Fatigue Life Evaluation Of Shield Tunnel Segment In Karst Geological Condition Under The Dynamic Load Of High-speed Rail Trains

The current urban subway construction in full swing,in the tunnel construction the probability of meeting karst geological increase greatly,What effect does the existence of the karst cave have on the stress and fatigue life of the tunnel segment?The distance between the location of the hole,the geometry size,the distance between the cave and the tunnel,and the physical mechanical properties of the rock layer are affected by the fatigue life of the pipe.In this article,the fatigue life of tunnel tube is studied by using abaqus for dynamic numerical simulation.The main research is:1)Refer to the result of the empirical formula and power calculation of scholars both at home and abroad,found at the bottom of the shield tunnel medial segment of the tensile fatigue life N is minimum,so take the bottom of the medial segment of the tensile fatigue life as the fatigue life of tunnel lining segments.2)the fatigue life of shield tunnel segments is found by comparing the fatigue life of the shield tunnel tube in different dynamic combination mode,and the most unfavourable dynamic combination method is found,namely,the dynamic load combination mode 3.3)the calculated comparison shows thatthe fatigue life of the shield tunnel is associated with the size of the hole in a certain depth Within a certain range,the size of the cave has an impact on the fatigue life of the tube.the fatigue life of the tube is increased by the distance between the hole and the tunnel.When the distance is too small,the existence of the karst cave can cause great influence to the segment of the fatigue life lead to do not conform to the requirements of the design,so in the design and construction need to detect karst caves and the distance between the tunnel is determined.take measures to deal with it4)The fatigue life of the tube is related to the location of the cave,below the karst cave in tunnel,The fatigue life of the pipe increases with the distance between the tunnel and the tube.And the hole in the tunnel underneath the tunnel is a lot worse than the bottom of the tunnel.Therefore,it is important to detect the hole at the bottom of the tunnel while working in the tunnel,and judge whether it is necessary to deal with it according to the distance of the tunnel.