Analysis of settlement and deformation of subway double line shield beneath existing railway roadbeds

Abstract In order to study the settlement and deformation characteristics of the existing railway roadbed during the continuous underpass of the existing railway under the construction of the double-line shield tunnel, based on the continuous underpass of several existing railway projects of Changzhou City Railway Line 2, the two-dimensional and three-dimensional finite element methods of Plaxis2D and ANSYS were adopted. The roadbed settlement and deformation law of high-speed railway which adopts the pre-reinforcement technology and the railway which does not adopt the pre-reinforcement technology are analyzed and studied respectively. The two-dimensional simulation results show that the roadbed settlement of the unreinforced high-speed railway is much greater than that of the pre-reinforced high-speed railway, but there is little difference in the tunnel arch settlement between the two. The three-dimensional results show that the soil around the middle switch is greatly affected by the displacement and deformation of the adjacent switches. The maximum settlement of the high-speed railway roadbed after reinforcement is 0.69 mm, while the maximum settlement of the high-speed railway without reinforcement is 7.8 mm. The advanced pre-reinforcement technology can effectively reduce the settlement of the railway roadbed in the construction of the existing railway, and reduce the interference of the adjacent soil in the construction of the shield. In this paper, the settlement and deformation rule of double-line shield tunnel under the existing railway roadbed is revealed, which can provide scientific basis for the design and construction of similar projects.