Seismic Dynamic Response and Damage Mechanism Analysis of Slope Reinforced by Pile-Anchor Structures

Layered rock slopes are widely distributed in southwest China and are highly susceptible to instability and landslides under seismic loading. Prestressed anchor-anti-sliding pile composite support is one of the most commonly used reinforcement measures, yet its seismic response mechanism is complex, and refined seismic design methods for rock slopes based on damage evolution remain insufficient. To address this, a PLAXIS numerical model of a prestressed anchor-anti-sliding pile composite structure was established for a representative rock slope in Sichuan Province. The seismic response patterns of key parameters, including pile position, length, spacing, and anchor prestress and spacing, were investigated. The HHT-based marginal spectrum method was employed to analyze damage development mechanisms and evaluate the seismic effectiveness of optimized reinforcement layouts. The main findings are as follows. (1) Displacement response analysis indicates that seismic damage is most likely to occur near the upper and lower ends of the sliding surface. Grouting and localized anchorage densification are recommended in these zones. (2) The region around 0.3 L-0.4 L of the anti-slide pile is identified as the seismic damage core zone. Extending pile length and optimizing pile spacing can help reduce the risk of tensile failure in anchors and enhance overall bearing capacity. (3) Anchors are more prone to failure than piles in the combined support system. Increasing prestress improves anchor synergy. A differentiated layout strategy—densifying anchor distribution by 30% in seismic-prone zones and relaxing it in stable areas—can optimize load transfer and reduce slope surface response. (4) Marginal spectrum analysis from an energy-based perspective further confirms the effectiveness of the "localized reinforcement, overall coordination" strategy. This approach suppresses seismic damage near the upper slope and reduces the marginal spectral amplitude by approximately 48%. Therefore, the findings provide theoretical and practical guidance for seismic support design of rock slopes in earthquake-prone regions.