Macroscopic Embodiment of Stress–Strain Behavior of Backfill Soil on the Displacement-Dependent Earth Pressure Curve

Treating the soil within the failure zone behind the wall as the specimen in a simple shear box, and the soil transition from initial to limit states as the shearing process of soil specimen, a geometrical model was proposed to describe the relation between wall displacement and soil shear strain. Then, a unified expression for predicting earth pressure as a function of wall displacement from active to passive states was established based on the proposed geometrical model. The core parameters for predicting the displacement-dependent earth pressure curve, namely, the wall displacements at active and passive states, can be obtained by this unified expression according to the stress–strain curves of backfill soil. Additionally, analyses indicate that the initial earth pressure coefficient, the failure zone size behind the wall, and the stress–strain behavior of backfill play a decisive role in the displacement-dependent earth pressure curves. These parameters are responsible for the large wall displacement differences at the limit states among various types of backfill soil and under different densities. More importantly, a reasonable agreement between the proposed model and the experimental results in the literature is obvious.