Study On Bearing Capacity Of Subway Tunnel In Soft Soil Under Shock Wave

Many metropolitans in China, such as Beijing, Tianjin, Shanghai, Guangzhou and Chongqing, have been busy with the construction of railway transit system in the past few years, and nearly formed a convenient network. Moreover, in Tianjin, Shanghai and Guangzhou, most part of the railway transit system in the downtown area is subway built in the tunnels in soft soil.Most existing civil air defence works in China were built mainly to defend against the attack of nuclear weapons, and since the metro tunnels are considerably strong enough to resist the shock wave generated by nuclear explosion, they are often the evacuation passages in the network of civil air defence works. In modern wars, however, hi-tech conventional weapons with surprising accuracy and astonishing destructive effect have been widely used, and they are mainly used to attack military projects and city life-keeping facilities which are of strategic importance. Though it is little possible that urban metro tunnels are attacked directly, once the important buildings neighboring them are under attack, they are probably damaged. So it is necessary to evaluate their bearing capacities in this situation. Because the resistance ability of soft soil against blast wave is weaker than that of rock, the typical case in the situation mentioned above is to estimate the bearing capacities of urban subway tunnels in soft clay, which could help to present valuable advice to the construction of downtown subway tunnels.Researches in this dissertation cover the followings five aspects:(1) Dynamic triaxial test to establish the constitutive model of typical soft clay where urban subway tunnels in Shanghai mainly lie, and to get their relating parameters.(2) The propagation rule of shock wave induced by explosion of conventional weapon in soft soil, and analysis theory, calculation method to evaluate the response of subway tunnel in soft clay under blast wave.(3) Dynamic behavior simulation of tunnel segment joints under blast wave in soft soil.(4) Bearing capacities evaluation of typical subway tunnel in soft soil under blast wave.(5) Safety distance between the subway tunnel and charge in fulfillment of tactical and technical requirement.Finally, conclusions are presented, as well as further research aspects are suggested at the end of the dissertation.