Slope stability analysis and protection measures in bridge and tunnel engineering: a practical case study from Southwestern China

This study addresses the instability problem of typical slopes in the engineering constructions of bridges and tunnels in Southwestern China by combining the results of detailed field monitoring, geological and geometrical investigation, and numerical simulations and then proposes comprehensive protection measures. The study area is a vital part of the Chengdu–Lanzhou high-speed railway in Sichuan Province, located in the 5·12 Wenchuan’s meizoseismic area. The slope stability was analysed based on the data collected by field monitoring. The results indicated that the slope toe was stable under a natural state, while a large deformation was observed occasionally owing to tunnel blasting and excavation. Subsequently, a digital binocular camera installed on a fixed-wing unmanned aerial vehicle was used to identify unstable rockmass. By analysing the slope and the dip direction angles, three potential paths of rockfall hazard were selected for further studies. A retaining wall and a soft protecting net were installed along the slope to intercept potential debris flow and possible falling rocks above the tunnel portal, respectively. A Mohr–Coulomb model was built using universal distinct element code to identify the rockfall initiation position. Overall, the field monitoring results were in good agreement with those obtained by numerical simulations. Moreover, the Rocscience Rocfall program was used to calculate the bounce height and the total kinetic energy of falling rocks. Finally, mitigation measures for the potential landslide, rockfall, and mudslide hazard were proposed and adopted in practical engineering applications, and aimed to provide a useful reference for similar engineering practices.