非饱和黄土土水特征及其强度指标

以多种理论模型对非饱和土三轴仪实测数据进行了拟合评价;并在此基础上,引入非饱和土最新理论,反演和解析了土体脱湿与吸湿条件下的边界土-水特征曲线、渗透系数函数以及吸应力特征曲线;进一步从强度本构入手,结合不同基质吸力的三轴剪切试验结果,探究了基于吸应力的强度特性。研究结果表明:非饱和土三轴仪所测数据点及其三种模型拟合曲线均落在水力边界曲线(SWCC、HCF、SSCC)范围之内,表明了试验结果的正确性和合理性,以及非饱和土中水分的能量和数量的关系因路径差异而具可变性,即基质吸力不再是含水率的单值函数,而是一个范围体系;同时采用吸应力特征曲线的统一有效应力原理来描述土体在非饱和条件下的抗剪强度性质是合理的、普遍有效的,并且验证了土体处于饱和或者无基质吸力时,吸应力不为零,此时的吸应力对应的是土体在剪切破坏时的表观粘聚力这一结论。

Soil-water Characteristics and Strength Indexes of Unsaturated Loess

Studies on soil-water characteristics and shear strength of unsaturated loess have a great significance to prevent and reduce natural disasters of the Loess Plateau. Considering the diversity of soil-water models, several theoretical models were used to fit and evaluate the measurement data of triaxial test apparatus. On this basis, the boundary soil water characteristic curve, hydraulic conductivity function and suction stress characteristic curve were inversed and analyzed under drying and wetting conditions with the latest theory of unsaturated soil. Furthermore, in view of the constitutive relationship, strength characteristics were studied based on suction stress using triaxial shear testing results under different matrix suctions. The results show that the data points measured by the triaxial test apparatus and three corresponding model fitting curves fall within the range of the hydraulic boundary curves (SWCC, HCF and SSCC), which indicated that the test results are correct and reasonable. The results also indicated that the relationship between the energy and the quantity of moisture in unsaturated soils is variable due to path differences, that is, matrix suction is no longer a single-valued function of water content, but a range system. Meanwhile, it is reasonable and generally effective to use the uniform effective stress principle of the suction stress characteristic curve to describe the shear strength properties of unsaturated soil. It is also verified that the suction stress is unequal to zero when the soil is saturated or without matrix suction; the suction stress at this time corresponds to the apparent cohesion of soil at shear failure.