Study On Long-term Stability Of Surrounding Rock And Supporting Structure Of Tunnel

At present, China has become one of countries in the world that has the largest, the most complicated and the fastest-growing tunnels. Long-term stability and safety of tunnel engineering are closely related to creep of support structure. In this paper, combing with the Chongqing City Natural Sciences Foundation which is the study on the long-term stability of tunnel and its support structure, a triaxial rheological test is performed. And it studies the rheological property of concrete support structure. Considering the rheological property of concrete support structure, the nonlinear finite method is used to analysis the long-term stability of tunnel and its structure and the sensitivity of the rheological parameters.The main work and results are as follows:â‘ The main rheological theories of material are introduced overall, and the characteristics of model theory are emphasized.â‘¡Using MTS815 Hydraulic Servo System, the triaxial compression deformation and rheology experiment of the concrete specimens of secondary lining is performed. It studies the law of concrete axial strain changed with time in different stress level. Rheological parameters of Kelvin-voigt rheological model and constitutive model of LUBBY2 in the finite element method software ADINA are calculated by the analyzing of test data.â‘¢Basic principle and process of finite element method which is used to simulate underground structure engineering are described. Considering the creep property of concrete support structure, finite element analysis program named ADINA and constitutive model of LUBBY2 are used to simulation and analysis of excavation and support of standard section tunnel with two lanes. The results show that the extreme value of the maximum principal stress and the maximum shear stress of surrounding rock, initial support and secondary lining all decrease, but the bolt's axial force increase considering the creep of concrete support structure. The maximum value of horizontal displacement and vertical displacement of surrounding rock, initial support and secondary lining also decreases. Plastic region of surrounding rock is distributed mostly in small part close to both sides of tunnel haunch just at the end of excavation and support, and the range of plastic region of surrounding rock increase with the creep of concrete support structure.â‘£Sensitivity analysis method of system analysis is used to analysis the sensitivity of the rheological parameters of concrete support structure. By comparing different rheological parameters'sensitivity factor, the paper distinguishes the main sensitivity parameters and secondary sensitivity parameters. The results show that sensitivities of rheological parameters according to the maximum principal stress and vertical displacement of crown of surrounding rock are arranged in the following order: a3>a0>a4>a1>a5=a2. And the sensitivities of rheological parameters according to the maximum shear stress of right hance of surrounding rock are arranged in the following order: a3>a4>a0>a1>a5=a2. Namely a3 is sensitive parameter. Parameters a5 and a2 are insensitive.