Infiuence Of Different Approximities Of Overiapped Tunneis On Rock Pressure And Lining Mechanical Behavior

Restricted by special land forms, geology, and combined factors of the route's level, longitudinal and lateral data, tunnel approximities and overlapped tunnels will be constructed inevitablely. The differences of approximities have different influences on the force of tunnel structure, displacement and rock pressure. The analysis of influential regularities of different approximities can offer the reference to the design and construction of tunnels. Based on the Xinmeihua Mountain Tunnel on Mitigation Line of Nei-Kun Railway and the overlapping project of Wumeng Mountain Tunnel on Liu-Zhan Line, this thesis sets up three-dimensional finite element models of surrounding rock and tunnel structure by ANSYS, and explores the regularities of variation and distribution of the rock pressure, displacement and structural pressure of overlapped tunnels through the numerical modelling.Through setting up different finite element models of overlapped tunnels under different approximities, this thesis analyzes the rock pressure, lining internal structural force and the lateral and vertical tunnel displacements of Xinmeihua Mountain Tunnel and Wumeng Mountain Tunnel under seven kinds of height differences of two tunnels' rail surfaces: 11.26m, 12.26m, 13.26m, 14.26m, 16.26m, 18.26m and 21.26m. The variation regularities of rock pressure, lining displacement, moment of flexion, and shaft force under different approximities have been concluded by comparing and analyzing the data.The following findings can be concluded from the results of analog computation: rock pressure at the overlapping point can be released to a certainty; the tunnels tend to deform to the close tunnel; lining shaft force and moment of flexion becomes a little asymmetric; and with the increase of level interval between Xinmeihua Mountain Tunnel and Wumeng Mountain Tunnel, the internal force becomes obviously asymmetric, and the maximum change value occurs at the link of the two tunnels' center or at the vertical direction. With the approximity increasing, the release of rock pressure at the overlapping point is decreasing, two runnels tend to bend to the close tunnels, and the asymmetry of lining shaft force and moment of flexion is reducing. The research results will contribute not only to the evaluation of lining internal structural force of overlapped tunnels but also to the improvement of design theory of railway tunnel structure.