The Research On Mechanical Behavior Of Support Structure And Construction Sequence Of Multi-arch Tunnel With Shllow-depth And Unsymmetrical Pressure

The phenomenon of unsymmetrical pressure in Multi-arch tunnel caused by the complex terrain conditions and construction sequence is widespread in the actual construction process. In the condition of tunnel terrain bias have been identified, how to adopt reasonable construction methods and construction sequence to reduce the impact on support structure by construction bias is caused more people’s attention.Regarding Xiong Mao dong tunnel project in hunan province as background, establishing the overall model of Multi-arch tunnel with shllow-depth and unsymmetrical pressure by numerical analysis method, making use of the measurement data by contrast analysis method, the research which is about mechanical behavior of support structure in the construction process was deeply done in this paper. The research topics include the following aspects.(1)According to the Multi-arch tunnel practical construction method, considering different bias angle and depth conditions, aiming at first excavation of the buried side and the first excavation of the shallow side of the two construction program for the bias arch tunnel, finite element program was used for research which was about different lateral excavation order have influence on stress and displacement impact of the middle wall, ining, initial support and surrounding rock. Eventually, the research get the reasonable conclusion of horizontal construction sequence.(2)Combined with numerical simulation basic theory of tunnel dynamic construction, reasonable to select the mechanical parameters of rock and supporting structure, considering the two conditions of frist appling for the lining and the first excavation of the right hole after left cave excavation was complete, respectively, to establish the three dimensional model of the two conditions and to analyse its construction process of the numerical simulation, focusing on the mechanical behavior of the supporting structure in the bias effect.Ultimately,Stress distribution of the middle wall and initial support and reasonable construction consequence of lining were obtained. It also could provide theoretical guidance for the dynamic tunnel construction.(3) Combined with field monitoring data, to grasp the surrounding rock dynamic, to understand the status of the supporting structure, combination of numerical simulation results by contrast analysis method, the conclusion that numerical results have a certain credibility was obtained, at the same time to evaluate the safety of the component, and the conclusion of the middle wall the lining and steel arch were safe in the construction process was reached.The conclusion could also provide security information for the tunnel construction and long-term use.