3D Numerical Analysis Of Ground Surface Settlement Induced By EPB Excavation

Currently, Tunnel Shield Machine has become an important subway construction method in China. Especially in the soft soil or places with bad geology condition like faults, broken surrounding rocks, Tunnel Shield Machine is widely used. However, in many large cities, Tunnel Shield Machine construction will cause strata deformation and ground surface settlement and bring damage to the underground pipelines, equipments and neighbor buildings. Due to the complicated situation with boundless factors to be considered, there is a great gap between theoretical research and engineering practice. This paper mainly focuses on the ground surface settlement which results from Tunnel Shield Machine construction when doing the research about the influences of environment caused by Tunnel Shield Machine construction method.Earth Pressure Balance (EPB) driving excavation will disturb the surrounding soil and rock, cause the ground loss which result in ground surface settlement, and bring damage to the neighbor constructions, underground equipment. This paper uses FLAC3D to simulate tunnel construction and analyzes the principles of ground surface settlement induced by shield driving construction based on NO.3line subway in GuangZhou. This paper mainly discusses the characteristics of ground surface settlement with respect to the lateral extension of settlement as well as longitudinal section of tunnel and various factors such as earth pressure in cutter chamber, concrete lining support, soil stress release and so on. Calculated by analyzing the following conclusions.1. With the continuous advance of the shield tunnel stratum settlement gradually extended from the top of the tunnel to the surface, the surface settlement is less than the settlement of the tunnel arch. Surface subsidence rate also gradually stabilized with the advance of the shield13.5m at the excavation face. Imposed on the working face of the soil compartment pressure is greater than the formation water and earth pressure shield excavation will result in surface soil excavation in front of uplift, but it is not the overall heave.2. Sink and the bottom of the floating cloud images in the upper part of the tunnel is basically symmetrical, but the range of sinking and sedimentation value than soil floating.3. Surface cross-sectional settlement with the shield driving and continuous outward expansion of the settlement depth increasing. Expansion curve tunnel axis is the axis of symmetry, the tunnel axis at the stratigraphic sedimentation value. Surface subsidence along the axis of each cross-section difference between the larger amplitude of change is not the same. But basically the same overall variation was similar to the normal distribution, and Peck settlement trough.