Dynamic Response And Damage Of Lining Structure Of Metro Tunnel Under Multi-point Explosion

With the rapid development of rail transit systems,due to its convenience,low disturbance and high efficiency,the subway has become the"lifeline"of urban transportation.As an important underground passage,once an explosion accident is encountered,it will bring huge casualties and property losses,so the research on the explosion resistance of subway tunnels is of great significance.This paper based on the nonlinear finite element technology,to study the propagation and attenuation law of multi-point explosion shock waves in the formation,the dynamic response law and damage characteristics of lining structures under multi-point explosion loads,The main research contents include:（1）Establish a multi-point simultaneous closed explosion numerical model,analyzing the relationship between the peak pressure of the shock wave and the number of initiation points.When the ratio of the vertical propagation distance of the shock wave to the cubic root of the total charge is more than 1.391m/kg^1/3,the shock wave intensity at a certain position is inversely related to the number of initiation points.（2）Establish two-point and three-point synchronous closed explosion models outside the subway tunnel to simulate the dynamic response of the subway tunnel lining structure,the explosives are arranged symmetrically in the direction of the subway tunnel.The results show that the cross section of the explosion center is the most unfavorable section of the lining structure under multi-point explosion load;the displacement,velocity,and stress of the most unfavorable section of the lining at two-point initiation are 1.0%,7.8%,and 10.2%higher than those at three-point blast.The displacement maximum and velocity maximum appear at the arch top,the stress maximum appear at the arch bottom,and the tunnel displacement is mainly vertical displacement.（3）In order to analyze the dynamic response differences of the most unfavorable sections of the lining under the effects of multiple-point simultaneous closed explosion loads,the subway tunnel models with different explosive point spacing,explosive charge,tunnel burial depth,and cross-sectional shape were selected as research objects.When the distance between the explosive points increases,the peak stress increase of arch bottom is about 8.9%;When the amount of explosives increases,the peak increase of arch bottom stress is around 25.9%;When the buried depth of the tunnel increases,the peak increase of arch bottom stress is around 11.5%;When the shape of the lining section changes from circular to rectangular,the peak stress increases of the lining floor is around 41.6%.When the rectangular section lining is more susceptible to explosion impact damage than the circular section lining.Compared with the distance between the explosion points,the charge and the tunnel burial depth,the explosive equivalent is the most sensitive variable for lining arch bottom stress.（4）The damage characteristics of the lining structure under two-point and three-point explosion loads were studied.By analyzing the stress cloud diagram of the lining structure’s failure process,it was found that the lining damage showed a pattern of minor cracks,local cracks,and through cracks in order;increasing the thickness of the lining structure and properly selecting the strength of the lining concrete can achieve a good anti-blast effect.