Research On Construction Mechanics Behaviour Of A Subway Tunnel Adjacent To Existing Pile Foundation

With the continuous development of China’s economic society and urban populationrapidly expanding,traffic congestion has become a bottleneck which restricts thedevelopment of city.The subway is an important way to solve the problem. However,due tothe restriction to the underground space and the line,line will cross the weak stratum andmunicipal bridge inevitably.The shallow excavation method is very easy to causedisturbance to stratum and change the distribution of strata stress and displacement,whichcan bring the surface subsidence,displacement of the pile,deformation or damage of thetunnel structure. Especially the unreasonable construction method or supporting measureswill bring engineering safety risk and great economic losses.So the research for differentconstruction methods and supporting measures has an important significance for surfacesubsidence and deformation of tunnel and adjacent pile foundation. To analyze theinfluence of different construction methods and supporting measures,paper studies it withthe method of theoretical analysis and numerical calculation and analyzes it with certaincriteria.The paper’s primary content and result as follows.(1) This paper summarizes the domestic and international situation of shallow buriedtunnel’s effect on ground deformation and adjacent piles and summarizes the application ofgrouting in weak stratum. Then paper discusses the basic principles of stratum deformationand pile displacement from the view of construction mechanics. Finally paper studies theconstruction technology and grouting technology and establishes criteria for the surfacesubsidence,the instability of surrounding rock,structural damage,the deformation of pileaccording to specifications,documents and construction experience.(2) The paper establishes three-dimensional calculation model with ANSYS accordingto the tunnel through Fish-Bridge engineering of Lanzhou metro line.Then paper analyzesthe law of ground settlement,plastic deformation of surrounding rock,lining deformation,displacement of pile caused by different construction methods. Finally,paper selects thereasonable method by before analysis and criterion.(3) Based on the selected method,paper studies the influence of the differentexcavation footage on ground surface settlement,plastic deformation of surrounding rock,lining deformation and displacement of pile.With the comparison of differentexcavation footage,paper gets the reasonable excavation footage by the establishedcriterion.(4) After the construction method and excavation footage are selected,the paperanalyzes the influence of the different range of grouting on ground surfacesettlement,plastic deformation of surrounding rock,lining deformation,displacement ofpile.With the comparison of different range of grouting,paper chooses the economic andreasonable grouting range by the established criterion.