Deformation Monitoring, Numerical Simulation And Optimization Analysis Of Double-row Pile-anchor Supporting Structure Of Deep Foundation Pit

High-rise buildings,large-scale underground engineering and three-dimensional integrated transportation hubs have large scale pits and deep excavation.They are often built in cities with dense population and traffic,as well as complex site conditions.As a new type of effective support,the double-row pile-anchor supporting structure has the advantages of high rigidity,good integrity,strong control deformation,more reasonable pile body force and low construction cost,but more complex mechanical and deformation mechanism.At present,there is little research on double-row pile-anchor supporting structure,especially the anchored double-row pile-anchor supporting structure,which is far from meeting the needs of engineering practice.Therefore,based on the deep foundation pit engineering of three-dimensional integrated transportation hubs of Baotou,in this paper the force and deformation law of double-row pile-anchor supporting structure are studied and analyzed from three aspects of on-site monitoring,numerical simulation and parameter analysis.The main research contents and conclusions are as follows:Firstly,the research status of pile-anchor supporting structure and double-row pile supporting structure are briefly described from theoretical research,experimental research and numerical simulation research.And the problems existing in the study of double-row pile-anchor supporting structure at present are pointed out.Also,the theoretical analysis of the deformation of the supporting structure,the surrounding surface and the bottom of the pit,caused by foundation excavation,is carried out,which lays a theoretical foundation for the following.Secondly,the situation of on-site monitoring is introduced,and the horizontal displacement and vertical displacement of the pile top of the supporting pile,the inclination of the supporting pile and the settlement law of the surrounding area around the foundation pit are analyzed to verify the rationality of the supporting structure.Thirdly,ABAQUS was used to establish a three-dimensional model and numerical simulation was carried out to analyze the deformation law of the foundation pit and the surrounding ground as well as the internal force and deformation law of the double-row pile-anchor supporting structure.The rationality of the numerical simulation is verified by comparing the simulation results with the monitoring results.Finally,by changing the factors such as the spacing of double-row piles,the diameter of double-row piles,the pre-stress,the inclination angle and the length of anchor cable,the force and deformation of front and back row piles are analyzed,and the optimal design of double-row pile-anchor cable supporting structure is carried out.According to the parameter analysis,it is reasonable for this project,with the pile diameter of 1.2 m,the pile spacing of 1 d ~ 2 d,the anchor cable pre-stress of 600 kN,the anchor cable inclination angle of 10° ~ 15° and the length of anchor cable of 24 m.