Study On Dynamic Response Law Of Tunnel Lining Structure Considering Spatial Variability Of Surrounding Rock Parameters

Rock and soil are affected by differences in mineral structure,sedimentary conditions and other geological processes,resulting in spatial variability of mechanical properties of rock and soil,which will affect the dynamic response of tunnel under train moving load.at present,the deterministic checking design method based on experience is widely used in tunnels,ignoring the heterogeneous characteristics of soil,and sometimes inaccurate results will be obtained if the spatial variability of rock and soil parameters is ignored.Will reduce the safety reserve.Therefore,based on the spatial variability of geotechnical parameters,this paper takes the lining structure of highspeed railway tunnel as the research object,using the methods of theoretical analysis,numerical simulation and quantitative statistics.The dynamic strain,dynamic stress and acceleration of the tunnel under the spatial variability of surrounding rock parameters are studied.The main research contents and results are as follows:(1)Based on the random theory of spatial variability of geotechnical parameters,the discretization of random field is realized with the help of covariance matrix,and the mapping of random field in FLAC3 D is realized.the train load is directly acted on the rail by artificial vibration,and the time of dynamic calculation is reduced by dynamic multi-steps.according to the engineering parameters of Taihang Mountain Railway,a numerical model is established,and the modeling ideas and methods are verified.(2)Through the simulation and statistical study of 500 times under each working condition,it is found that the dynamic displacement of the tunnel under the spatial variability of the elastic modulus parameters of the surrounding rock is larger than that of the deterministic model,and the increase of the coefficient of variation has no obvious effect on the dynamic stress and the acceleration of the top structure of the tunnel.it has a significant effect on tunnel deformation and bottom structure acceleration.Under the spatial variability of cohesion parameters,the dynamic stress of the tunnel is smaller than that of the deterministic model,and the increase of the coefficient of variation has no obvious effect on the dynamic deformation of the tunnel and the acceleration of the top structure,but has obvious influence on the dynamic stress of the tunnel and the acceleration of the bottom structure.(3)The fluctuation range is within 3 times the diameter of the tunnel,which has an influence on the dynamic response of the tunnel.When the fluctuation range exceeds3 times the diameter of the tunnel,the influence of the increase of the fluctuation range on the dynamic response of the tunnel decreases.When the elastic modulus and cohesion vary at the same time,the dynamic response law of the vertical deformation and acceleration of the tunnel measuring point is the same as that of the spatial variation of elastic modulus,and the dynamic variation law of the maximum principal stress and cohesion parameters is the same.(4)The change of driving speed has almost no effect on the dynamic stress of the tunnel,has little influence on the vertical deformation of the tunnel,and has a great influence on the acceleration of the tunnel.Under different variation conditions,the influence of dynamic deformation and acceleration of tunnel is as follows:deterministic model < cohesion parameter variation < elastic modulus parameter variation and elastic modulus parameter variation at the same time.Train axle load has little effect on tunnel acceleration and maximum principal stress,but has obvious influence on tunnel vertical deformation.When train axle load is 20 t,compared with deterministic model,the vertical deformation of inverted arch increases by 17.6%under the simultaneous variation of the two parameters.