冬灌区黄土湿陷性的反复冻融效应

Effects of Repeated Freezing and Thawing on Collapsibility of Loess in Winter Irrigation Zone

为了探索冻融循环对冬灌区黄土湿陷性的作用规律,结合宁夏气候和黄土区域性特点,应用封闭单向冻融法,试验研究了冬灌区黄土湿陷性的反复冻融效应。试验结果表明:冻融使黄土的湿陷性增大,冻融引起的湿陷系数增量随冻融循环次数的增加而增大,在冻融循环12次后基本达到稳定,二者间存在相关性很好的双曲线关系。在含水率为定值14.0%时,黄土湿陷系数的冻融效应随干密度的增大逐渐增大;在干密度为定值1.45 g/cm^3时,黄土湿陷系数的冻融效应随含水率的增大呈先增大后减小的趋势,最不利含水率约为22.0%。湿陷系数的冻融效应存在最不利含水率,黄土工程应尽量避免在最不利含水率下受冻,尤其是密实度大的压实黄土。

In order to explore the effect of freezing and thawing on collapsibility of loess in winter irrigation zone, combined with the local characteristics of climate and loess, the effect of repeated freezing and thawing on collapsibility of loess in winter irrigation zone were experimentally studied by using one-dimensional closed unilater-al freezing and thawing method. Results show that the freezing and thawing make the collapsibility of loess in-crease. With the increase of the freeze-thaw cycles, the increment of collapsible coefficient caused by freeze-thaw increases first and remains at a stable level after 12 times. The increment of collapsible coefficient fitted fairly well with freeze-thaw cycles in a hyperbola function. As water content is fixed at 14. 0% , the effect of freezing and tha-wing on coefficient of collapsibility increases with the increase of dry density. As dry density is fixed at 1. 45 g/ cm3, the effect of freezing and thawing on coefficient of collapsibility first increases, and then decreases with the in-crease of water content. The worst water content is about 22. 0%. The effect of freezing and thawing on coefficient of collapsibility has one of worst water content, and loess engineering should avoid suffering cold under the worst water content, especially the compacted loess.