Optimum Design Of Initial Support Of Uunsymmetrical Loading Tunnel Underdifferent Surrounding Rock Level Conditions

Bias of the complexity of the tunnel,through the engineering analogy method in practical engineering design of the initial supporting the construction and operation period appeared many problems,so for terrain bias tunnel primary support structure is necessary to in-depth study,analysis and optimization design.Based on the existing tunnel of shallow bias,through information research,theory analysis and numerical simulation of bias tunnel primary support system of anchor length,anchor spacing and thickNess of sprayed concrete optimization design.This article USES the finite element numerical simulation software MIDAS/GTS/NX 2-d numerical model is set up,according to the original design and specification for design of highway tunnel(JTG D70-2004)design the bolt length,spacing,and the various working condition of the shotcrete layer thickNess,simulation analysis,finally combining with engineering economy to make optimization design.Through study the following results:1.According to the back channel tunnel engineering geological conditions,geometric parameters and surrounding rock physical and mechanical properties of the corresponding numerical simulation model is established,using the method of numerical simulation analysis was carried out on the bias tunnel primary support.Of each design conditions given tunnel characteristics of displacement,stress and bending moment,the plastic zone of surrounding rock,lining of shaft bolt axial force and so on,and carries on the research and analysis.Eventually give back tunnel primary support level IV and V level of surrounding rock under the condition of optimized design scheme.2.Due to the shallow bias tunnel surrounding rock is often broken,V level of surrounding rock,set up the initial supporting parameters,and comparative analysis of the buried deeply 5 m,10 m,15 m,the surface of the dip Angle is 15 °,30 °,45 ° the bias condition of tunnel primary support under the condition of combination,through comparing the distribution of plastic zone and the surrounding rock stress,displacement of surrounding lining stress,kNown:(1)for the bias tunnel,buried depth and surface inclination Angle will affect the stress of the tunnel primary support,so to comprehensively consider the buried depth of tunnel and surface inclination.(2)For bias tunnel,the use of asymmetric supporting structure design more symmetric design is more reasonable.3.On the basis of optimized scheme,to guide the tunnel construction,guarantee the security andstability.