Numerical Simulation Study on the Bearing Characteristics of Rectangular Pile Foundations Under Combined Loading in Slope Topography

Rectangular piles are increasingly utilized in engineering due to their high lateral bearing capacity, which benefits from an adjustable cross-sectional stiffness. However, research on rectangular piles within slope topography remains relatively scarce. Therefore, based on the principle of equal cross-sectional area, this paper establishes four sets of finite element models for rectangular piles with varying aspect ratios to conduct numerical analyses of their bearing characteristics under combined loading at slope angles of 0°, 15°, 20°, and 30°. The results demonstrate that: (1) Under combined loading, the lateral and vertical bearing capacities of rectangular piles interact; as the loading angle increases, the lateral bearing capacity decreases while the vertical bearing capacity increases. (2) Increasing the aspect ratio can significantly enhance the bearing capacity of rectangular piles. Under flat-ground conditions, compared to a pile with an aspect ratio of 1, a rectangular pile with an aspect ratio of 4 exhibits a roughly 75% increase in ultimate lateral bearing capacity and a 15.8% increase in vertical bearing capacity. (3) The critical section of the pile typically occurs within a depth range of 0.28 L to 0.43 L, where its stress mode gradually transitions from predominantly lateral bending and shearing to primarily vertical axial compression. (4) Slopes induce a reduction in the pile’s bearing capacity, but the bearing capacity curve for the pile with an aspect ratio of 4 declines more gently. Thus, rectangular piles with large aspect ratios possess greater engineering applicability in slope topography. This study reveals the bearing mechanism of rectangular piles under the combined influence of the slope weakening effect and the cross-section enhancement effect, providing a methodological reference for the design and application of novel pile foundations in slope terrains.