含裂隙红黏土土水特征与强度特性研究

红黏土边坡在干湿循环作用下极易产生裂隙，裂隙发育将对土体水力学特性及强度造成不利影响，从而降低边坡稳定性。以长沙红黏土为研究对象，制备具有不同裂隙数量的红黏土试样，开展了渗透试验、土水特征曲线试验和直剪试验，揭示了红黏土饱和渗透系数、土水特征曲线和抗剪强度指标随裂隙数量和干密度的演化规律，建立了相应函数表达式。结果表明：红黏土渗透系数量级为10^-5～10^-7 m/s,饱和渗透系数随干密度的增加而减小，随裂隙数量的增加呈指数型增长，裂隙增加5条，饱和渗透系数提高66.4倍；干密度低和裂隙数量多的试样饱和体积含水率更高，脱湿过程中体积含水率随基质吸力降低速率更快，残余含水率更低，持水能力更差；红黏土抗剪强度指标与干密度呈正比，与裂隙数量呈反比，当干密度增加0.28 g/cm³,黏聚力和内摩擦角分别提高2.35倍和0.94倍，而当裂隙增加5条，黏聚力和内摩擦角分别降低57.09%和49.59%。

Study on water retention and strength properties of red clay containing cracks

Red clay slopes are easy to produce cracks under cyclic drying and wetting, and the development of cracks will adversely affect the hydraulic properties and strength of the soil, thus reducing the slope stability. With Changsha red clay as the research object, red clay specimens with different numbers of cracks were prepared, and then permeability tests, soil water retention tests, and direct shear tests were performed. The evolution of saturated permeability coefficient, soil water characteristic curve, and shear strength parameters of red clay with the crack number and dry density are revealed, and the corresponding mathematical expressions are established. The results show that the order of magnitude of the soil permeability coefficient is 10-5-10-7m·s-1. The saturated permeability coefficient drops with an increase in dry density and grows exponentially with an increase in crack number. When the crack number increases by 5, the saturated permeability coefficient increases by 66.4 times. The specimen with a lower dry density or a larger crack number has a higher saturated volumetric water content, the volumetric water content drops faster with the matric suction in the drying process; as a result, the residual water content is lower, and the water retention capacity is worse. The shear strength parameters of red clay are directly proportional to dry density and inversely proportional to crack number. Particularly, when the dry density increases by 0.28g·cm-3, the cohesion and internal friction angle increase by 2.35 times and 0.94 times, respectively; when the crack number increases by 5, the cohesion and internal friction angle decrease by 57.09% and 49.59%, respectively.