the dynamic earth pressure has been calculated based on force equilibrium using the Mononobe-Okabe method that is an extension of the Coulomb's earth pressure theory. According to the Mononobe-Okabe method, the resultant total dynamic thrust would act at a height of 0.33 H. The Seed and Whitman method that is a modification of the Mononobe-Okabe method, suggests that the dynamic thrust would be applied, at 0.6 H above the base. There is no clear empirical basis for the distribution of the dynamic earth pressure, and recent experimental research studies have shown that the dynamic earth pressure has a triangular shape, and that the dynamic thrust is applied at 0.33 H above the base. Moreover, pseudo-static methods do not consider the effects of the inertial force of the wall itself on the structural behavior. Two dynamic centrifuge tests were designed and conducted to evaluate the magnitude and distribution of the dynamic earth pressure and the inertial effect of the wall itself on an inverted, T-shape, stiff retaining wall with a dry medium sand backfill. Results from two sets of dynamic centrifuge experiments show that the dynamic earth pressure has a triangular shape for critical states during the earthquake, and that the inertial force of the wall significantly influences the structural moment. Moreover, the deformation pattern, the rigidity of the retaining wall, and the frequency contents of the input motions cause the phase difference between the wall and the soil. Correspondingly, this phase difference influences the dynamic earth pressure.