Numerical Analysis Of The Influence Of Overlapping Tunnel With Shield Method On Underpinning Pile

Since 1990 s, the development of the cities has improved continuously during more than 20 years.There are more and more buildings of public place of entertainment, commerce and residential communities to be built. The bigger cities, the more crowded the urban transportation is. The subway has become one of the main ways of urban transportation in order to release traffic pressure. In particular, the subway is restricted by the crowded environment, and more and more application of all kinds of overlapping tunnel were built. In the process of tunnel excavation,it is underpinning piles that is an effective measure to protect the existing construction. Metro technology in China is still at the growing stage. Damage problems caused by the ground deformation to the buildings still exists, so that it is necessary to strengthen the research in this area.This paper firstly has a brief introduction of some engineering technology such as shield tunnel excavation, underpinning pile, and the application of overlapping tunnel. At the same time,the calculation method and theoretical basis of the finite difference software FLAC3 D are described. The research status of the shield tunnel excavation both at home and abroad is analyzed, and some problems in the current are summarized. Finally the stress and displacement data of underpinning pile foundation after excavating overlapping tunnel at the part of ShenZhen are analyzed by using the finite difference software FLAC3 D.The main research program is as follows:1.The model of redistribution stress and underpinning pile foundation is established, and the process of overlapping tunnel excavation is stimulated.According to the Peck correction formula,the value of surface settlement is numerically calculated by MATLAB software, and the the curve of settlement is obtained. The settlement curve of calculation and the value obtained by the finite difference model are compared. Then the feasibility of the model is verified. The value of pile settlement obtained by the finite difference model and the measured datas are compared to verify the rationality of pile-soil model.2.On the basis of the reasonable model, different finite difference model are established respectively by changing the sequence of overlapping tunnel excavation, the spacing of the overlapped tunnel, length,diameter and space of the pile. Then the datas of the stress andsettlement of the pile foundation are obtained and the results of influences are analyzed.