Study On The Critical State Of Railway Tunnel Under Usymmertrucal Pressure

With the rapid development of economy and technology,China has gradually entered the high-speed rail era,and high-speed railway tunnels emerge as the times and conditions require.Since trains run much faster in the high-speed railway tunnels than the ordinary trains,it determines that its design of section is correspondingly larger.However,the regulations on bias railway tunnels in the current "Railway Tunnel Design Code"(TB10003-2005)are all based on the low-speed railway standards.If the design calculation and checking of high-speed railway unsymmetrical loading tunnel is conducted in accordance with the existing norms,it is bound to result in calculation results not corresponding to reality and other problems.This article mainly studies the determination on the critical state of high-speed railway unsymmetrical loading tunnel in terms of theoretical calculation,numerical simulation and model test.The study involves the following aspects:(1)Applying the Protodyakonov's theory,on the basis of solving the theoretical critical value of the unsymmetrical loading tunnel with graphing method,we can conclude the formula of calculating the theoretical critical value of the unsymmetrical loading tunnels with different spans can by changing parameters.By formula method,we can solve the critical value of the unsymmetrical loading tunnel with eight different sections considering the thickness of side covering soil,the cross slope,the surrounding rock level and other factors,and thus according to the calculation,analyze the association between unsymmetrical pressure and tunnel span.(2)Applying the finite element software,to conduct numerical simulation to the high-speed railway tunnel with eight different sections considering the thickness of side covering soil,the cross slope,the surrounding rock level and other factors,and solve the unsymmetrical pressure critical state of high-speed railway tunnel,explore the relationship of the unsymmetrical pressure critical value and the tunnel span under the same condition of symmetrical pressure.(3)Through a large number of orthogonal tests,to determine the mix proportionof similar material when the III,IV and V levels of surrounding rock at the similitude ratio of 1:40.(4)Through model test,to verify the unsymmetrical pressure critical value calculated from the passenger railway double track tunnel at 250 km per hour,with the test data to analyze the reliability of the conclusion obtained by theoretical calculation and numerical simulation.