Study On The Small Curve Shield Adaptability And Construction Characteristics Of ChangSha Wan Jiali Tunnel

Recently,the shield tunnel has been extensively constructed underground the cities.Small curved tunnels have to be used for the restrictions of city planning,dense buildings,pipelines and other obstacles.Based on unique construction characteristic of Wan Jiali small curved tunnel in Changsha,this paper emphasis on the discussion of curved shield adaptation,curved tunnel construction stability and construction control technology by adopting theoretical analyses,numerical calculation and relevant engineering information.The main contents of the research include:(1)Considering the geology and hydrology condition(the pellet gradation number,the stratum category,soil residue processing)of Wan Jiali tunnel,the advantages of two kinds of shield models were compared and analyzed and adaptability of shields and segments to different formations condition and tunnel line were researched.(2)Based on the limit equilibrium theory,the improved model of the silo theory which apply to the small curved shield tunnel was proposed and the minimal supporting force calculation formula considering the influence of groundwater of the tunnel face was deduced,whose reliability was verified by numerical simulation method.Also,the influence of groundwater level,internal friction angle and cohesive force on the limit supporting force was analysis.(3)According to the model analysis of finite element software,the surface subsidence processes of small curved shield tunnel were discussed and the soil deformation law between curved tunnel and straight tunnel were contrasted.Finally,the change trend of displacement under different radius curved tunnel were compared.(4)By intuitionistic analysis and variance analysis of test result based on orthogonal experimental design,sensitivity sorting was conducted by five factors affecting the tunnel deformation on six indicators evaluating the tunnel stability and the construction risk level was evaluated.(5)For the small curved characteristics of shield machine,the difficulty of construction of curved shield tunnel were discussed,and,the axis control technology,integral cornering control technology and segment quality installation technology of small curved tunnel was put forward.