Demand-Oriented Spatial Reinforcement Design of Circular Anti-Slide Piles for Enhanced Structural Performance and Reinforcement Reduction

A demand-oriented spatial reinforcement scheme was developed for circular anti-slide piles subjected to a known dominant direction of landslide thrust. Based on the depth-dependent bending-moment and shear-force demands, the proposed scheme integrates uniformly distributed full-length base bars, supplementary longitudinal reinforcement concentrated within the principal tension sector, depth-dependent termination of longitudinal bars, and variable-pitch spiral reinforcement. A three-dimensional nonlinear finite-element model was established to compare the proposed scheme with a conventional circumferentially uniform reinforcement arrangement under identical geometrical, material, loading, and boundary conditions. The results showed that the proposed scheme reduced the total reinforcement volume from 1.243 to 1.041 m3, corresponding to a reduction of 16.3%. At 40% of the design load, the pile-head displacement increased slightly by 3.96%, indicating a minor reduction in initial stiffness. Under the full design load, however, the pile-head displacement, maximum longitudinal-bar stress, and maximum equivalent plastic strain decreased by 5.48%, 15.7%, and 34.5%, respectively. The concrete damage distribution also became more localized and discontinuous near the critical region. These results demonstrate that demand-oriented spatial reinforcement can improve reinforcement utilization, reduce local response concentration, and enhance deformation control under high load levels while achieving substantial steel savings.