基于非饱和土理论,通过非饱和土直剪试验、 三轴UU、CU和CD试验得出非饱和土的强度指标,对比分析了不同试验条件下石家庄地区非饱和土抗剪强度指标及其在不同基质吸力条件下的变化规律.试验结果表明:石家庄地区抽气饱和后原状土UU试验测得的黏聚力大于直剪快剪试验结果,内摩擦角相差不大;原状非饱和土样UU试验的黏聚力约为抽气饱和后土样黏聚力的2倍,说明该区域非饱和原状土中存在的基质吸力对土样黏聚力的提高贡献较大;土的有效内摩擦角φ′基本不受基质吸力的影响,但随着基质吸力的增加,与基质吸力相关的内摩擦角φb呈非线性增长;试验土体总黏聚力c1′随着基质吸力的增大而呈线性增大.对比结果说明石家庄地区采用抽气饱和后原状土体的UU试验强度指标进行工程设计,在安全性和经济性方面均有一定的优势.如果采用非饱和原状土UU试验强度指标,则需要考虑工程实际中基质吸力受场地及气候等因素的影响.%Based on the theory of unsaturated soil, the strength indexes of unsaturated soil are obtained through direct shear test, UU, CU and CD triaxial test. The strength index of unsaturated soil in Shijiazhuang under different test condi-tions and its change rule under different matrix suction conditions are contrastively analyzed. Test results show that the co-hesion measured by UU test of undisturbed soil in Shijiazhuang are larger than that of direct shear test, and there is little difference in internal friction angle. And the cohesion of unsaturated undisturbed soil samples in UU test is about 2 times that of saturation soil samples. It shows that the matrix suction in the unsaturated undisturbed soil has a greater contribu-tion to the increase of cohesion. The effective internal friction angle of soil is basically not affected by the matrix suction, but another internal friction angle associated with the matrix suction increases nonlinearly with the increase of matrix suc-tion. The total cohesive strength of the soil in the experiment increases linearly with the increase of the matrix suction. The comparison results show that the UU test strength indexes of the saturated undisturbed soil in Shijiazhuang have their ad-vantages in the aspects of safety and economy when used for engineering design. If the strength indexes of unsaturated undisturbed soil UU test are used, we need to consider that the substrate suction in engineering practice is affected by fac-tors such as site and climate.
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