Study On The Foundation Pit Slope’s Instability Mechanism And Treatment Measures

With the rapid development of high-rise buildings and full utilization of underground space, people attached great importance to deep foundation pit excavation and supporting. However, with the deep foundation pit excavation presenting “more numbers, bigger size, deeper depth, more difficulty”, even more, the complex formation structure and the uncertain geotechnical liquid property and irrational design and less standard construction management, slope instability accidents occurred frequently, that also may cause huge economic losses and serious social impact, more seriously, that can cause life or personal injury. So the research of deep foundation pit slope stability is very important.This paper based on the foundation pit slope accident of Nanjiang in Sichuan province, and according to the accident engineering geology, construction method and design plan to analyze the cause of the accident. Using theoretical analysis and numerical simulation to analyze the foundation pit slope deformation failure mechanism and put forward the effective control measures. The main conclusions were as follows:① The accident investigation reported: The groundwater seepage was fatal influencing factors to soil foundation, it reduced the soil shearing strength greatly and increased the horizontal and vertical displacement, which destroyed the soil properties.② With and without considering the groundwater seepage, simulated the stress-strain and change rule when excavating and estimated its stability. Comparing the results of numerical analysis, when considering the groundwater seepage, the simulation result was in accordance with losing stability and failure of slope phenomenon, which can show that groundwater was the main reason of the project accident.③ The numerical analysis results also showed that whether or not considering the groundwater, the max vertical displacement appeared on the slope top. Without the groundwater, the horizontal displacement of excavation slope increased when the excavation depth deepened. The max horizontal displacement was third to fifth- sixth of excavation depth.④ Using the anti-slide pile, combing the soil retaining plate supporting structure,sewerage system, planting protection, which was a comprehensive approach to make the foundation pit slope security and stability.The study can provide reference to the same stability of foundation pit slope.