Research On Stability Of Surrounding Rock In Slope Layered Tunnel Based On In-situ Monitoring

Stability analysis of surrounding rock mass layered has become one of the most important subjects in tunnelling engineering research.With the rapidly increasing number of constructing tunnels,it makes the demands of stabilization of surrounding rock mass and optimization design of initial support especially for slope layered surrounding rock more and more seriously.And the key of solving these problems is to make clear of the stability condition of surrounding rock mass under initial support,which will improve the tunnel construction technology and ensure the tunnel's safe employment.So the key needs further study and exploration. From the slope layered tunnelling surrounding rock, practical construction work of Cuntan tunnel in Chongqing,and combined with the site monitoring results of the actual tunnel, the mechanism of slope layered surrounding rock deformation and the stability factors as well as stability are studied systematically in this thesis. The purpose is to establish a theory and technology method for evaluation and judge sability condition of tunnel surrounding rock mass layered in tunnel excavating.Contents and resulting achievement of this paper are as follow:(1) Firstly, the common characteristics of deformation failure and factors affecting the stability of slope layered surrounding rock are analyzed in the paper.Secondly the main failure modes of these were also summarized. According to practical monitoring and measurement work of Cuntan tunnel in Chongqing,which is belongs to typical type of slope layered surrounding rock, stability of surrounding rock can be evaluated and judged.And it has significance in guiding the design and construction of tunnel.(2) Based on careful research that theory of surrounding rock pressure of road tunnel,application of structure mechanics analytical principal,the solution of relationship between the stress at any point within steel arch and the pressure of the surronding rock and distribution range will be solved so that the supporting parameters can be confirmed by the surronding rock and distribution range estimated from the measurement data of tunnel steel arch stress.(3) Accoding to slope layered surrounding rock, based on the measured axial force of fully grouted rock belts in monitoring and measurement of tunnel, and considering theory of elastic-plastic ,the relation between the maximum axial force of rock belts and radius of plastic and loose limits of rock around is deduced.(4)The tunnel excavation and construction process of the slope layered surrounding rock was simulated by using the ANSYS. On the basis of simulation with the plane plastic finite element, by contrast with results under homogeneous surrounding rock,the stress distributed in the construction processwas discussed which provided with reference to initial design and construction and key points of monitoring and measuring.Finally,the results of analysis are used to predict and evaluation rationality and security of initial support.