Key Technology Study On Bifurcated Tunnels Design And Construction Of Underground Throughway Interchange

Bifurcated tunnel is a whole new type tunnel with special structure in urban underground traffic construction. It is made up of main tunnel part, big-arch section for bifurcated tunnel, the double-arch section, the small spacing section and the two-separated tunnels. Bifurcated tunnel coinstantaneously have characteristics of big-arch section, double-arch section and small spacing section, so its structure form and mechanics transform become much complex.However, the construction and research of Bifurcated tunnel are still at the preliminarily stage now, especially lack of systematic and comprehensive research, saying nothing of technology criterion and construction standard, so it is very valuable to study on construction deformation of bifurcated tunnel. Based on the deformation characteristics, the countermeasures of construction technologies are given, the study provides indispensable evidence for the design and construction of the bifurcation tunnel of urban underground interchange.Based on 863 project plan "Construction technology study on underground interchange tunnel" and《Beijing Underground Space Layout》"four longitudinal and two horizontal throughway " write by Programming Committee. People Guard Bureau and City Layout Design Institute, combined with Beijing subway M10 stratum reconnaissance data to build numerical computer model, and study on comparing with subway bifurcated tunnel monitor data, finally take out practicable technology measure to service for design and construction of bifurcated tunnel.In the first part of the thesis, leading introduce the development actuality of city underground throughway in and out of country, especially compare main cross-section,the width of hard strip,the width of side verge,the height of kerb and so on, then bring forward right Beijing underground interchange fork model under principle of safety,practicality,economy and reliability.In the second pare of the thesis, generally study of tunnel computer and construction theory, and build three-dimensional soft-soil tunnel FEM model with fifty meters depth in Midas/GTS,mainly analyze five working procedures of CD method,CRD method,turnoff before or afters small pipe and support procedure and so on, then analyze the sedimentation,maximum/minmum principal stress sedimentation nephogram of secondary lining. Especially study on stress release degree with different working procedures, and then factual effect under adopt different timbering; the influence of key section by steps of different working procedures, at last find out the most dangerous step and take out measures.In the last part, combined with similar Beijing subway projects, compare with computer method and result; make a summary of the adaptive model dimension and the construction procedure for future Beijing underground throughway fork.The research results have strong forward-looking explore, have some instruction and reference to the future relevant projects.