Study On The Construction Mechanics And Scheme Optimization Of Underground Interchange Tunnel

Chao Tianmen underground interchange tunnel in Chongqing, of which the structure is complicatied, the excavation width and height are great and the clean distance is small, is the first large scale urban underground interchange project planned at home and abroad at present. It brings forward not only the challenge of close-spaced construction of underground projects and the anlysis theory of surrounding rock stability, but olso the higher requirement of the construction scheme and control. Therefore, the study on the underground interchange tunnel has important academic and real meaning. This paper mainly study the construction progress of the orthogonal and oblique part of underground interchange tunnel under two construction scheme of the first lower tunnel then upper tunnel. Contents and resulting achievement of this paper are as follow:①The geological condition, hydrogelogical condition and the design technical standards and so forth of the underground interchange tunnel are systematically introduced in the paper.②The general mechanic principle of closed–space construction of underground progress is integrality introduced and the emphasis is on the variation and the impact range of the single cavity and overlapping cavity during the excavation.③By three dimensional simulation and analysis of the construction process of the two schemes, the conclusions indicate that the change tendency of the stress and displacement of surrounding rock and support structures, ground settlement and the distribution range of the plastic zone is concurrent in two formula, but the maximum radis of two tunnels and the displacement of the lower crownis are less small in the scheme that the fist upper tunnel then upper tunnel.④By three dimensional simulation and analysis of the construction process of the two formula,the conclusions indicate that the change tendency of the stress and displacement of surrounding rock and support structures, ground settlement and the distribution range of the plastic area is concurrent in two schemes , also the impact range of the mechanic behavior of the two tunnels is different according to the oblique degree and the excavation width of the two tunnels, but the maximum radis of two tunnels and the displacement of the lower crown are less small in the scheme that the fist upper tunnel then upper tunnel.⑤The displacement and stress of the surrounding rock and the plastic areas of the orthogonal tunnel and oblique tunnel in two schemes, the scheme that the formula first upper tunnel then lower tunnel is more reasonable.The conclusions offer scientific basis for the optimum design and construction of the underground interchange tunnel, and also offer referenced experience for similar projects.