Mechanism and simplified calculation method for landslide thrust distribution under horizontal soil arching between adjacent piles

In landslide stabilization engineering, discretely arranged anti-slide piles establish a continuous resisting surface by mobilizing horizontal soil arching effects between adjacent piles. To elucidate the distribution mechanism of landslide thrust under the inter-pile horizontal soil arching effect and establish a rational calculation method, a finite element analysis was first conducted to investigate the transmission and distribution characteristics of landslide thrust. The results demonstrate that a portion of the landslide thrust continues to propagate into the soil ahead of the arch under the soil arching action. Beyond a critical depth, the load transfer coefficient toward adjacent anti-slide piles stabilizes, indicating a convergence in load redistribution patterns. Subsequently, based on the Mohr-Coulomb strength criterion, the position of the failure surface at the arch foot is determined. Following the principle of prioritizing load distribution to the adjacent anti-slide piles, the height-to-span ratio of the soil arch is established. A calculation method for load transfer coefficient of landslide thrust to the piles under inter-pile horizontal soil arching is then established using the limit equilibrium method. The validity of this method is verified through comparative analysis with results of numerical simulation and model test. Finally, a parametric analysis was performed by selecting the cohesion and internal friction angle of the soil and the pile spacing. The results indicate that when the pile spacing is less than 3 times the pile diameter and the soil cohesion and internal friction angle are sufficiently high, the landslide thrust behind the piles can be considered entirely transferred to the anti-slide piles. The findings provide a theoretical basis for determining the landslide thrust on anti-slide piles, thereby improving the accuracy of pile internal force and deformation analysis as well as the reliability of engineering design.