干湿循环作用下压实黄土三轴剪切特性试验研究

为研究干湿循环引起的压实黄土结构损伤对其应力-应变特征及三轴剪切强度的影响,对最优含水率条件下压实到干密度为1.7 g/cm~3的黄土试样进行不同路径的干湿循环试验和三轴剪切试验。结果表明:干湿循环对压实黄土的三轴剪切特性影响显著,随着干湿循环次数的增加,压实黄土的应力-应变曲线先急剧下移,再逐渐上移,最后趋于稳定;干湿循环对压实黄土三轴剪切强度具有劣化作用,存在临界干湿循环次数n_c,当干湿循环次数小于临界干湿循环次数时强度指标急剧减小,等于临界干湿循环次数时强度指标最小,大于临界干湿循环次数时强度指标逐渐增大并趋于稳定;分段函数能够较好反映三轴剪切强度指标的劣化规律和劣化过程;受干湿循环幅度影响,压实黄土存在干湿循环最劣含水率w_w,可以根据压实完成后黄土的瞬时含水率是否接近或等于最劣含水率来评价干湿循环对三轴剪切强度的劣化程度。

Experimental study on triaxial shear characteristics of compacted loess under drying and wetting cycles

A series of drying and wetting cycles test and triaxial shear test were carried out for the loess samples which were compacted to dry density of 1.7g/cm³ under the optimum moisture content condition to investigate the influence of the structure damage of the compacted loess caused by the drying and wetting cycles on its stress-strain characteristics and triaxial shear strength. The results indicate that the drying and wetting cycles have a significant effect on the triaxial shear properties of compacted loess,with the number of drying and wetting cycles increasing, the stress-strain curve of compacted loess moves down sharply, then up gradually, and finally tends to be stable. The drying and wetting cycles degrade the triaxial shear strength of compacted loess. The defined strength index degradation degree can better reflect the degradation rule and process of the triaxial shear strength index. Affected by the range of dry and wet cycles, there is the worst moisture content of drying and wetting cycles in compacted loess. The degradation degree of strength index is the largest under the condition of the worst moisture content. The degradation degree of triaxial shear strength can be evaluated according to whether the instantaneous moisture content of loess after compaction is close to or equal to the worst moisture content.