Research On The Damage Mechanical Characteristics Of Shield Tunnel Under Derailment Train Impact

Train derailment accident will not only cause significant casualties and property losses,but also pose a huge threat to the safety of rail infrastructure.When the derailment accident occurs in shield tunnels,the violent impact between the train and segmental lining will lead to many significant safety accidents,such as bolt failure,segment damage and deformations,concrete breaking and spalling,which may eventually destroy the structural stability of tunnel lining,and even lead to the local collapse or overall scrap of shield tunnel.Therefore,in order to reveal the structural failure characteristics of the shield tunnel resulting from train derailments,and provide guidance for the targeted design of the shield tunnel,based on the impact dynamics and the concrete damage-fracture theory,a finite element model considering the joint effect and nonlinear dynamic contact coupling between train-tunnel-stratum is established.As a result,a series of dynamic failure mechanism of shield tunnel under the train impact,include the failure of segmental joint bolt,the plastic damage and the brittle fracture of the segment lining,are studied.The main research results are as follows:(1)Based on the principle of virtual work and the continuum theory,the theory of impact dynamics is expounded and the dynamic control equation of impact is presented.Meanwhile,the characteristics and applicable scopes of two different dynamic time integral methods are compared,and the dynamic contact theories of impact,including contact constraint conditions and contact interface algorithm,are systematically summarized.(2)A method for simulating the mechanical effect of segmental joint is presented in this paper.Based on the failure criterion of the connector elements,the failure range,failure mode and failure order of joint bolt are compared and analyzed in two cases.After that,the sensitivity analysis of the bolt parameters and the impact velocity on the failure characteristics of the joint bolt is carried out,and the influence of bolt failure on the damage and and deformation of segment lining is proved up.(3)Based on the kinematic contact algorithm,a nonlinear dynamic contact coupling model of train-tunnel-stratum is conducted for the analysis on the deformation and energy conversion characteristics of the train and the characteristics of impact load.The dynamic response characteristics and anti-collision capability characteristics of the train during the impact process are revealed.Meanwhile,the displacements,deformations and damage characteristics of tunnel lining are proved up.(4)Based on the plastic damage and brittle fracture theory of concrete,the influence of the impact velocity on the dynamic response of shield tunnel is explored,and the local crushing range,the crushing process and the crushing evolution law of the concrete lining under the train impact are analyzed.In addition,on the basis of summarizing the interface connection type and principle of the multi-scale structure,a multi-scale model of the segment structure considering the joint effects is proposed,and the multi-scale simulation technology of shield tunnel for the train impact is developed.At the same time,the feasibility and practicability of multi-scale model in static calculation of segment structure and solving complex dynamic problems are verified.