基坑开挖扰动变形特征及控制效果模拟分析

Simulation Analysis of Disturbance Deformation Characteristics and Control Effect of Foundation Pit Excavation

坑中坑的开挖对于基坑的稳定性有诸多方面的影响,内坑的开挖会造成土体回弹,引起基坑土体抗力的损失,降低基坑的整体稳定性。运用FLAC^(3D)对合肥恒大中心C地块坑中坑式基坑进行了开挖与支护模拟,计算采用摩尔-库伦本构模型,通过模拟计算得出了基坑应力、桩基应力、桩锚应力,验证了基坑中外坑和内坑最易失稳破坏区域,并对利用负泊松比(negative Poisson s ratio,NPR)锚索对该类基坑进行加密支护的控制效果进行了评价。通过施加位移监测得到了不同开挖阶段基坑地表位移、坑中坑底部位移、以及坑中坑周围土体位移,确定了基坑极易发生破坏的区域以及滑动面位置,建立了坑中坑物理模型,并验证了数值模拟的正确性,研究结论可为类似工程条件基坑的开挖及加固提供理论支撑和实践基础。

The excavation of the pit in the pit has many effects on the stability of the foundation pit.The excavation of the inner pit will cause the soil to rebound and the loss of the soil resistance of the foundation pit,and reduce the overall stability of the foundation pit.FLAC^(3D)was used to simulate the excavation and support of the pit-type foundation pit in the C block of Hefei Evergrande Center.The Mohr-Coulomb constitutive model was adopted during the calculation.Through the simulation calculation,the foundation pit stress,pile foundation stress and pile anchor were obtained.The most unstable and damaged areas of the outer and inner pits of the foundation pit were verified,and the control effect of the use of negative Poisson s ratio(NPR)anchor cables for densified support of this type of foundation pit was evaluated.Through the applied displacement monitoring,the ground displacement of the foundation pit,the displacement of the bottom of the pit in the pit,and the displacement of the soil around the pit in the pit were obtained through the applied displacement monitoring,and the areas where the foundation pit was prone to damage and the position of the sliding surface were determined.The physical model of the pit in the pit was established,and the correctness of the numerical simulation was verified.The above research can provide theoretical support and practical foundation for the excavation and reinforcement of foundation pits under similar engineering conditions.