This study presents a pseudo-static analytical solution for evaluating seismic active earth pressure acting on retaining walls with narrow cohesive backfill adjacent to a rock face under rotation about the base (RB) mode. Finite element limit analysis (FELA) using OptumG2 is employed to investigate failure mechanisms for different width-to-height ratios, revealing that the slip surface evolves from a composite form consisting of a logarithmic spiral and a straight line to a single logarithmic spiral as the backfill width decreases. Based on these observations, an analytical model is developed using the horizontal differential element method, in which soil arching is incorporated through stress deflection angles and the trajectory of the minor principal stress. Parametric analysis indicates that increasing wall–soil interface friction and rock slope inclination can significantly reduce the active earth pressure coefficient, while horizontal and vertical seismic accelerations exert opposite effects. Comparisons with FELA results and existing theoretical solutions demonstrate good agreement and show that the proposed method predicts lower and more realistic earth pressures for narrow backfill under RB mode. The proposed framework provides a practical and reliable tool for the seismic design of retaining walls under constrained backfill conditions.
Zhu et al. (Wed,) studied this question.