考虑水位和孔压影响的基坑抗隆起稳定性上限分析

Basal-heave stability of excavations considering groundwater level and pore water pressure fluctuations by upper bound method

分析了基坑围护墙内外水位和孔压的分布规律,基于极限分析上限定理,将孔压做功作为外力功代入上限定理能量平衡方程,选用Prandtl滑动模式建立了考虑地下水位和孔压影响的基坑抗隆起分析方法及其验算公式。通过该计算方法对坑外水位、土体强度、硬土层深度和基坑开挖宽度等参数的影响分析以及工程实例的对比计算,验证了公式的适用性。分析结果表明,基坑内外水位和孔压变化以及地下水渗流对抗隆起稳定性产生重要影响,地下水是影响基坑稳定性的一个重要的不利因素。与经典的Terzaghi、Bjerrum和Eide方法以及Chang方法相比,该分析方法可以考虑坑内外水位和孔压对抗隆起稳定性的影响,为软土地区基坑抗隆起稳定性分析提供了合理的计算方法。

The groundwater level and pore water pressure distribution of retaining excavation were analyzed based on the upper bound theorem.The work of water pressure was introduced into the upper bound work balance equation as external loading,and the Prandtl soil slip mode was chosen to analyze basal-heave stability of excavation considering groundwater level and pore water pressure changing.In addition,the effects of the groundwater level,soil strength,location of hard stratum and width of foundation pit on the basal-heave stability coefficient were discussed;and two practical cases were calculated to verify calculation formula applicability.Analysis results show that the groundwater level and pore water pressure influence basal-heave stability;and groundwater is an important adverse factor of excavation basal-heave stability.Comparing with Terzaghi＇s method,Bjerrum Eide＇s method and Chang＇s method,calculation method of this paper can reflect the influence of groundwater level and pore water pressure on basal-heave stability;and it provide a reasonable calculation method of excavation basal-heave stability in soft soil.