Bearing Mechanism And Structure Optimization Of Sparse Pile And Strong Anchor Supporting Structure In Loess Area

Many deep,large and complex foundation pits have been produced during the development of urban underground space,and the safety and stability of foundation pits have received extensive attention from engineering and academic circles.Pile-anchor supporting structure is widely used in foundation pits,but due to the different loess structure,the interaction mechanism between rock-soil-pile-anchor becomes very complicated and has typical regional differences.Based on this,on the basis of predecessors,relying on the foundation pit project of the Xi’an Xingfu Forest Belt Construction Project,this paper comprehensively uses numerical simulation methods combined with theoretical analysis and on-site monitoring to study the bearing capacity of the pile-anchor supporting structure for deep foundation pits in loess sites.Mechanism,then optimized design of the sparse pile and strong anchor support structure based on the analysis of the sensitivity of support parameters.The main research contents and conclusions are as follows:(1)Numerical simulation and on-site monitoring were used to analyze the force and deformation characteristics of the supporting structure during the excavation of the foundation pit,and the validity of the numerical model was verified.Large,the internal force of the supporting pile body reaches the maximum at 13 m,and it can be inferred that the 13 m buried depth of the foundation pit is the key part of the support.(2)Through numerical simulation and theoretical analysis,the influence of anchor cable pre-stress,length,angle and vertical spacing on the deformation and internal force of the supporting structure is discussed.The results show that when the anchor cable prestress does not exceed 180 k N,increasing the prestress will significantly reduce the internal force and deformation of the supporting structure;when the number of anchor cables increases from 3to 4 rows,the maximum value of the internal force and deformation of the supporting structure decreases The amplitude is not obvious;when the length of the anchor cable is less than 15 m,increasing the length can effectively reduce the deformation of the supporting structure;the installation inclination of the anchor cable has no obvious influence on the supporting structure.(3)Through numerical simulation and theoretical analysis,a reasonable range of pile spacing for the sparse pile strong-anchor supporting structure considering the soil arching effect is put forward.The reasonable pile spacing range is 3.4～4.4 times the pile diameter.At the same time,it is found that as the pile spacing increases,the support The internal force and deformation of the structure also increased significantly.(4)Based on the sensitivity analysis of the anchor cable parameters,the pile-anchor supporting structure was optimized based on the maximum internal force and deformation of the pile body and the engineering cost.The optimal parameters of the current project were determined to be 4 times the pile diameter and 4 rows of anchors.Cable,prestressed 180 k N.