基坑开挖中考虑水压力的土压力计算

CALCULATION OF EARTH PRESSURE ON EXCAVATION CONSIDERING PORE WATER PRESSURE

本文从土的有效应力原理出发,分析了软粘土中深基坑开挖的土压力计算问题,着重讨论了孔隙水压力对土压力的影响.经过分析,作者认为当采用总应力法计算时,原则上应采用卸载强度指标.作者认为以下两个原因使得“水土压力合算法”在软粘土地区的临时性开挖工程中土压力计算值与实测值较接近:一是卸载引起负超孔压,卸载总应力强度指标大于常规三轴加载总应力强度指标;二是渗流引起主动区孔压减小,被动区孔压增大.最后,作者强调不要拖延基坑开挖的进度.

Based on the principle of effective stress, the authors analyzed the calculation of earth pressure on deep excavation. This paper focuses on the influence of pore water pressure on earth pressure. According to the analysis, the authors conclude that the unloading shear strength parameters should be used when applying total stress method. The authors also consider that there are two reasons causing the method of water-soil calculating together popu lar, one is that unloading brings about negative pore pressure, the unloading total shear strength parameters are larger than those of the triaxial loading one; the other one is that seepage makes the pore pressure decrease in the active zone and increase in the passive zone. Finally the authors remind that one should not delay the process of excavation.