Study On Safety Of Emergency Parking Strip In Shuangbei Tunnel

This paper takes ChongQing ShuangBei tunnel as actual engineering background,according to the practical section size, parameters of surrounding rock and supportmaterial as well as construction methods, using large-scale finite element softwareMidas GTS to simulate the Emergency Parking Strip’s construction process and toanalysis the Emergency Parking Strip only supported by initial liner. Such as thestability and safety factor of rock mass, the displacement and stress of initial liner invariable cross-section, and the justifiability of lining parameters under various operatingconditions.①Using Midas GTS software to build a two-dimensional finite element model inorder to get a plastic numerical simulation analysis on the tunnel only supported byinitial liner under the four actual conditions (depth of100m grade III rock twin-tube,depth100m grade IV rock twin-tube (bench method); depth of100m grade IV rocktwin-tube (Two Side-wall Pilot Tunnel) depth of150m grade IV rock single tunnel).Focuses are on the displacement of the tunnel widened segment with strength reductionfactor the curve, the safety factor of each condition calculated from the criterion ofinstability of the tunnel. The surrounding rock displacement, distribution of stress andplastic zone under the parameters of practical support are also analyzed. Characteristicvalues combination obtained were compared for selected construction program②By the beginning of the transition section in the actual establishment ofthree-dimensional finite element model of the rock, in the depth of100m III-class rockconditions, the analysis of the overall stability of the Canadian broadband Shuangbeitunnel junction with ordinary paragraph (tapered) transition section, the analysisdisplacement, stress and plastic zone features support parameters, while analyzing theforces sprayed mixed layer, draw the most unfavorable position by the force of variablecross-section of the transition section and reinforcement measures need to be taken inthe case.Obtained by the above methods the following conclusions:①The results of numerical simulation and on-site monitoring and measuringcontrast to the measured data to determine the correct numerical results rationality, bothcomprehensive analysis of the deformation of large-span tunnel section and specificity,and ultimately determine the tunnel plus broadband Shuangbei safety factor.②Whether from the surrounding rock displacement or from stress of the supporting structure, the widened section of the junction with the common segment(tapered) end bearing most unfavorable position at the right side of the arch are waistlevel convergence value reaches11.51mm, while spraying mixed layer the emergenceof tensile stress, and the value reached0.323Mpa, therefore construction should payattention to the order of the tapered end of the reinforcement, shotcrete thickness can beincreased if necessary at the end bearing, or at the end of the Order of the implantedanchor also ensure variable security section.