相邻深大基坑安全距离理论分析与数值模拟

以两相邻深基坑为工程背景,采用极限平衡理论和平面滑裂面假定,对坑间有限土体建立了土压力计算模型。推导出考虑桩土摩擦、土质参数、坑间超载、基坑间距、邻近基坑支撑轴力等因素的主动土压力计算公式,给出了土压力保持不变时的基坑间距,即安全距离b的表达式。参数分析表明:安全间距b随两相邻基坑的开挖深度、桩土摩擦系数的增加而增大,随土体内摩擦角的增大而减小。接着采用PLAXIS有限元软件选取HS本构模型建立两相邻基坑数值模型,对安全距离的各影响因素开展了规律性研究,分析了不同基坑间距下土压力的数值解与本文理论解沿挖深的分布规律,发现二者有较好的吻合性,进一步验证了本文理论的合理性。

Theoretical Analysis and Numerical Simulation of Safe Distance of Adjacent Deep Foundation Pits

The two adjacent deep foundation pits are used as the engineering background. Based on the limit equilibrium theory and plane slip surface assumption, the earth pressure calculation model for the limited soil between foundation pits is established. Which considered the factors such as soil friction, soil parameters, surcharge and spacing between two adjacent excavations and the support shaft force of adjacent excavations. On this basis, the safe distance of adjacent foundation pits b is deduced when the finite earth pressure remains unchanged. The parameter analysis shows that the safety distance b increases with the excavation depth of two adjacent foundation pits and the friction coefficient of pile-soil, while decreases with the increase of the soil friction angle. Next, two adjacent foundation pits numerical models are established to study the influence factors of safety distance by using PLAXIS finite element software and HS model. The numerical analysis of earth pressure under different spacing and the distribution rule along foundation depth compared with theoretical solutions are analyzed. We can find that the results of the two methods have a good agreement. It shows that the rationality of earth pressure theory is reasonable in this paper.