Finite element analysis of effects of shield driven tunneling on pile foundation

Process of shield driven in Tianjin Metro Line No.1 project is simulated by means of finite element method.Pressures and shearing forces are enforced on the soils to simulate the real reactions between shield driven machine and the surrounding soil during tunneling.Results from the model adopted here by the finite element method are fine agreement with those acquired in the Tianjin Metro Line No.1 project.Researches on the effects of shield driven tunneling on the pile foundation nearby are carried out with this model.The settlement at pile top and displacement along pile caused by shield driven tunneling nearly reach their maximum values during the process when the shield driven machine is approaching the pile;when it is leaving away from the pile,the increments of settlement and displacement are small.Under the same conditions,settlement at the top of long pile is small because the side resistances at the lower part of long pile can be exploited to a great extend.During the process of tunneling,pile with the length of 12 m inclines while piles with the length of 16m and 19 m bend and the maximum moments are at the position 12-13 m below the ground.During tunneling,there are back and forth displacements at pile top along the direction in which the tunnel is pushed forward.The greater the load applied at pile top,the larger the settlement caused by tunneling at pile top.