RESEARCH ON SOIL DEFORMATION INDUCED BY OVERLAPPED TUNNELING IN STRATUM SOIL

Soil deformation and construction stability encountered in overlapped tunneling should be well controlled, especially in stratum soil, so pre-reinforcement with pipe grouting and waterproof grouting always are applied for those targets. The pre-reinforcement retains the tunnel face stability which is dominated by stress relaxation of excavation. The waterproof grouting is aimed to alleviate the seepage that would cause soil settlement after construction. Based on Sheirzhen Metro Line 5 overlapped tunneling section, numerical analysis is utilized to survey the stress relaxation and seepage application on the lining and soil deformation during the difference tunneling stage. When the down tunneling is processed, the soil immediate settlement induced by excavation is less than the post-construction settlement caused by seepage. In spite of soil consolidation, the stability of lining is discovered. Only the post-construction settlement becoming stable gradually could the up tunneling be conducted. However in the up tunneling, stress relaxation of excavation causes the larger soil settlement than seepage, and the settlement increases rapidly as the stress relaxation rise.