Bin Liu

Recurrent settlement of high-fill embankments along mountain expressways is difficult to diagnose because its underlying mechanism is often unclear. This study investigates the distressed K610 section of the G76 Xiamen–Chengdu Expressway between Rucheng and Chenzhou by integrating time-series InSAR, ground-settlement monitoring, boreholes, electrical resistivity imaging, ground-penetrating radar, hydrochemistry, engineering records, and three-dimensional finite-element analysis. These data establish a multi-source evidence chain linking deformation, geological structure, hydrological processes, and mechanical response. InSAR-derived line-of-sight velocities range from −30 to −8 mm/yr, and representative points show cumulative displacements of −40 to −50 mm. The anomalous zone extends from the high-fill embankment into the natural slope and spatially coincides with observed settlement, the inferred sliding direction, and radar-detected voids. Groundwater and karst cavities were encountered in 14 and 11 of 39 boreholes, respectively, while three resistivity profiles revealed low-resistivity anomalies beneath the core distressed section, indicating the control of shallow groundwater and karst structures. Water samples from the distressed zone contained an average fluoride concentration of 0.59 mg/L, far below the 17.54 mg/L in the tailings reservoir and similar to mountain surface water, identifying rainfall infiltration as the dominant recharge pathway. Strength-reduction analysis yielded factors of safety of 1.12 under natural conditions and 1.01 under extreme rainfall, a 9.8% decrease; simulated shear-strain concentration zones corresponded closely to field distress. Collectively, the evidence supports a progressive mechanism of rainfall infiltration, water-induced weakening, slope creep, and differential embankment settlement. The framework distinguishes slope-scale creep from localized settlement and supports treatment-boundary delineation and remediation design.

Seismic pier-top pounding in high-speed railway bridges transfers short-duration girder-restraint contact forces into bridge piers, coupling local contact damage with global vibration and possible base yielding. This critical review evaluates how evidence and modelling strategies can be transferred from local contact mechanics to pier response and, ultimately, to whole-bridge seismic demand. The literature is synthesized across experimental and refined numerical characterization, reduced-order contact–structure modelling, response-equivalent-pulse construction, and nonlinear whole-bridge analysis. A qualitative evidence-confidence grading is introduced to distinguish the strength and transferability of the available evidence based on study independence, evidence type, and configuration similarity. The primary scope is high-speed railway bridges, while the underlying contact–structure modelling principles are transferable to conventional railway and highway bridges with comparable pier-top restraints, subject to bridge-specific calibration. Conventional spring-dashpot models are computationally efficient but sensitive to contact stiffness, damping, restitution, and damage assumptions, whereas refined finite-element models resolve local response at substantially greater computational cost. Static, impulse-equivalent, and prescribed pulse representations can reduce analysis effort, but agreement in force or impulse alone does not ensure equivalence in pier displacement, base moment, plastic rotation, or residual demand. Demand-oriented pulses can reproduce selected component-level responses within a calibrated applicability domain, while response-triggered loading remains a conditional system-level reduction requiring reliable event logic, state updating, and independent benchmark validation. Future research should prioritize realistic restraint tests, identifiable parameter ranges, multi-demand validation, uncertainty quantification and damage-updatable repeated-impact models. These advances can provide a mechanics-based basis for performance-oriented restraint assessment, while practical design application requires consistency with code-based seismic restraint provisions and post-earthquake track-system serviceability criteria.