考虑应力路径基坑变形计算及支护性能研究

基于半无限大弹性空间在条形荷载作用下应力的Melan解,首先根据基坑开挖过程应力状态的变化,建立基坑开挖问题的平面力学分析模型。利用Duncan-Chang曲线模型中的参数计算方法,推导加载和卸载模量公式,进而结合平面应变问题的物理方程和几何方程,建立平面应变问题的本构方程,得到基坑开挖后土体位移计算方法。然后建立土压力与支护结构位移的正弦和幂函数关系曲线,提出土压力计算方法。最后将理论成果应用于工程实践,将土体位移和土压力的理论值与实测数据进行对比分析。研究结果表明:该计算模型得到的基坑变形位移与实测结果吻合较好,验证了土压力与位移计算方法的合理性,同时由监测数据得到锚索预应力随时间的三阶段变化趋势,以及深层水平位移和坡顶竖向位移的匙形分布特点。

Deformation calculation and supporting performance of foundation pit considering stress path

Based on the Melan’s solution of stress and displacement of semi-infinite elastic space under strip load, the plane analysis model of foundation pit excavation was established according to the change of stress state in the excavation process. By using the parameter calculation method of Duncan-Chang curve model, the modulus formula was deduced. Then, the calculation method of soil displacement after foundation pit excavation was established by combining the physical equation and geometric equation of plane strain problem. The curve of sine and power function between earth pressure and displacement of supporting structure was established and the method of calculating earth pressure was proposed. Finally, the theoretical results were applied to engineering practice, the theoretical value and the measured data were compared and analyzed, and the deformation law of foundation pit excavation was summarized. The results show that the deformation of the pit obtained by the calculation model are in good agreement with the measured results, and the rationality of the calculation method of earth pressure and displacement is verified. At the same time, the monitoring data shows the three-stage trend of anchor cable prestress with time is obtained, as well as the spoon shape distribution characteristics of the deep horizontal displacement and the vertical displacement of the slope top.