A Generalized Multi-Segment Sliding Wedge Model for Active Earth Pressure Under Narrow Backfill Width

The classical earth pressure theories, such as Coulomb’s and Rankine’s, are derived based on the assumption that the backfill soil extends infinitely behind a retaining wall. However, in many practical engineering situations, the backfill width is limited, and the failure wedge cannot fully develop as assumed in these classical solutions, which leads to inaccuracies in the estimation of the active earth pressure. To address this issue, this study investigates the active earth pressure under a narrow backfill width through numerical simulations and theoretical analysis. A finite element model was developed in PLAXIS 2D to examine the effects of parameters such as the backfill width-to-height ratio and the internal friction angle of the soil on the active earth pressure. Based on the numerical results, a theoretical model was formulated by discretizing the soil into blocks, formulating equilibrium equations for each block, and considering the interactions between adjacent blocks. The distribution and point of application of the active earth pressure were then computed using the finite difference method. Finally, the theoretical predictions were validated through comparisons with numerical results and previous studies.