STUDY ON GROUND SUBSIDENCE LAW OF SHIELD TUNNEL CON-STRUC-TION IN KARST AREA

In the process of tunnel construction, underground karst is one of the main causes of ground collapse. In view of the situation that there are hidden karst caves in the soil layer around the shield tunnel, to explore the influence of karst caves on the law of surface settlement, this paper carries out research from the aspects of karst cave shape, different positions and different horizontal lengths by using GTS/NX finite element software. The results show that the lateral ellipse cave is the most unfavorable shape. In the horizontal position, the karst cave is located on one side of the tunnel, especially in the direction of 40°~50°, and the surface settlement increases significantly. There is a "critical clear distance" in the vertical position, which minimizes the surface settlement. When the horizontal length of the cave exceeds a certain value, the surface settlement increases sharply. The surface settlement law obtained by the research provides the basis for the deformation of the stratum where the karst cave is located, the prediction of the accident and the formulation of the treatment scheme.