Dynamic Stability Assessment of Stratified Argillaceous Sandstone Anchorages Under Seismic Load and Dry–Wet Cycles

For the suspension bridge construction located at the site of high seismic intensity, the stability of the anchorage foundation under the seismic load considerably affects the safety of the suspension bridge. Based on a suspension bridge case in southwest China, this study investigated the occurrence of earthquakes in this area and synthesized the artificially designed seismic waves that meet the requirements of the specification. Simultaneously, the FLAC3D numerical model was established, and the dynamic stability of the gravity anchorage foundation system under artificially designed seismic waves was analyzed. The results indicated that under the seismic load, the anchorage foundation system was globally stable, and small sliding and shear damage could be observed on the surface of rock strata. With the seismic load and dry–wet cycles combined, the anchorage foundation’s horizontal displacement and vertical settlement increased, the horizontal displacement was nearly doubled, and the shear plastic zone was enlarged. The grouting reinforcement could strengthen the connection between the anchorage and the surrounding rock strata, reducing the surrounding rock strata’s dynamic shear strain, particularly from 6 × 10⁻³ to 2.5 × 10⁻⁴ at the midsection of the slope. The safety factor at the base of the foundation pit fluctuated around 1.0 before reinforcement, increasing to greater than 2.5 after reinforcement.