Research On Explosive Effect And Damage Assessment Of Subway Tunnel

Due to large capacity and fast speed of subway,the transportation network in underground space of the city has become a good solution to solve the problem of the traffic congestion.As an important lifeline engineering,the construction and maintenance cost of subway is high,the use period of subway is long.During the operation of subway,the terrorist attack is extremely easy to result in a large number of casualties and economic losses.The explosive effect and damage of the subway tunnel is a complicated problem,involving the explosion and shock dynamics,structural dynamics,damage mechanics,fluid-solid coupled mechanics,the theory of structure and soil interaction.With development of computer technology,numerical calculation,which is less affected by the environment,can change state parameters conveniently,compared and analyzed results,sum up change tendency of important parameter.Subway is a closed urban underground space,and air flow field is extremely complex in the subway tunnel when TNT explodes.The shock wave will reflect,refract and superpose when spread to the lining structure.The peak overpressure in the subway tunnel is obviously different from the peak overpressure in the free air field.The propagation law of the shock wave is studied and researcher put forward a lot of experience formula at home and abroad.The environment of subway is relatively closed and peak overpressure of blast loading empirical or semi-empirical formula is based on experiments in free air field.The peak overpressure is obtained by formula is obviously different from the actual peak overpressure in complex underground environment.The dynamic response and damage of concrete lining is complex under blast loading.This paper using the finite element analysis software to establish the source-air-concrete lining-soil dynamic interaction model of subway tunnel,to study propagation and change law of shock wave in the concrete lining,to discuss dynamic response and damage assessment under blast loading,to provide the design basis to design of concrete lining.The results show that when explosion occurred in the subway tunnel,explosion generates high temperature and high pressure expand gas in a short time.When shock wave spread to concrete lining,it will lead to the nonlinear response and dynamic damage of concrete lining.Velocity and acceleration change of concrete lining is related to the overpressure.The effect of shock wave on concrete lining is larger in the vicinity of explosion.With the distance increase,the influence of shock wave is weakened gradually.The distribution law of the blast loading is related to the explosion,explosive weight and altitude.The foamed aluminum is a good energy absorption materials,which can effectively attenuate the energy of shock wave.The foamed aluminum is the effective measures to improve the explosion protection ability of subway tunnel.