A Study On Construction Technology In Undercrossing Ultra-shallow Buried Tunnel Under Complex Conditions

Taking Xiamaixi Tunnel in the rail transit Line 1 in Guiyang as background and integrating the methods of theory analysis, numerical simulation and live monitoring,this paper analyzed and studied the construction stability of ultra-shallow buried tunnel undercrossing existing architectures in southwest China and its influence on environment. The following are the major work progressed and the conclusions:(1)Targeting at the construction stability of undercrossing existing highway and its influence on the operating highway, we systematically analyzed and studied the deformation of wall rock and the development of the plastic zone during construction when employing different construction plans such as the twin side heading method,CRD method, CD method and the benching tunneling method etc. to the shallow buried tunnel and the specific influence of press and deformation of the tunnel’s supporting structure under different construction schemes. We determined the construction scheme of undercrossing the highway, proposed advices for construction technology, and directed the tunnel’s construction. In tracking the live construction, it indicates that the recommended construction scheme is safe, feasible and controllable in ground subsidence of the highway coursed by the construction.(2)For the vibration effect aroused by short distance blasting work in crossing the existing transit culvert in Xiamaixi Tunnel, we adopted numerical simulation to analyze the blasting vibration response of the existing transit culvert structure caused by blasting and excavation; determined the blasting scheme of ultra-shallow buried tunnel undercrossing the existing large transit culver’s large-section; optimized the method of blasting construction and yielded the mathematic relationship of the maximum vibration rate of blasting and the distance to ensure safety of the construction.(3)For the instability issue of Xiamaixi Tunnel caused by rainfall infiltration of the subgrade slope in crossing the highway, with numerical analysis we studied the side slope’s damage process under the effect of rainfall infiltration in the process of the shallow buried tunnel crossing the side slope in southwest mountainous towns. We came up with appropriate supporting schemes to provide technology support for optimizing the construction and guided the construction work of the project with great results achieved.