干湿循环条件下膨胀土的力学性质与开裂行为

Mechanical Properties and Cracking Behavior of Expansive Soil under Dry and Wet Cycling Conditions

针对南水北调中线工程中膨胀土存在的工程问题,取南阳膨胀土进行干湿循环处理,利用三轴压缩试验仪对土样进行力学测试,并观测干燥土样的裂缝发展特征,研究了不同干湿循环次数下膨胀土的力学特征和开裂行为。试验结果表明,膨胀土的应力—应变曲线均为应变硬化曲线,土体的粘聚力、内摩擦角随干湿循环次数增加而逐渐减小,且分别表现为指数型和线性衰减趋势;裂隙率随干湿循环次数增加保持指数型增加;裂隙率与膨胀土强度指标同步变化。由SEM扫描试验观测到干湿循环使得膨胀土颗粒间的微裂隙逐渐扩张,从而导致表面裂隙的改变和力学性能的衰减。研究成果对于渠道边坡的防护设计有重要意义。

In order to study the changes of microstructure and macroscopic mechanical characteristics of expansive soil with the development of drying-wetting cycles,triaxial compression tester was used to test the mechanics of the soil samples,and the crack development characteristics of the dry soil samples were observed.The results show that the stressstrain curves of expansive soil are all strain hardening curves,and the cohesion and internal friction angle of soil gradually decrease with the increase of dry and wet cycle times,and show exponential and linear attenuation trends,respectively.The fracture rate increases exponentially with the increase of dry and wet cycle times.The change of fracture rate is synchronous with that of strength index of expansive soil.It can be observed from the SEM scanning test that the microcracks between the expansive soil particles gradually expand due to the dry and wet cycle,which leads to the change of surface cracks and the attenuation of mechanical property.The research results have significance for protective design of channel slope.