Study On The Stability Of Undercrossed Shied Tunnel On Tunnel Nodes

In the current construction method of the tunnel, shield is a modern construction method with high efficiency, which is widely used at home and abroad. Then, the shield method, the Body and the soil contacts directly and makes the corresponding cutting and rotation in the construction process. Therefore, it is an important measure to ensure the safety of the shield tunnel construction. In this paper, the method is based on the actual case of Nanjing metro shield tunnel construction, combined with the specific geological conditions of Nanjing area. The aim is to study the influence of shield tunnel construction. The main work of this paper is as following:1, Combined with the domestic and foreign literature, the impact of the shield method construction on the existing tunnel stability has been studied. The main subsidence theory and the time and space characteristics of the settlement are analyzed. The factors affecting the construction are analyzed in view of the mechanical behavior.2, According to the actual engineering situation of Nanjing Metro North South line project, three-dimensional simulation of the whole construction process is carried out. And the two kinds of different strengthening modes are considered, which are making uplift pile and soil improvement. The ANSYS (5.6 Edition) is used to analyze and get useful database of the deformation of shield tunnel and the floor of Xuanwu Lake tunnel.3, Based on settlement database, the settlement prediction model of support vector machine, neural network and gray model are established. By the simulation of MATLAB, the differences of model of the first section and the second section of shield machine construction are 0.22 and 0.43 respectively. The relative error rate is 5.91%. The settlement prediction model can predict the settlement of tunnel and provide early warning for the construction process.