粉砂土反复冻胀融沉特性试验研究

Experimental study of repeated frost heave and thaw settlement properties of silty sand

针对深季节冻土区的特殊环境,通过室内试验研究了粉砂土在不同初始含水率、干密度、荷载、冻融次数条件下的反复冻胀、融沉特性。研究结果表明:粉砂土的冻结温度为-1.03°C;其冻胀融沉变形随冻融次数的增加呈现波浪式起伏变化,并最终趋于稳定状态;经历多次冻融后,干密度较大试样整体表现为膨胀,干密度较小试样整体表现为压密;上部荷载在抑制冻胀的同时加大了试样的整体融沉变形,却降低了每次冻融的冻胀率和融沉系数;存在一个最优初始含水率,该含水率条件下,试样经历多次冻融后的高度不发生变化;由于外界水源的补给,冻融后试样内部含水率均大于初始含水率;干密度和顶端荷载的增大均有效地抑制了外界水源的补给;4次冻融循环后,粉砂土的冻胀率、融沉系数均逐渐趋于稳定。

According to the special environment in deep seasonal permafr0st regigionS, the repeated frost heave and thaw settlement properties of silty sand under different initial moisture contents, dry densities,s, overburden pressures, mad freeze-thaw cycles were extensively investigated by means of laboratory experiments. Testing results show that; the freezing temperature iS -1.03 ℃. The deformation of frost heave and thaw settlement presents waves of ups and downs and then levels off in freeze-thaw cycles. Samples with higher dry density present expansion, while samples with lower dry density present compaction after repeated freeze-thaw cycles. The overburden pressure restrains the amount of frost heave, while increasing the amount of thaw settlement. However, the overburden pressure reduces the frost heave ratio and thaw settlement coefficient in every freeze-thaw cycle. At the optimal value of initial water content, the height of sample does not change after repeated freeze-thaw cycles. Due to water supplying to the samples, the water contents of samples frozen and thawed in the open system are greater than the initial water content. The increases of dry density and overburden pressure effectively restrain the outside water supply. The frost heave ratio and thaw settlement coefficient in every freeze-thaw cycle levels off after 4 freeze-thaw cycles,