Discrete element analysis of horizontal soil arching effect in pile-supported retaining structures

Abstract This study focuses on the evolution of horizontal soil arching effects during the excavation of pile-supported retaining structures through the Discrete Element Method (DEM) using Particle Flow Code 2D (PFC2D). In the DEM model, square wall elements are constructed to simulate square piles, representing the horizontal cross-section of an excavation. The horizontal soil arching effect induced by excavation under varying parametric conditions was investigated. The results indicate that the soil arching effect progressively evolves through three characteristic stages during excavation — compaction, load transfer, degradation, and failure. The lateral earth pressure on the pile initially increases rapidly, followed by periodic fluctuations as excavation depth increases. When the wall displacement ratio exceeds 2.25%, the soil arching effect and support efficiency begin to decline, and when it surpasses 4%, the bearing capacity of the pile-supported retaining structures significantly deteriorates. By simulating the pile response under various net pile spacings, the study determines that an optimal net pile spacing of 1.5 to 2 times the square pile width maximizes the soil arching effect while enhancing pile-bearing capacity. These findings provide essential theoretical insights and technical guidance for the design of excavation support systems.