Stability Analysis Of Composite Support Structure For Deep Foundation Pit

In recent years,with the continuous expansion of human activity space,foundation pit engineering is also developing towards the direction of deep and large,so the stability of foundation pit engineering has higher and more stringent requirements.The stability of foundation pit supporting structure is mostly analyzed and judged by the safety factor method based on the limit equilibrium theory.At present,there is no standardized requirement for the theoretical evaluation system of reliability of foundation pit supporting structure.In the foundation pit supporting structure,the composite soil nailing support structure inherits the characteristics of low cost,easy construction,short construction period,safety and stability of the soil nailing support structure,but also can improve the bearing capacity of the structure,better control of deformation and settlement,can not only meet the safety requirements of the deep and large foundation pit,but also meet the economic requirements.In this paper,the stability of composite soil nailing support structure in deep foundation pit engineering is analyzed by analyzing the stability of foundation pit engineering,calculating the reliability of actual engineering,and combining with the actual monitoring data and numerical simulation.The main research is as follows:(1)By analyzing the working principle of the composite soil nailing wall support structure,the reliability theory is introduced and compared with the stability calculation method of the composite support structure,and the JC method is selected from the commonly used reliability calculation method and applied in the subsequent research.(2)The limit state function was established according to the failure mode of the composite support structure,and the reliability of anti-sliding failure,anti-overturning failure,anti-wedge sliding failure and anti-pulling failure and failure mode evaluation were carried out for the composite support design scheme of the actual project,and the settlement and horizontal displacement of the composite support structure were monitored and analyzed.The results of reliability calculation are compared with the safety factor of the structure and the monitoring data.It is proved that the reliability theory can reflect the safety state of the supporting structure more accurately.(3)Uses the finite difference software of composite soil nailing structure of foundation pit engineering example for three dimensional numerical simulation,obtained during the process of excavation of foundation pit horizontal and vertical direction of the changing law of displacement and soil nail axial force distribution,the simulation results agree with reliability calculation results and monitoring data,and the supporting pile diameter and soil nail length as a variable,Further explore the influence of different supporting structure factors on the stability of foundation pit.