干湿循环作用下伊犁黄土的强度及微观特性

为探讨干湿循环作用下伊犁黄土的强度劣化规律和微观结构特性,进行了五种干湿循环路径下的三轴剪切试验及扫描电镜测试,分析了不同干密度、干湿循环幅度和次数对伊犁黄土抗剪强度的影响和微观孔隙分布的演化规律,并进行了宏观强度和微观孔隙损失机制之间的探讨。结果表明:干湿循环幅度越大、循环次数越多,伊犁黄土抗剪强度的衰减速度越快,衰减幅度越大,原状土在5次干湿循环后的三轴剪切强度接近重塑黄土；同种干密度的伊犁黄土的黏聚力随循环次数的增加而降低,同一干湿循环路径下干密度为1.55g/cm3时,伊犁黄土的黏聚力劣化最显著,而干湿循环对内摩擦角有轻微影响。另外黏聚力的劣化与孔隙面积比和孔隙特征参数的变化有关,干湿循环后孔隙面积比和孔隙特征参数增加率越大,黏聚力劣化越明显；内摩擦角的变化与孔隙分形维数的变化趋势相近,但变化不显著。

Study on the Strength and Microscopic Characteristics of Ili Loess under the Action of Wetting-Drying Cycles

To investigate the strength degradation and microstructure characteristics of Ili loess under wetting-drying cycling, triaxial shear tests and scanning electron microscopy tests were conducted under five wetting-drying cycling paths. The effects of different dry densities, wetting-drying cycling amplitudes, and cycles on the shear strength of Ili loess and the evolution of micro pore distribution were analyzed. The relationship between macro strength and micro pore loss mechanisms was also explored. The results show that the greater the wetting-drying cycle amplitude and the number of cycles, the faster the attenuation rate of the shear strength of Yili loess, the greater the attenuation amplitude, and the triaxial Shear strength of undisturbed soil after five wetting-drying cycles is close to remolded loess; The cohesive force of Ili loess with the same dry density decreases with the increase of cycles. When the dry density is 1.55g/cm3 under the same wetting-drying cycle path, the cohesive force of Ili loess deteriorates most significantly, while the effect of dry wet cycles on internal friction angle is slightly significant. In addition, the deterioration of cohesion is related to changes in pore area ratio and pore characteristic parameters. The greater the increase rate of pore area ratio and pore characteristic parameters after wetting-drying cycling, the more obvious the degradation of cohesion; The change trend of internal friction angle is similar to that of pore Fractal dimension, but the change is not significant.