Analysis Of Shield Tunneling Factors And Research On Stability Of Adjacent Pile

With the expanding size of the city and sharply increasing population, underground space is continuously developing and the number of urban subway construction is growing. The increasing subway lines cause that the shield construction will inevitably go through complex underground structures, affecting on the existing buildings and infrastructure. It is an important issue to control the ground settlement and the effect on adjacent pile in the construction. Therefore, analysis of shield tunneling factors and research on stability of adjacent pile have very important practical significance.Based on the intervals crossing Yuhu railway, theoretical calculations and numerical simulation are combined in this paper. According to Mindlin solution, ground horizontal and vertical settlement formulas during the excavation are summed up which assume that soil displacement caused by the soil volume loss, positive additional thrust and friction are independent. Meanwhile a new method to calculate adjacent pile settlement is carried out considering different soil conditions based on two-stage analysis and Winkler foundation model. In addition numerical simulation has been done to verity and supplement the theoretical calculation which analyzes the iMPact on ground subsidence caused by different depth of tunnel, supporting positive pressure and friction as well as the iMPact on adjacent pile during tunnel excavation caused by different pile conditions. The trend of numerical simulation and theoretical calculation results are the same.Research shows that the greatest iMPact on surface subsidence is tunnel depth, followed by the friction between the shield machine and soil, and the iMPact of the additional thrust is the last one. When the tunnel depth is relatively deep or the friction coefficient is relatively large, a certain uplift will occur on the ground in front of the excavation surface. The iMPact on adjacent pile caused by excavation decreases with the increasing pile length and horizontal distance between the pile and tunnel. When the distance is greater than 4 times of tunnel radius, theoretical calculations and numerical simulation prove that the iMPact on pile is too small to take into consideration with the result of the pile settlement less than 3mm o In this paper, numerical simulation has been done to analyze the two-lane tunnel project based on the concent above. The simulation results show that the ground settlement above the right line which has been excavated first is slightly larger than the left one. When the two-lane tunnel excavation is complete, the piles biased to the right sink more than the other side. In the same side, the settlement of the middle pile is the smallest one and the top one is the biggest. The largest settlement is 9.8mm, which meets the regulatory requirements.