| Deep foundation pit projects are mostly located in the urban areas with dense buildings and underground pipelines Criss Cross.In order to reduce the influence of foundation pit excavation on the surrounding environment,the deformation and stability of the foundation pit must be strictly controlled.Considering the safety of foundation pit and the complexity of geological conditions,the retaining structure of side wall of foundation pit usually does not use single supporting structure,but adopts combined support system,and the pile anchor supporting combined support system is widely applied.In this paper,after the introduction of the relevant theoretical research on pile anchor and oblique bracing system,taking the foundation pit supporting project of Jing-ao Plaza in Chaoyang Road of Huainan as the background,combined with the engineering example to establish the finite element model.The change regulation of the horizontal displacement of the supporting pile and its internal force,the axial force of each layer and the axial force of the oblique bracing are analyzed in the process of foundation pit excavation.Then the field measured data and the numerical simulation results of the combined supporting system is compared and analyzed to verify the rationality of the numerical simulation process.Finally,through the study of oblique bracing and anchor support parameters on the internal force of the combined support system,analysis of the deformation coordination characteristics of the combined support system,optimizing these support parameters,and the interaction of anchor and oblique bracing is studied in the process of deformation,and the conclusions are obtained,which provides an important reference for the design and construction of deep foundation pit engineering.The main conclusions are as follows:(1)Using the Midas GTS NX finite element software to establish the model,the change law of the horizontal displacement and internal force of the supporting pile body in the excavation of the foundation pit is analyzed.With the excavation of the foundation pit,the axial force of the anchor is basically reduced in the direction of the front end of the free segment and the end of the anchorage section.The axial force of the oblique bracing is closely related to the deformation of support structure at support point.(2)The analysis shows that during the process of foundation pit excavation,the deformation trend of the top of each supporting pile is basically the same,and the axial force of anchor is also increasing,while the axial force of diagonal brace decreases gradually,and the decreasing trend is more obvious.The numerical simulation results of the horizontal displacement of the pile top are basically the same as the monitoring data under various working conditions,indicating that the numerical simulation of the combined supporting system is reasonable.(3)Different oblique bracing and anchor parameters have different influences on the internal force of the combined support system.The influence of these parameters on the axial force of the first layer anchor and the oblique bracing force is limited.The change of the axial force of the oblique bracing and anchor is closely related to the deformation of the supporting pile body.(4)There is a difference in the horizontal deformation of the pile body under different oblique bracing and anchor parameters,this difference is closely related to the interaction between oblique bracing and anchor.The change process of axial force of oblique bracing and axial force of anchor is the process of deformation coordination of combined support system,that is,the change of horizontal displacement of support pile body affects the bearing capacity of supporting piles,anchor and oblique bracing. |
