干湿循环作用下压实黄土湿陷特性试验研究

压实黄土作为重要的填筑材料,广泛应用于我国西北、华北公路、铁路、机场等基础设施建设中.由于降雨及蒸发的周期性变化,黄土路基及基础经历着强烈的干湿交替作用.基于此,开展压实黄土风干干燥-滴水增湿条件下的干湿循环试验,利用双线法测试最佳含水量条件下不同初始压实度的黄土土样干湿循环前后的湿陷系数.结果表明:没有经历干湿交替作用的土样,湿陷系数随着压实度的增大而快速减小,当压实度达到90%,提高压实度对于黄土湿陷变形特征的影响较小;5次干湿循环作用后,不同压实度下的试样的湿陷系数均明显增大,且压实度越大,干湿作用对其湿陷变形的影响越显著;压实度K=95%试样在经历5次干湿循环作用后土样上部出现肉眼可见的细微孔隙,体积膨胀,有可溶盐析出,湿陷系数达到0.017,土样出现二次湿陷.

Study on collapse characteristic of compacted loess subjected to cyclic drying and wetting

Collapsible loess are widely distributed in arid and semi-arid regions of North China. As an inexpen-sive filling material,it can serve as a kind of foundation soil and be used in some infrastructures such as the high-way,railway,airport,etc. However,cyclic drying and wetting usually occurs in loess subgrade/foundation due to periodic variation of rainfall and draught. A series of Oedometer tests are performed to measure the collapsibili-ty coefficients after cyclic drying and wetting and to study its influence on collapse characteristic of compacted loess. The test results show that the collapsibility coefficient rapidly decreases with the increase of degree of com-paction,but it changes very little when the degree of compaction is above 90%. Compared with the initial speci-mens,collapsibility coefficient of the specimens under five drying and wetting cycles are all increased to some degree,the variation in collapsibility coefficient increases with the increase in the initial degree of compaction. For the loess sample with a degree of compaction of 95%,after five drying and wetting cycles,the collapsibility coefficient exceeded 0. 015 at 200 kPa stress,which shows that the compacted loess sample exhibited the second-ary collapse.