Safety Analysis of Shield Tunnel Due to Vibration of Metro Operation

摘要

This paper concerns the safety of shield tunnel lining structure and adjacent weak stratum during metro operating. By considering the joints, the A-B-K segments and the weak stratum, numerical simulations were performed for dynamic response safety of shield tunnel buried in thick soft soil under vibrating load of metro train in Guangzhou in detail based on an elastoplastic three-dimensional dynamic finite difference modelling. Results of numerical simulations show that metro operating induces significant dynamic response in segments and adjacent weak stratum. The severe dynamic response zones of lining structure mainly distribute in the range of lower half of segment-ring. In two horizontally symmetrical corresponding positions of segments lining, dynamic response of the one approaching to joint is severer than that of the one apart from joint. The nearer the zone of foundation soil is to lower half of segment-ring, the severer the response is. The zone which presents maximal shear strain rate in foundation soil locates near the joint between two normal segments at bottom. The dynamic response of stratum is damped quickly from tunnel wall to deep stratum. The obviously vibrated zones of stratum mainly distribute in the range of about two times the tunnel dimension from tunnel axis. Under long time cyclic vibrating load induced by metro train, it is dangerous somewhat for inefficacy of water bars and for liquefaction of foundation sand soil.