A time-varying critical acceleration framework for an embedded cantilever retaining wall in saturated sand

Accurate prediction of seismic deformation for embedded cantilever retaining walls with saturated backfill remains a critical challenge due to transiently evolving excess pore pressures. This study presents a novel time-varying critical acceleration framework, calibrated against and assessed using a dynamic centrifuge test. Unlike conventional models that assume a fixed resistance threshold, the proposed framework dynamically adjusts the critical acceleration using a softening indicator linked to excess pore pressure ratio, and a recovery indicator reflecting suction-induced strength regain during unloading. Two model variants were developed: a uniform coefficient model and a multi-phase calibrated model with phase-specific softening and recovery coefficients. Implemented through a modified Newmark sliding block approach, the multi-phase model captures both the build-up and the permanent magnitude of measured wall displacement reasonably. Comparison with measured strain time histories along the wall shows that the model reasonably reproduces the internal strain response. An uncertainty analysis using Monte Carlo sampling quantifies sensitivity to the baseline critical acceleration threshold and to softening/recovery coefficients, showing that even modest softening, when repeatedly activated, contributed substantially to wall displacement accumulation, while the recovery mechanism was crucial in mitigating collapse-level deformations. The framework provides a mechanism-based interpretation of complex wall dynamics by explicitly accounting for excess pore pressure driven softening and suction-induced recovery, underscoring their essential role in performance-based seismic evaluation of embedded cantilever retaining walls.