将基坑隔水土层简化为一有预压力的受均布荷载的四边固支板 ,假设土体为弹性和理想弹塑性体 ,分别进行了弹性和弹塑性分析 ,以土体不能受拉为条件 ,求出了基坑隔水土层的临界厚度。计算结果比传统方法的计算结果更符合实际情况 ,特别是弹塑性分析所得结果接近真实的临界厚度 ;对于条形基坑 ,所得临界厚度远比传统方法所得结果为低。 The soil-retaining layer of foundation pit is simplified into a four-sided support plate with pre-pressure and uniform load. Assuming that the soil is elastic and ideal elastic-plastic body, the elastic and elastic-plastic analysis are respectively carried out. Conditions, found the critical thickness of soil-resistant soil foundation pit. The calculated results are more in line with the actual results than those calculated by the traditional methods. In particular, the results obtained by the elasto-plastic analysis are close to the true critical thickness. For the strip pit, the obtained critical thickness is much lower than that obtained by the traditional method.