干湿循环下非饱和粉质黏土抗剪强度特性试验研究

Experimental Study on Shear Strength Characteristics of Unsaturated Silty Clay under Wetting-Drying Cycles

摘要: 土的抗剪强度是土力学基本问题，路基路床区土体干湿循环导致性质劣化，影响稳定性和耐久性，易引发路基灾害，该问题受到广泛关注。基于此，本研究针对路基路床区土体，开展了针对不同干湿循环频次的非饱和三轴剪切实验，旨在探讨循环次数变化对抗剪强度指标的影响规律，并阐明干湿循环作用对粉质黏土路基强度衰减特性的影响机理。结果表明：在干湿循环下，粉质黏土展现出了应变软化特性的应力–应变响应，试件呈现剪切滑裂面；随着循环次数的递增，峰值应力呈现出递减趋势，具体而言，在经历了三次循环后，35 kPa、50 kPa和100 kPa净围压条件下，其峰值应力分别衰减了26.4%、13.0%和18.2%。此外，总粘聚力亦随循环次数的增加而逐渐降低，三次循环后降低了26.6%，而有效内摩擦角变化无规律，仅下降了4.0%，劣化程度远小于总粘聚力。

Abstract: The shear strength of soil is a basic problem of soil mechanics. The dry-wet cycle of soil in subgrade bed areas leads to deterioration of properties, affects stability and durability, and is easy to cause subgrade disasters. This problem has received extensive attention. Based on this, this study carried out unsaturated triaxial shear tests with different wetting-drying cycles for the soil in the subgrade bed area, aiming to explore the influence of the number of cycles on the shear strength index and to clarify the influence mechanism of wetting-drying cycles on the strength attenuation characteristics of silty clay subgrade. The results show that under the dry-wet cycle, the silty clay exhibits the stress-strain response of strain-softening characteristics, and the specimen exhibits a shear slip surface. As the number of cycles increases, the peak stress shows a decreasing trend. Specifically, after three cycles, the peak stress decreases by 26.4%, 13.0% and 18.2% under the net confining pressure of 35 kPa, 50 kPa and 100 kPa, respectively. In addition, the total cohesion also gradually decreased with the increase of the number of cycles, which decreased by 26.6% after three cycles, while the effective internal friction angle changed irregularly, only decreased by 4.0%, and the degree of deterioration was far less than the total cohesion.