Centrifuge shaking table tests on tiered reinforced soil retaining walls subjected to the excitations of near-field ground motions

Tiered geosynthetic-reinforced soil (GRS) retaining walls are becoming increasingly popular in earthquake-prone areas due to their excellent earthquake resistance. Typically, near-field strong ground motion is characterized by a significant vertical component and/or a long-period velocity pulse. However, this is seldom considered in the current design of tiered GRS walls. In this study, two centrifuge shaking table tests were conducted to investigate the earthquake performance of tiered GRS walls under bidirectional and pulse-like excitations. The results revealed that under bidirectional excitation, the wall model underwent significant deformation. The confining pressures in the soil increased due to vertical motion, resulting in notable changes in the shear modulus of the backfill. Due to large differential settlement and vertical excitation, the earth pressures were significantly impacted. In the second case, pulse-like motions induced considerable shear strains in the backfill, leading to significant alterations of the shear modulus and dynamic damping of the structure. The facing exhibited distinct deformation modes, with some sliding at the toe. The peak wall displacement and reinforcement strain were both notably higher than the residual values. However, in both cases, the connections between the reinforcements and the facing endured relatively large strains, and need to be considered in seismic design.