不同初始湿密状态对黄土渗透特性影响规律研究OA

Loess is a special soil type widely distributed in the northwest of China,and it affects engi-neering stability and the efficient utilization of agricultural water resources due to its seepage characteris-tics.Yet,its seepage mechanism and dynamic seepage law under the coupling effect of water content and initial compaction(i.e.,complex moisture-density state)remain unclear.Taking Yangling loess as the research object,we conducted a series of unsaturated seepage tests with a permeameter(TST-55),and analyzed the evolution of water outflow time,variations of seepage coefficient and hydraulic gradient effect under different initial moisture-density states.The results show that the water outflow time of unsaturat-ed specimens is significantly prolonged with the increase of compaction degree.Under the condition of high compaction degree,the water outflow time shows an accelerated growth trend with the increase of in-itial water content;while the specimens with low compaction degree are insensitive to the changes of ini-tial water content.The seepage coefficients of all specimens stabilize with the seepage time,among which the seepage coefficient of high-compaction specimens is significantly negatively correlated with the initial water content;whereas that of low-compaction specimens shows no obvious regularity.The specimens are still in an incompletely saturated state under the steady seepage condition,and their steady seepage coef-ficient is always lower than the saturated value,with the correlation between saturated seepage coefficient and initial water content being much higher than that between unsaturated steady seepage coefficient and initial water content.The seepage coefficient is positively correlated with the hydraulic gradient,but the order of magnitude of the seepage coefficient remains unchanged.The seepage curve of low-compaction specimens presents a typical three-segment linear characteristic,which gradually weakens and transforms into a two-segment linear characteristic with the increase of compaction degree.The compaction degree mainly affects the trend of segmentⅠandⅢof the curve,while the initial water content dominates the e-volution of segmentⅡ.The research results reveal the dynamic law of unsaturated seepage of loess under the coupling of moisture and density.The findings not only deepen the understanding of the synergistic mechanism of multiple factors,but also provide a theoretical support and quantitative basis for engineer-ing seepage control,soil and water conservation,as well as ecological restoration in loess areas.