Study On Dynamic Response Of Tunnel Structure In Early Age Stage Under Dynamic Load Of Upper Railway

Major cities in China are building large-scale urban rail transit facilities and vigorously promoting the construction of utility tunnel and sponge cities.Because of the irregularity of railway track and uneven wear and tear of train wheels,the train vibrates under the action of wheel-rail excitation,which will also cause the vibration of surrounding soil layer.The construction environment of tunnel engineering is in the interior of rock and soil,so the disturbance of rock and soil around the tunnel will inevitably affect the construction process.Vibration of surrounding soil may cause resonance of tunnel structure,which may affect the quality of early lining structure of tunnel.Therefore,it is necessary to study the influence of train vibration on early lining structure of tunnels.This thesis relies on the tunnel of the entrance and exit line between Guangzhou Road Station and Xinglonghu Station of Chengdu Metro Line 1,which cross over the existing Chengdu-Kunming cargo outer winding project through.By means of theoretical analysis,field measurement and numerical analysis,the dynamic response regulation of tunnel lining structure in early age is studied thoroughly and systematically.The main research results and conclusions are as follows:(1)The coupling dynamic model of vehicle and track is established to simulate the reaction of fasteners produced by train running at different speeds,and the finite difference three-dimensional dynamic calculation model of tunnel-stratum-track is established.The acceleration response of tunnel lining structure under train vibration is calculated and checked with the field measurement results,which proves that the numerical model and train load have good similarity and reliability.(2)Based on the validated numerical simulation method,the acceleration,displacement,dynamic tension stress and dynamic compression stress response of lining are selected as the dynamic response analysis indexes.Sevearal conclusions of the influence of train vibration on early lining structure are as follows:1)The deeper the tunnel is,and the faster the train speed is,the stronger the dynamic response of the lining structure in early age is.The tunnel structure is significantly affected by train vibration within 10 m depth,while the train speed has little influence on the vertical displacement and dynamic stress response of that.2)The larger the crossing angle is,the weaker the vertical displacement and dynamic stress responses are,while the variation of peak acceleration has no general rule to follow.When the vibration propagates along the tunnel longitudinally,the phenomenon of local amplification appears.When the cross angle increases to 67.5 degrees,the phenomenon of longitudinal vibration amplification along the tunnel will be alleviated.3)The lower the level of surrounding rock is,the weaker the response of acceleration of lining structure in early age is,while the vertical displacement and dynamic stress response increase exponentially,which indicates that the grade of surrounding rock has a great influence on the dynamic response of tunnel structure.4)By means of non-linear fitting method,the single-factor function relationship between the maximum dynamic tension stress of early-age lining structure and tunnel buried depth h,train speed v,intersection angle ? and surrounding rock grade? is obtained.(3)Aiming at the dynamic tension stress response of tunnel lining structure in early age under the cross influence of multiple factors,the PSO-BP neural network model is used to realize the multi-factor non-linear regression.The error analysis results show that the regression accuracy is very high,and it can be applied to the study of the general law of calculation simulation reflecting the change of parameters.