STUDY ON LONGITUDINAL DEFORMATION MECHANISM OF CUT AND COVER SUBWAY TUNNEL DUE TO GROUND SETTLEMENT

Abstract

 Large magnitude of settlement and many cracks were observed in a part of the longitudinal direction of the existing cut and cover subway tunnel in soft ground. It is important to evaluate accurately the load bearing performance of the subway tunnel for the long term safe service. It was found from the in-situ measurement results of the reinforcing bar strain values that the position of neutral axis on the tunnel cross-section is different from the position obtained from a conventional calculation. An apparent axial force acting along the tunnel longitudinal direction is assumed to be generated due to the effect that the tunnel extension movement with the cracks induced in the tunnel lining is constrained by both end parts of the tunnel without the deformation and is approximately estimated. It was found from the numerical calculation results that the tunnel damages such as a distribution of cracks in the tunnel lining can be reproduced accurately by using the apparent axial force and a quasi-three-dimensional model.