正断层对下盘影响区基坑围护桩变形的影响

Deformation of Foundation Pit Retaining Piles in Footwall Zone Influenced by Normal Fault

为探究正断层对下盘影响区基坑围护桩变形的影响特性,以深圳市某基坑工程为案例,采用数值模拟和现场实测等综合分析方法,分析了正断层对下盘影响区围护桩变形特性及不同断层滑移量、倾角和位置对围护桩变形的影响规律,并对断层参数进行了敏感性分析和正交试验。结果表明:正断层下围护桩的变形减小,减小趋势重心下移,桩身的上部变形影响明显大于下部;桩身变形与断层滑移量、倾角成反比,与断层距基坑的距离成正比,且最大变形变化率r(ΔZ_(max)/Δ)随断层滑移量和倾角增大呈近似指数函数减小,随断层距基坑的距离增大呈近似对数函数增大;通过断层滑移量、倾角和位置对围护桩最大变形的敏感性分析,得到断层倾角影响最大,滑移量次之,断层位置影响最小的结论;通过64组正交试验数据拟合,得到围护桩最大变形U_(hm)与指标η(θπT/180°S)具有良好的线性关系,进而得到正断层对下盘影响区基坑围护桩最大变形的预测模型和该项目预测公式。研究结果可为正断层区域类似地质条件下的基坑工程变形控制提供参考。

To investigate the deformation characteristics of retaining piles in the footwall influenced by normal faults,a case study of a foundation pit project in Shenzhen City was conducted using a comprehensive approach that included numerical simulations and field measurements.The study examined how different fault slip amounts,dip angles,and positions affect the deformation of retaining piles in the footwall’s influence zone.Sensitivity analysis and orthogonal experiments were carried out to assess the impact of these fault parameters.Results revealed that deformation of the retaining piles decreased under the normal fault,with the center of gravity shifting downward.The upper sections of the piles experienced more significant deformation compared to the lower sections.Deformation was inversely proportional to both the fault slip amount and dip angle,and directly proportional to the distance from the fault to the foundation pit.Specifically,the maximum deformation rate,r(ΔZ_(max)/Δ),decreased exponentially with increasing fault slip amount and dip angle,but increased logarithmically with increasing distance from the fault.Sensitivity analysis showed that dip angle had the most significant impact on the maximum deformation of the retaining piles,followed by slip amount,with the fault position having the least influence.By fitting data from 64 orthogonal experiments,a strong linear relationship was established between the maximum deformation U_(hm)and the indexη(θπT/180°S).Consequently,a predictive model for the maximum deformation of retaining piles in the footwall’s influence zone was developed,along with a corresponding predictive equation for this project.These findings offer valuable insights for deformation control in foundation pit projects located in normal fault areas with similar geological conditions.