| Along with economic development,urban population expansion causes urban traffic increasingly congestion,for seeking to save space and the requirements of small environmental impact,it is stepping up to the development of underground space and the construction of underground transit in many big cities.At present,Hefei is also in the period of construction vigorously,and the construction of the lake city has attracted many people from all over the world to work live and investment in Hefei.However,the expansion of the population lead to traffic congestion,which make commuting travel peak of the miserable people,so the construction of the subway is a lot of Hefei people’s expect.As the urban underground engineering is often in a busy area with dense populated and skyscrapers,which make nearby and cross subway lines appear.When two tunnels is nearby,even cross with each other,the excavation of cross tunnels easily leads to excessive deformation subsidence of surrounding rock with the soil strata of Hefei accompanied by basically clay and some expansive soil.In order to guarantee the engineering quality and construction safety of cross tunnel construction,safe and effective forepole supporting and secondary supporting measures and corresponding calculation method should be taken to control the surface subsidence.There also should have corresponding calculation method for the surface subsidence and the settlement monitoring of surrounding rock deformation amplitude in cross shield interval,so that the surface subsidence and deformation of surrounding rock in amplitude are in control within the scope of the reliable to ensure safety construction.Based on the engineering background of high-speed rail station cross shield interval of the metro line 1 and line 5 in Hefei,the different cross shield interval strata reinforcement methods and construction technology are discussed in this paper,and the relevant conclusions are produced through the analysis of land subsidence caused by excavation the deformation and stress form.Through the numerical simulations by MIDAS software and the comparison of monitoring data and software simulation data,the reliability of the numerical simulation of MIDAS software is discussed.Also,under the condition of the cross shield intervals,through the numerical simulation of the cross shield interval model,analysis of the function and effect of jet grouting pile formation reinforcement scheme.And by changing the use of jet grouting pile ground grouting surrounding rock parameters of soil properties of the two variables: the soil elasticmodulus and Poisson’s ratio,further simulation study ground grouting surrounding rock stability influence cross shield interval factors.In this paper,the study found that:1.The cross shield interval excavation will lead to deformation of surrounding rock,the closer distance,the greater the influence of tunnel excavation on the upper tunnel,the greater the effect on the stability of surrounding rock.2.Jet grouting pile reinforcement increases the cross shield interval of stability of surrounding rock,reduced the strengthening the regional land subsidence caused by tunnel excavation,reduced the upper tunnel vertical deformation caused by tunnel excavation.3.Under the conditions of using jet grouting pile reinforcement,when the elastic modulus of soil surrounding rock increases,the influence of tunnel excavation on ground settlement decreases,the lower the shield tunnel construction on upper existing tunnel subsidence deformation influence also decreases,and accordingly improve the stability of surrounding rock.4.Under the conditions of using jet grouting pile reinforcement,when the Poisson’s ratio of soil surrounding rock increases,the influence of tunnel excavation on ground settlement increases,the lower the shield tunnel construction on upper existing tunnel subsidence deformation effect also increases accordingly,the stability of surrounding rock. |
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