饱和黏性土的总强度与基坑工程水土合算土压力 分析方法

Total Strength of Saturated Clay and Earth Pressure in Excavation by Total Stress Analysis Method

摘要:

回顾了饱和黏性土总强度S_u的概念以及“φ=0法”的基本原理，指出直接将三轴固结不排水强度指标c_cu、φ_cu 和直剪固结快剪强度指标c_cq、φ_cq代入朗肯土压力公式是一种错误的分析方法，由此导致了对水土合算土压力分析方法的误解。根据两种试验的原理，推导出了采用强度指标c_cu、φ_cu 和c_cq、φ_cq表示的总强度S_u，进而依据“φ=0法”，给出了基坑开挖卸载下正确的水土合算土压力公式。结合该公式，对行业规范中采用的一些土压力计算方法进行了评述，并结合算例结果对计算分析中几种强度指标的应用进行了评价。

关键词:饱和黏性土;总强度;水土合算;土压力

Abstract:

Based on the review of the concept of total strength S_u and the principle of “ method”, it is pointed out that directly substituting the strength parameters of c_cu and φ_cu by triaxial consolidated undrained shear test, and the strength parameters of c_cq and φ_cq by direct shear test into Rankine’s earth pressure is a uncorrected analysis method. It results in the misleading of the application of the total stress analysis method. According to the principle of the two kinds of test, the formulations of total strength S_u using the strength parameters of c_cu,φ_cu, and c_cq,φ_cq are derived. Then, according to the principle of “ method”, correct earth pressure equations applied to unloading condition in excavation are presented. Based on the new equations, the analysis methods given in several domestic standards or specifications are discussed. Finally, different kinds of strength parameters in earth pressure analysis are evaluated with analysis examples.

Key words:saturated clay;total strength;total stress analysis;earth pressure