Effects of Foundation Excavation on Metro Tunnels at Different Locations and Performance of Corresponding Reinforcement Measures: A Case of Shenzhen Metro Line 11, China

Symmetrical excavation of a foundation pit inevitably causes stress redistribution and deformation in adjacent tunnels, even threatening the safety of their operation. Therefore, it is of practical significance to evaluate the deformation characteristics of adjacent tunnels and propose corresponding reinforcement measures after the excavation of a foundation pit. This study, based on the overlapping tunnel project of the section between Nanshan Station and Qianhaiwan Station of Shenzhen Metro Line 11, analyzes the influence of overlapping foundation pit excavation on adjacent tunnels by numerical simulation method. The deformation characteristics of adjacent tunnels at different locations caused by foundation pit excavation are studied, and the soil reinforcement measures applicable to tunnels at different locations are proposed, respectively. Some useful conclusions have been drawn as follows. The deformation characteristics of adjacent tunnels caused by foundation pit excavation can be divided into three areas: the settlement zone, the transition zone, and the uplift zone. Moreover, for different zones of the tunnel, corresponding soil reinforcement measures are taken, respectively. Soil reinforcement measure makes the soil more monolithic and thus make the stress and strain transfer more uniform, which is effective in reducing soil rebound displacement and tunnel uplift displacement.