Analysis On Seismic And Train Vibration Of Shield Tunnel In Peat Soil

With the rapid development of Chinese economy and the acceleration of urbanization,the pressure of urban transport is increasing,the subway has become a major means of relieving urban traffic congestion.Shield construction method has the advantages of safety,high efficiency,low disturbance to the surroundings,which has become the mainstream method of urban subway construction,however,the resulting a series of engineering problems have caused the great attention of experts and scholars at home and abroad,especially for shield tunnel of soft soil area,deformation and stress of shield tunnel during long-term operation have attracted increasingly public attention.Combining with shield tunnel of peaty soil layer in Kunming area,this paper carries out dynamic charateristics research of single-hole shield tunnel under seismic load and train vibration load,which mainly studies the inhomogeneous formation has influence on dynamic response of shield tunnel,this paper main research work is as follows:(1)This paper does a certain amount of dynamic triaxial test on peaty undisturbed soil and improved soil,which determines various dynamic parameters of peat soil under vibration,such as dynamic friction angle,dynamic cohesive force,dynamic modulus,so that provide calculation parameters for research of deformation and stress under dynamic load.(2)This paper studies transverse seismic response characteristics of shield tunnel under different deposit conditions of peat soil,the results show that when surrounding strata is rich in peat soil interlayer,shear force and bending moment of tunnel structure are bigger in the conditions of peat soil on both sides and underlying peat soil;When overlying or underlying peat soil around tunnel,contact point of formation interface and tunnel structure produce abnormal dynamic stress concentration,which is the weak part in terms of seismic design of tunnel structure;Foundation reinforcement can effectively reduce the deformation and internal force of tunnel structure,namely,the higher the foundation strength,the more significant damping effect.(3)Based on longitudinal equivalent stiffness model,this paper studies longitudinal dynamic response of tunnel structure under seismic wave of different incident direction,and calculates the longitudinal rotation angle of ring segment,lining and bolt stress,which finds out contact point of formation interface and tunnel structure is the weak part in terms of longitudinal seismic design of tunnel structure;the longitudinal stress of tunnel structure of the condition of longitudinal incidence is more unfavorable than transverse incidence under equal horizontal seismic load;This paper reveals that basic rule of longitudinal stress of tunnel structure under different angle of formation interface and different buried depth of shield tunnel;Foundation reinforcement can effectively reduce the deformation and internal force of tunnel structure,namely,the higher the foundation strength,the more significant damping effect.(4)This paper studies that the subway train vibration load effects on the settlement of shield tunnel operation under homogeneous stratum and inhomogeneous stratum,which reveals elastic-plastic deformation law of stratum and tunnel structure under the forced vibration;when shield tunnel across inhomogeneous stratum,the subway train vibration load will cause longitudinal differential settlement of tunnel arch bottom,which has a significantly adverse impact on the long-term safety of shield tunnel.Foundation reinforcement can effectively reduce the deformation and internal force of tunnel structure,namely,the higher the foundation strength,the more significant damping effect.