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在三级法向应力条件下,分别对处于饱和与最优含水率状态时的4种土样进行直剪实验。所得结果表明,基质吸力会转化为土样的一种黏聚力,并以这种形式来增强土样的强度。与此同时,吸力对土样内摩擦角所造成的影响却是很微小的。分别用同种土样来进行持水特性试验,得到了每种土样处于吸湿与脱湿过程时的土-水特征曲线。对土-水特征曲线进行分析后可知,同种土样的强度特征与其所经受的水力路径是息息相关的;另一方面,与饱和土相比,促使非饱和土强度得以增加的因素是多样的,基质吸力只是占主导地位的因素。依据分析所得结果,可将Fredlund等人提出的非饱和土抗剪强度公式表述为更为直观的形式。
Under the three normal stress conditions, the direct shear tests were carried out for four kinds of soil samples under saturated and optimal water content conditions respectively. The results show that the matrix suction can be transformed into a kind of cohesion of soil samples, and in this form to enhance the strength of soil samples. At the same time, the influence of suction on the internal friction angle of soil is very slight. The same type of soil was used to test the water holding capacity, and the soil-water characteristic curves of each soil type in the process of moisture absorption and desorption were obtained. After analyzing the soil-water characteristic curve, the strength characteristics of the same kind of soil are closely related to the hydraulic path it is subjected to. On the other hand, compared with the saturated soil, the factors that promote the strength of the unsaturated soil are varied , Matric suction is only the dominant factor. Based on the analysis results, the formula of shear strength for unsaturated soils proposed by Fredlund et al. Can be expressed as a more intuitive form.