Analysis Of Settlement In The Test Section Of Dalian Subway Line One Which Is Across The Cave

With China’s fast development of tunnel traffic, it is common for tunnels to encounter large soil-filled caves. The test section of Dalian subway line1meets with huge filled cave and when it runs across the cave, differential settlement must be treated seriously as it can cause cracking of tunnel lining and leakage.The soils filling the cave are always of great variety and complicated with high water content and high modulus of compression. When the tunnel run through the cave, it has to pass from the rock foundation segment to the soil foundation segment and the two different foundations vary enormously in modulus compression. With the modulus of the soil foundation much smaller than the rock foundation, difference in tunnel settlement which always cause cracking of tunnel lining and leakage between the two segments are two much that it cannot be ignored.In this paper, at first the Winkler elastic foundation model is being used to calculate the settlement of the tunnel in the soil foundation segment. By simulating the tunnel as a beam with longitudinal stiffness on elastic foundation and two ends of the beam embedded in rock while it bears the self load of the tunnel structure and filling soils above it, the analytic solution of settlements is obtained.In the second the numerical solution is obtained by using the ANSYS software under the assumptions that the tunnel and soils are behaving as liner elastic materials.After that the limitations and applicability of two kinds of solutions are discussed. For further study, changing of settlement is calculated when we change the kinds of soil filling the cave, then we modeled the changing rules when the length of the filled cave along the tunnel and the depth of soils below the tunnel bottom are changing separately.At last how the settlement varies is observed when the longitudinal stiffness of the tunnel is discounted.When the elastic foundation beam model and tunnel longitudinal stiffness of Homogeneous concrete beam are applied in the analysis of the differential settlement of tunnel segments across the filled cave, conclusions of this thesis are as below:Firstly, the maximum value of settlement happens in the middle of the tunnel segment across the filled cave. Secondly, the settlement is proportional to the length of the cave along the tunnel and inversely proportional to the tunnel longitudinal stiffness and the modulus of filling soils.