The Research About Controlling Factors Of Ground Surface Settlement When Line 2 Of Hefei Metro Run Across Under Wulidun Overpass

At present,China's urban underground track construction is mainly shielded construction,its convenient,has a very good safety and wide applicability,has been a lot of use to the underground tunnel construction process.Although the use of shield construction technology has become more mature,but the shield tunnel excavation caused by surface subsidence and the deformation of the surrounding buildings is still we must face the problem.Excessive ground subsidence and deformation of the building pile foundation will seriously affect the service life of the building,but also to the shield tunnel construction to bring security risks.Therefore,how to minimize the soil disturbance caused by shield tunnel excavation and minimize its influence on the ground and adjacent buildings is an important issue that needs further study in the project.Based on the actual engineering of Hefei MTR Line No.2 tunnel crossing Wulidun overpass,this paper refers to the geological prospecting report of the relevant site and the reinforcement scheme of the overpass bridge pier.The finite element software is used to carry out the whole process of the construction of the tunnel The numerical simulation is carried out,and the control factors of surface subsidence of Wulidun overpass are analyzed and compared with the measured data.Specific research content has the following aspects:(1)According to the relevant highway bridge and culverts and the Wulidun overpass bridge pier reinforcement scheme,the bearing capacity limit and the maximum crack width limit are taken as the control standard respectively,and the upper part of the bridge is checked by the relevant computer software,Thus proposed bridge settlement control value.(2)According to the construction progress of the interval shield tunnel crossing the overpass,a set of realistic monitoring scheme is adopted,and the field monitoring data for nearly one month are summarized.Through the analysis of the on-site monitoring data,And the settlement control values obtained by checking the superstructure of the bridge are compared and analyzed to verify the rationality of the bridge upper structure checking.(3)Using the finite element software to simulate the whole construction process,the deformation law of the strata and the adjacent bridge foundation during the excavation of the shield tunnel is studied.At the same time,the superstructure of the bridge is loaded step by step,The effect of different grouting pressure and different soil pressure on settlement is proposed,and the optimized parameter range is proposed.