干湿循环下复合黄土裂隙演化与力学特性试验

Experimental Study on Crack Evolution and Mechanical Properties of Composite Loess Under Dry-wet Cycles

为分析干湿循环作用下复合黄土裂隙演化与力学特性,针对含香根草根系的加筋黄土,系统开展干湿循环效应下的直剪试验,并采用PCAS图像处理技术量化细观结构特征参数。研究结果表明,裂隙发育具有记忆性,随着干湿循环次数的增加,裂隙各特征参数逐渐增大并趋于稳定,且在黄土中加入植物根系能有效抑制土体裂隙发育;土体抗剪强度随干湿循环次数增加呈减小趋势;干湿循环作用下土体抗剪强度随根系含量增加呈指数型增大特征;根—土复合体粘聚力随干湿次数的增加骤减,经过5次干湿循环后,粘聚力较初始值损失最高达48.78%,而内摩擦角并无明显变化;通过灰色关联法分析发现裂隙面积率与粘聚力衰减率的关联性最强,其与粘聚力的关联度为0.817~0.888,相应权重为0.413~0.424;构建的干湿循环效应下粘聚力预测模型可较好定量化预测根—土复合体粘聚力变化规律。

To analyze the crack evolution and mechanical properties of composite loess under dry-wet cycles, the direct shear test under the effect of drying and wetting cycles was systematically carried out on the reinforced loess containing vetiver roots. The PCAS image processing technology was used to quantify the characteristic parameters of the mesoscopic structure. The research results show that the development of fissures is obvious. With the increase of the number of dry and wet cycles, the characteristic parameters of the fissures gradually increase and become stable, and adding plant roots to the loess can effectively inhibit the development of soil fissures. The shear strength of the soil decreases with the increase in the number of dry-wet cycles. The shear strength of the soil under the dry-wet cycles increases exponentially with the increase of the root content. The root-soil composite cohesion decreased sharply with increase of the number times of the dry-wet. After 5 times of dry-wet alternation, the cohesive force lost up to 48.78% compared with the initial value, while the internal friction angle did not change significantly. The crack area ratio and cohesive force were found through gray correlation analysis. The attenuation rate has the strongest correlation, and its correlation with cohesion is 0.817-0.888, and the corresponding weight is 0.413-0.424. The cohesion prediction model based on the dry-wet cycle effect can better quantitatively predict the change law of root-soil cohesion.