Behavior of cantilever and geosynthetic-reinforced walls on deformable foundations

A series of plane-strain model tests was performed to investigate the behavior of cantilever soil retaining walls (CWs) and geosynthetic-reinforced soil retaining walls with a rigid facing (GRS-RWs) placed on non-deformable and deformable foundations with various subgrade reaction moduli (k_v). The walls were designed to have configurations similar to those used in practice, with similar controlling safety factors against sliding. Screw jacks and springs were used to simulate undeformable and deformable grounds, respectively, with various maximum foundation settlements of S_max ≒ 0, 2.5, 5, and 10% of the backfill height (H). Test results show that the GRS-RW has better settlement-tolerating performances, in terms of the tilting angle (θ), the horizontal displacement (D_h), and the settlement of the crest of the backfill (D_v1), than those of the CW. For both CWs and GRS-BWs, the worst scenario of the wall performance, in terms of D_h, θ and D_v1, occurred at a moderate foundation settlement of S_max/H ≒ 5% (or k_v = 1.8 kPa/mm), rather than at a greater foundation settlement of S_max/H ≒ 10%, which facilitates a tilting-backward displacement mode. Experimental results also indicate that local lateral pressure coefficients against facing (K_f,z) for CWs may reach the at-rest (or K_o) state at the central portion; values of K_f,z may reach the passive (or K_p) state at the lower portion of the wall. In the case of CWs, the measured values of local and global lateral pressure coefficients (K_f,z and K_f) tend to increase with increasing maximum foundation settlement. This is not the case for GRS-RWs, which exhibited a relatively settlement-independent response, in terms of K_f and K_f,z, against facing. To develop relevant limit-equilibrium-based design methods for CWs and GRS-RWs placed on deformable foundations, knowledge of lateral pressure coefficients associated with various displacement and tilting induced by the foundation settlement are required.