The Application And Numerical Simulation Analysis Of Pile-anchor Reinforcement System In Foundation Excavations

In recent years,with the rapid development of economy in our country,constantly improve the level of urbanization,a shortage of urban land resources is increasingly highlighted.The rapid rise of the real estate,municipal engineering and tunnel engineering,combined with the limitation of city ground space using range,make more engineerings toward underground space development,there is a underground malls, underground parkings, subway stations, underground tunnels and a series of underground engineerings construction,the excavations numbers increasing more highly,Involving field expands growing very fast,complexity and difficulty also will increase of foundation pit.The foundation pit engineerings is large quantity, more difficulties, high risks of key engineering projects in construction projects.In the foundation pit,design and construction should not only ensure the safety of the supporting system in the construction processing,in the same time, control deformation of the structure and the surrounding,to ensure the safety of the surrounding environment.The application and rapid development of pile-anchor supporting structure is beginning in the 1980 s,now has become a more mature, is also a common form in our current application of foundation pit supporting.As the excavation depth deepening,the excavation environment increasingly complex and Frequent occurrence of foundation pit collapse.This not only influence the construction period and at the same time will increase the cost of the construction cost price.As a result,In order to make the foundation pit achieve the goal of safe and effective in buildings and structures, need for real-time monitoring of foundation pit engineering,through feedback by actual monitoring data of foundation pit in the actual state of the changes in the construction,ensure the safety of the foundation pit.With the development of science and technology,the computer has now been applied to various fields,numerical analysis and numerical simulation has been widely used in foundation pit.By using numerical simulation method for retaining structure is analyzed,can better induction factors of the excavation and supporting.This paper combined with specific engineering example-JiangXiGuoGuangcity complex foundation pit,to design,simulate analysis and field monitoring of the excavation in pile-anchor supporting system.Combining with engineering survey, engineering geological conditions, the surrounding environment factors and various schemes of the project cost,comparison of different support scheme,to select the best supporting scheme is supporting piles and anchor-cable and high-pressure rotary jet grouting pile joint support form.Using the FLAC3 D Software,by setting the model size and boundary conditions,to determine the initial stress condition and choice of constitutive model,establish numerical simulation analysis model.Through before and after the maximum unbalanced force of the excavation simulation,final calculate the convergence.Through the simulation of pile body internal force to get maximum axial force,shear,bending moment respectively:2.649×105N、2.956×105N、9.058×105N.m,for the theoretical calculation results:2.62×105N、2.59×105N、8.78×105N.m,the results are basically identical. Through simulation of anchor cable internal force get the maximum axial force is 3.851×105N,and the settlement result is 3.6×105N,the results are basically equal.Through simulation of displacement of pile top it is concluded that the total settlement displacement on the top of the pile is 27.7mm,horizontal displacement is 35 mm,both conform to the requirements of the specification.Through the simulation under the condition of with and without supporting supporting of foundation pit,in the process of each step excavation soil horizontal displacement,horizonal internal force, vertical displacement and vertical internal force of contrast,under the condition of shallow foundation pit in excavation,internal force and displacement variation of soil are almost the same.But with the increase of depth,under the condition of no support,cause of foundation pit slump,and when there are supporting change is small,explain the pile-anchor supporting system to ensure the safety of the foundation pit.According to the engineering actual situation,set the specific monitoring plan,monitoring the displacement of pile top settlement,building subsidence displacement, water level change and displacement of deep soil around the foundation pit.By monitoring,in the foundation pit four side, pile top final settlement10.39 mm,the maximum sedimentation velocity 0.65 mm/d.Building subsidence final displacement14.61 mm,the maximum sedimentation velocity 0.63 mm/d.The water level around the foundation pit basic keep elevation between 81-82 m.The displacement of deep soil 14.36 mm.The above data are in the range of early warning value, foundation pit in the security state.Through monitoring displacement value and the simulation values are compared the displacement of pile top settlement.The changes in the basic are the same.