Dynamic Response Of Soils Around One-hole Double-track Tunnel Based On The Metro Train-meeting

Single-hole double-track shield tunnel with large diameter has been one of the optimized schemes for those subway running tunnels crossing long-water areas.Compared with single-hole single-track tunnels,train-meeting scenarios occur in single-hole double-track tunnels,which results in the larger dynamic loading and longer action time.By far,the thorough understanding of the dynamic response and liquidability of soils around the single-hole double-track tunnels,when crossing liquefiable soil layers,is still lacked.In this paper,a typical profile of the crossing-river section of Nanjing metro line 10 near Jiangxinzhou Station is taken as an example.Based on the multi-body dynamics to establish the train-rail coupling model,and obtain the train dynamic load.Then,in view of the single running scenario and four typical meeting scenarios,the train-tunnel-soil FEM model is developed to analyze the dynamical response of the soils around the single-hole double-track tunnel,and the parameter sensitivity analysis was made by orthogonal test.Conclusions are drawn as follows:(1)In the straight railway section,the horizontal load of the train is only one tenth of the vertical load.During the train passing period,the forces of the wheel on the fixed point of the rail show a periodic change.(2)The vertical acceleration of soil in three parts,the tunnel surfsce,arched waist and substratum,exhibit exponential attenuation trend with the increase of distance,and the horizontal acceleration of the surface has an enlarged area between 10-25m from the tunnel centerline.(3)The maximal displacements of the soil layers beneath the tunnel exhibit linearly decreasing tendency with depth.The maximal vertical displacement of the 8 s meeting scenario exhibit the largest of the 4 scenarios,and that of the 16s,12s meeting and the 8 s single running scenarios exhibit the second largest,the third largest and the least,respectively.The maximal pore water pressures exhibit exponential attenuation trend.(4)The ratio of the maximal pore water pressure to the total stress is less than 1,meaning that liquefaction does not occur in the silty-fine sand layer beneath the numerical example of this paper.(5)The dynamic response of the soil layers beneath the tunnel is closely related to the trainn’s own conditions(speed and capacity),the damping ratio of the soil,the elastic modulus,the density and the tunnel burial depth,the influence of the poisson’s ratio of the soil and the internal friction Angle on the dynamic response can be ignored.