A large number of experimental results show that there are significant differences between value of classic water-earth press are calculated by classic theories and results measured with engineering, especially in soft soil. Based on analyzing of water-earth pressure, pore water pressure and ground water level during excavation, the varying laws of water-earth pressure, earth pressure, pore water pressure with the conditions and time are described. The estimation formula of earth pressure coefficient after excavation of foundation pit and falling Ground water level, and the estimation formula of pore pressure coefficient before-excavation are given. By analyzing,the effective stress principle also applies to clay. In theory, water-earth pressure should be separate in soft soil. However,the pore water pressure and earth pressure are changing with the time and conditions,accurate calculation is difficult. After considering the various factors influencing the water and earth pressure, an empirical formula of water-earth press on supporting structure is given.%大量的实测结果表明,经典理论计算出的水土压力值与工程实测存在着很大的差别,在软土地区尤为明显.本文通过对基坑工程的实测水土压力、孔隙水压力和地下水位的分析,阐述了基坑外侧水土压力、土压力、孔隙水压力随工况、时间的变化规律,给出了开挖、降水后基坑底面以上的土压力系数估算公式,基坑开挖前的孔隙水压力系数估算公式.通过分析认为有效应力原理同样适用于粘性土,从理论上来讲软土地区也宜采用水土分算,但考虑到孔隙水及土压力随时间、工况不断发生变化,精确计算十分困难,在综合考虑影响水土压力的各种因素后,给出了作用在支护结构上的水土压力合算经验公式.
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