Design methodology for prestressed locking loads in cable-anchored anti-slide piles under strong seismic excitation conditions

To address the limitations in characterizing pulse effects on anchored piles during near-fault strong earthquakes, as well as the challenges in designing anchor cable prestress loads, this study systematically investigates the structural loading mechanisms, computational approaches, and design methodologies for anchored pile systems through numerical simulations and theoretical analysis. Using the high-cantilever anchored piles at the Ninger Railway Station as a case study, the following key findings were obtained: (1) Near-fault seismic pulse effects exert a pronounced influence on anchor cables, with anchor tension increasing approximately linearly with peak ground acceleration (PGA). Under pulse-type ground motion, the axial forces in anchor cables were found to be 1.4–1.8 times greater than those under non-pulse seismic excitation. (2) By applying the transfer matrix method and incorporating pile–anchor deformation compatibility, a computational approach for anchored pile systems was developed. This method enables the calculation of pile internal forces and deformations under arbitrary external load distributions, as well as the axial forces in anchor cables under quasi-static conditions. (3) A linear relationship was established between the seismic-induced increment in anchor cable tension (ΔT) and the corresponding increment in seismic earth pressure (ΔE) acting on the piles. A theoretical expression was derived for the proportionality coefficient k_i characterizing this correlation. This formulation facilitates the theoretical determination of the locked-in prestress load and supports the development of a simplified seismic design methodology for anchored anti-slide piles. (4) Validation analysis of the station's anchored pile scheme demonstrated that under PGA = 0.45 g, the optimal prestress load is 529 kN, with both anchor tensions and bending moments remaining within allowable limits, permitting pile cross-section optimization to 1.8 m × 2.5 m. For PGA = 0.6 g, prestress loads in the range of 100–302 kN are recommended, with 300 kN as the preferred value. At PGA = 0.9 g, both anchor tensions and pile bending moments exceed design thresholds. Overall, this study proposes a theoretical calculation approach for the tensile force of anchor cables in cable-anchored anti-slide piles under seismic action. A method for determining the upper and lower limits of the prestressed anchor locking load is established, based on the designed tensile capacity of anchor cables and pile stability requirements, thereby simplifying the otherwise complex design process and offering practical guidance for engineering applications.