| Soil nailing technology has been widely used in deep foundation pit support due to its unique advantages such as speed,convenience and economy.In order to further improve its safety in deep foundation pit engineering,people adopt step-type soil nailing wall support in many engineering practices.As the soil nailing retaining system is composed of soil and retaining structure,and its reinforcement mechanism is relatively complex,the theoretical research on the step-soil nailing wall lags behind the engineering practice,especially the stress and deformation in each stage of foundation pit excavation is difficult to accurately grasp.On summarizing the research achievements of predecessors,this article in baoding city rainwater pump station deep foundation pit engineering,for example,it is concluded that soil slope deformation,the stress and soil nail stress change rule of judging the cascade the factors influencing the stability of soil nailing wall,and combined with the finite element method and principle is compares the calculated values and measured values of foundation pit,to the cascade soil nail wall supporting structure design and construction provide beneficial help,main contents and results are as follows:Through analyzing and sorting out the data,it systematically discusses the development situation of soil nailing support system,summarizes the research status of soil nailing support technology and stepped soil nailing wall,and explains the action mechanism,deformation characteristics and failure modes of soil nailing support.It focuses on the design plan of stepped soil nail wall support,and uses Lizheng software to calculate the overall stability of the pump room on the northeast side of the rainwater pumping station on Lekai Street,Baoding City.According to the geotechnical survey report and support design plan of the foundation pit,the finite element software Midas/GTS was used to establish a three-dimensional finite element model of the foundation pit.The whole construction process was numerically simulated,and the excavation and support stage was analyzed.The variation law of slope top deformation,soil stress and axial force of soil nails,comparative analysis of the influence ofdifferent design factors on the stability of stepped soil nailed walls,and analysis and comparison of safety factors obtained by Lizheng software and finite element software.With this project as the background,the purpose,significance and plan design of construction monitoring are introduced in detail.The six azimuth measurement points of the foundation pit were selected,and the horizontal displacement and settlement of the slope top surface were monitored in real time during the excavation and support stage,and the monitoring results were elaborated and analyzed;By comparing the results of numerical simulation with actual monitoring data,the safety and reliability of the stepped soil-nail wall support design scheme is verified,which is beneficial to guide the construction of foundation pits.Research analysis shows:When excavating to the step,the simulated and monitored values of slope top deformation increase with the increase of excavation depth,and the growth rate reaches the fastest;There is an obvious excavation pressure difference at the steps of the pit wall.The closer to the stress contour,the more obvious the change in the stress gradient;The axial force of the soil nails near the steps is the largest,and there is stress concentration in the front section of the soil nails;After excavation to the step,there is a big deviation between the simulation curve and the measured curve,but the development trend of the curve is basically the same. |
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