Non‐Limit Earth Pressure Behind Foundation Pit Support Structures Under the Drum Deformation Mode

ABSTRACT The finite element elastoplastic analysis method was applied to examine the failure mode and stress deflection characteristics of narrow cohesionless soils behind foundation pit support structures under the drum deformation mode. The mobilized friction angle in the non‐limit state was derived from the quantitative relationship between structural displacement and depth. By introducing soil arching theory and incorporating the stress‐deflected arcuate trajectories of the major and minor principal stresses, earth pressure coefficients for different zones were established. An analytical solution for non‐limit active earth pressure in narrow soils under the drum deformation mode was proposed by improving the horizontal differential element method. The analytical solution showed favorable agreement with finite element simulations, validating the method. Parametric analysis further indicated that the slip surface can be simplified as linear, the support structure requires a horizontal displacement of approximately 0.3% of its height to reach the limit state, and earth pressure varies nonlinearly with depth under the influence of soil arching effect. With increasing displacement, earth pressure transitions from the at‐rest state to the narrow soils state. Furthermore, decreasing the soil width‐to‐depth ratio and increasing either the soil internal friction angle or the interface friction angle were shown to effectively reduce earth pressure on the support structure. These findings contribute to the refinement of the earth pressure theory in narrow soils and provide practical guidance for optimizing the design of support structures.