Study On Influence Of New Underground Passage On Existing Tunnel Environment And Anti-floating Design

The rapid development of Chinese economy drives the use of urban underground space,especially the rise of subways and rapid development.The excavation of the newly built overlapping underground passage will inevitably affect the surrounding environment and the normal operation of existing tunnels.If the excavation and construction are inappropriate,it will affect the operation of the subway and even cause huge accidents.Therefore,It is necessary to study and analyze the construction of overlapping underground passages,and reducing the impact is very important.Based on the research background of the Pengzu Avenue Overlap Passage Project of Xuzhou Metro Line 2,under complex conditions,more detailed study and discussion of the impact of the construction of overlapping underground passages on its own stability and surroundings.This article mainly includes the following aspects:(1)Analyze the geological and hydrological conditions of the Pengzu Avenue project,propose appropriate excavation methods and technologies,and adopt a construction method that combines the MJS method and the tube-screen method to protect the normal operation of the subway below,and further affect the overlapped underground The construction of the passage carries out the analysis of the risk points in the affected area.(2)For the stability analysis of the stacked-span passage project,The calculation method of the overall stability and soil displacement of the retaining structure of the foundation pit is proposed,and the anti-floating design is carried out and checked.(3)The finite element software GTS is suitable for geotechnical problems,more convenient,and a more practical modified Morcoulomb constitutive model is selected for three-dimensional modeling,and study the impact of complex construction of overlapping underground passages on surface displacement,retaining piles,subway stations and subways in operation.It also analyzes the internal forces of the structure such as the floating problem and the most unfavorable working conditions of Metro Line 2,and adopts measures such as refined partitions and optimized working conditions to reduce the impact of floating.It was found that the pit edge deformation value first increases and then decreases,and eventually tends to a small value.The settlement within 2-15 m near the side of the foundation pit is most obvious.At a distance of 25 m from the outside of the pit,the surface settlement tends to be gentle and the deformation remains small.The depth is about 4-6m,and the pile deformation value is relatively large.As the distance gets farther,the influence value gradually stabilizes.Different construction conditions will cause the deformation of the subway tunnel.When the area above the tunnel is excavated,the maximum value of the subway float is 2.445 mm.After the optimized design,the maximum value is reduced to 1.627 mm.(4)Using the method of on-site measurement to monitor the overlapped channel project and the surrounding environment,draw the result data into a curve,so as to conduct comparative analysis.Because the numerical simulation cannot be accurately simulated,the simplified processing is carried out,and Without considering the impact of groundwater,the monitoring and drawing results are slightly larger than the simulated ones,and are basically the same on the whole.