Analysis And Monitoring For Structural Behavior Of Initial Supports Of A Highway Tunnel Under Construction

To keep safety and quality of the tunnel construction, the Highway Tunnel informatior construction should adjust support parameter dynamically with the geological conditions of the tunnel face and the result which the Tunnel Seismic Predication display.In weak surrounding rock section, the tunnel initial support has a direct impact on surrounding rock stability which consist of the steel arch and anchor sprayed concrete.In the common condition of surrounding rock properties, support material and invariant parameter, the distance of initial support become a important parameter in thetunnel construction.However, in the actually project, the parameters values mostly judged by personal experience, how to thorough scientific and rational way to quantitative analyze this parameter, it is worthy to be studied and discussed in-depth.The article is manly based on the background ofa highway tunnel, according to the geological condition of construction tunnel face, in tunnel construction, by geology radar advanced geological prediction, the result indicated that the classification of tunnel surrounding rock of 30m in front of the tunnel face on construction are in range of V. Viewed from the tunnel face, the steady ability of surrounding rock is low,so it’s necessary to optimize and adapt the steel arc design support parameter, that’s to say, choosing a optimum value between 0.5 to 1.2 meter. Aim at the problem of initial support optimized parameter about weak surrounding rock, the main contents are as follows.(1)According to the method of the tunnelfinite element analysis of load -stratum model, established a simplify 3-D finite element model and a plane strain model with different distance of arch steel in initial support system,for considering the various of plastic zone,the surrounding rock adopted elastic-plastic constitutive relation and the anchor, steel, sprayed concrete analysis as elastic material. Obtaining the calculated result of deformation and stress of the initial support system by the large-scale finite element analysis software ANSYS and MIDAS/GTS’calculated result.(2)According to the mechanical characteristics of the initial supporting structure system, simplified the steel-sprayed concrete as steel-concrete compression-flexure member, checking the bearing capacity, checking tensile strength of the anchor svstem, and then analyze and demonstrate the initial support parameter, that is, space setting on steel arch about reasonability and safety. And on that basis, putting forward a safety and reliability space on steel bracing, which could be used as the basis of supporting parameter’s alteration and applied to construction site.(3).Then carried out the monitoring in the corresponding sectionsusing relevant monitoring results to compared with calculationresults.The related engineering practice proved the rationality of calculations results.