Highway Tunnel Surrounding Rock Primary Support And The Shotcrete Composite Stiffness

In this paper, on the basis of existing research，combined with structural mechanics,rock mechanics, elastic-plastic theory and Large3D geotechnical numerical softwareMIDAS/GTS, of circular tunnel excavation from former until at various stages of thedisplacement and stress of surrounding rock after excavation support, such as asystematic summary and analysis. Put forward the primary support the concept ofcomposite stiffness, use of MIDAS/GTS, primary support for the rationality andapplicability of the composite stiffness were discussed. From the angle of thedisplacement of tunnel surrounding pay close attention to the stability and safety of thetunnel. The main work includes:①To the assumption that the initial stress, etc（the lateral pressure coefficient).Under the condition of induction, summary and secondary elastic-plastic displacementof surrounding rock stress state is deduced and surrounding rock and supportingstructure of the displacement and stress under the action of theory.②Of circular tunnel surrounding rock stress and state of displacement distributioncharacteristics and influencing factors and Supporting structure’s impact on the stabilityof surrounding rock. Clarified the radial normal stress and tangential normal stress ofsurrounding rock, the radial displacement under different conditions of distribution andchange rule.③Using Midas GTS simulation analysis of the circular tunnel elastic-plasticsecondary stress and displacement state. Numerical solution of surrounding rockconditions get Ⅲ level and Ⅴ level of surrounding rock. Compared with theanalytical solution.④From the initial supporting structure system of the mechanical characteristicsand construction features of the shotcrete support, combining with the concept ofstiffness,model based on rock mass mechanics characteristic curve method, andconsider the tunnel structure design method of the advantages and disadvantages ofstructural mechanics and rock mass mechanics, build force model，The study ofcomposite stiffness of highway tunnel surrounding rock and support in the early yearsof the sprayed concrete. Analyzed the influence of the typical parameters of compositestiffness of the tunnel, discuss its rationality, applicability and feasibility.⑤Based on Midas GTS modeling technology, Through the physical and mechanical parameters, starting conditions, boundary conditions,the materialconstitutive relation, unit grid type, etc, to establish the three-dimensional geometricmodel of the tunnel. Using Midas GTS of shallow and deep buried tunnelunder thecondition of surrounding rock conditions goodⅢlevel and Ⅴ level of surrounding rockis analyzed. With numerical solution and early based on highway tunnel surroundingrock and shotcrete support composite stiffness of the tunnel surrounding rockdisplacement of the analytical solution were analyzed. Study the application conditionand its characteristics of composite stiffness.