| Due to the rapid development of social economy and urbanization that has occurred in China over the last few years, ground construction and transportation facilities have not been able to meet the needs of social development. Therefor, how to efficiently develop and utilize of urban underground space has attracted more and more attention from academic organizations and governments. Subway tunnels and road tunnel construction is one of the most common underground space development. In order to meet the terrain and the lines, many adjacent tunnel's design and construction come forth endlessly. Planned Liang jiang tunnel at Chaotianmen in Chongqing serving as research background, stability of adjacent tunnel have been analyzed with theoretical analysis, numerical simulation and model test. The research contents and conclusion are as follows:(1) Based on the limit equilibrium theory and variation method, the most dangerous sliding surface of shallow tunnel is studied. The safety factor was defined as the ratio of anti-sliding force to sliding force on the most dangerous sliding surface. According to the instability mode and stability analysis methods of shallow adjacent tunnels, stability analysis method of shallow adjacent tunnel has been studied.(2) According to the relationship between rupture angle and principal stress, the distribution of failure surface in surrounding rock of deep circular tunnel was obtained, which was verified used the variation method. Surrounding rock have been simplified as elastic-perfectly plastic material, then based on sliding surface and critical plastic radius, The safety factor of deep circular tunnel was defined as the ratio of average shear strength to average shear stress on the sliding surface.(3) Deep parallel tunnel has been transformed into half plane with circular tunnel according to the symmetry principle, then multi-connected domain is turned into double connected domain. With mapping function half plane with circular tunnel is transformed into concentric annulus, then deep adjacent tunnel's stress is solved with complex variable function method of elasticity mechanics. Based on the result, the deep adjacent tunnel stability can be judged.(4) On the base of the comprehensive testing system for structure and surrounding rock masses of highway tunnel(CTSSSRH), three-dimensional model test about forked tunnel with different altitude have been carried out. In order to analysis the new tunnel's influence on the existing tunnel, the distributions and changes of surrounding rock pressure, surrounding rock internal displacement and internal force of support structure of the existing tunnel have been metered and analyzed.(5) With finite element software ANSYS, the interaction between old and new forked tunnel with different altitude have been analyzed. the results compared with model experimental results, witch shows that model experimental results are rational. Comparing the numerical simulation results under the condition of different excavation scheme, the reasonable excavation scheme has been studied.(6) The safety factor of shallow adjacent tunnel is calculated with stability analysis method of shallow adjacent tunnel. The strength parameters of surrounding rock are reduced according to these safety factors, then the numerical simulation is used to analyze of shallow adjacent tunnel's plastic zone. The two methods are used to analyze and verify shallow adjacent tunnel's stability.
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