Multi-span Shallow Tunnel In Land Subsidence Control Technology

Shallow-buried excavation law obtains widespread application because of its simple job practice and strong compatible. And construction tunnel at shallow depth damages stratum, stratum stress is freed and corresponding deformation is generated. For deformation there is biggish difference due to difference of stratum conditions. Therefore studies of the reasonable prereinforcement measure and the construction labor law controls the surface subsidence isextremely essential. For the typical multispan shallow buried tunnel, the mechanism of the the pre-reinforced measure to controle the ground settlement was studied and the reasonable working operation was developed by the relation derivation and the numericalanalysis in this paper. The main research work is as follows:1,The surface subsidence mechanism caused by excavating and draining was summaried and analysised based on Biot consolidation theory.2,The function mechanism of pipe roof was analyzed and the requirements for "shed" and "frame" to developed on the tunnel arch was put forward, According to the theory of shed and frame, it is pointed out that roof can consolidate the ground and disperse the ground stress and reduce the excavation stress.3,The yield functions were deduced under the passive earth pressure conditions based on Mohr-Coulomb failure criteria.4,The reasonably width of tunnel excavating step by step is determined by the soil arch effect.5,According to the characters of the tunnel excavation, This article simulates influence caused by tunnel excavation on ground surface deformation through "Birth"and "Death" method of finite element. Meanwhile the study provides gist for construction procedure and grouting bound of similar project.