冬灌区黄土压缩性的反复冻融效应

Effects of repeated freezing-thawing on compressibility of loess in winter irrigation area

结合宁夏气候和黄土的区域性特点,应用封闭系统一维单向冻融试验方法,研究了冬灌区黄土压缩性的冻融效应,分析了压缩性的冻融效应与冻融变形的相关性。结果表明:冻融引起的压缩系数增量随冻融循环次数的增加而增大,在12次冻融循环前变化剧烈,一定冻融循环后趋于稳定。压缩系数增量达到稳定的冻融循环次数与含水率和初始干密度有关,冻融循环使密实度和含水率对压缩性的冻融效应增大。含水率为定值14.0%时,压缩性的冻融效应随初始干密度的增大而增大。初始干密度为定值1.45 g/cm3时,压缩性的冻融效应随含水率的增大而提高。压缩系数增量与冻融变形率间存在良好的线性相关性,可用二者间的相关性模型预测宁夏黄土压缩性的冻融效应。

Combined with the local characteristics of climate and loess , the effect of freezing-thawing on the compressibility of loess in winter irrigation zone was experimentally studied by using the unilateral freezing and thawing method in a closed system. Correlation between the compressive freezing-thawing effect and the freezing-thawing deformation was analyzed. Results show th a t, with the increase of the freezing-thawing cycles , the increment of compression coefficient caused by freezing-thawing increases dramatically before 12 cycles and tends to be stable after a certain number of cycles. And the number of cycles for the increment of compression coefficient to stabilize is related to the initial dry density and water content. The repeated freezing-thawing makes the effect of compactness and water content on the effect of freezing-thawing on the compressibility increase. As the water content is fixed at 14. 0% , the effect of freezing-thawing on the compressibility increases with the increase of initial dry density. As the initial dry density is fixed at 1. 45 g cm3, the effect of freezing-thawing on the compressibility increases with the increase of water content. There is a perfect linear correlation between the increment of compression coefficient and the freezing-thawing deformation rate, which can be used to predict the effect of freezing-thawing on the compressibility of loess in Ningxia.