Effects Of Ground Movements During Shield Tunneling On Adjacent Pile Foundations

With the rapid development of the national economy and the acceleration of urbanization process, a large number of subways are started to construct to ease the traffic pressure. In the modern subway construction, the shield method is increasingly being applied to the construction of the subway tunnel because of its unique advantages. However, the extensive construction of city subway under shield method will be subject to the constraints of environmental conditions. Therefore, many new subway lines have to extend along the overpass, and interwoven through the foundation pile or pile group of the overpass. Such engineering tunneling will disturb the surrounding strata, and cause the soil deformation. Besides, it will cause damage to both the nearby bridge pile foundation and superstructure. Thus, the research of ground movement caused by shield tunneling and its impact on bridge pile foundation is of great engineering significance and academic significance.On the basis of theoretical analysis, and combined with the actual condition of the soil in Beijing, we can use the finite element software MIDAS/GTS to simulate the rule of ground movement and the settlement of the pile foundation induced by shield tunneling. The main research work and achievements of the paper are as follows:1. The paper works out the subsidence control standards of sand and gravel stratum in Beijing combining with the control standards of ground and pile settlement at home and abroad.2. The paper works out the major influence on stratum deformation caused by the shield tunneling combined with the results of numerical simulation.3. The paper analyzes the deformation and internal force of the adjacent pile foundation induced by the shield tunneling.4. The paper simulates the positional relationship between the pile and the tunnel and divides the pile foundation area influenced by the shield tunnel into A, B, C area. The pile foundation in the corresponding area will be divided into A, B, C class pile accordingly. And referring to the pile settlement control standards, the pile settlement area is divided into a slight impact zone, secondary impact zone, a significant impact and danger zones.5. Through the detailed simulation and research summary of the pile settlement in three kinds of regions under a variety of locations, the paper finally gets zoning schematic of the influence of adjacent pile foundation caused by the tunnel excavation. The schematic can be a reference to discriminate the influence on the pile foundation caused by the tunnel excavation in actual project.6. Analyze the settlement of pile groups caused by the shield tunneling, and compare this with the single pile.7. Summarize various reinforcement methods that can effectively control the settlement of the stratum and the pile foundation caused by shield tunneling in actual project.The work and conclusions of this paper have a good reference value for the safety analysis and evaluation of shield tunneling crossing bridge pile foundation.