Analysis on the effect of pile-raft anti-seismic measures for the tunnel section of weak surrounding rock in strong earthquake area

Abstract

In order to further improve the safety and stability of railway tunnels with weak surrounding rocks during earthquake, the Xinping tunnel at Yumo Railway was taken as an example and, to study the effect of pile-raft seismic measures at the tunnel opening in soft surrounding rocks during strong earthquake using FLAC3D numerical simulation software. The structural displacement and internal force of the two linings without reinforcement were compared, the research results show that the vertical displacement of the pile-arch structure reduced 1.35% and that of the pile-raft-arch structure reduced 1.09%; the side wall convergence of the pile-arch structure has little change (increase 0.44%); due to the better overall stability of the pile-raft-arch structure, the side wall convergence of it is reduced by 30.49%; At the two dangerous sections closest to the entrance of the tunnel, the minimum safety factor of the pile-arch structure has been increased by 1.43% and 6.71%, and the minimum safety factor of the pile-raft-arch structure has been increased by 145.91% and 143.72%; The anti-seismic effect of the pile-raft-arch structure is better than that of the pile-arch structure. It is recommended that the pile-raft-arch structure should better be adopted for seismic reinforcement at the opening section of Xinping tunnel.

Keywords

• tunnel engineering
• weak surrounding rock
• cave section
• pile-arch structure
• pile-raft-arch structure
• seismic stability