多次冻融条件下土体的融沉性质研究

以青藏铁路那曲物流中心站场路基填料为研究对象,通过室内试验深入研究和分析了压实度、荷载以及冻融次数对土体融沉性质的影响规律。研究结果表明：第1次冻融过程中压实度大的试样的冻胀融沉量小,而经历多次冻融后压实度大的试样的冻胀融沉量则变大；多次冻融后较大压实度的试样表现为隆起变形,而较小压实度的试样则表现为压密变形,即不同压实度试样在经历多次冻融后压实度趋于某一定值；存在一临界压实度值,该值下多次冻融后试样高度不发生变化；荷载的压密作用在抑制冻胀变形的同时也加剧了试样的融沉变形,总体变形量随荷载的施加和增大而增大；补水条件下多次冻融后试样的含水率远远大于初始含水率,因此应做好防排水措施；外界水源补给量随冻融次数的增加而减小,并在经历3次冻融后达到稳定,且冻结过程中的补水量远远大于融化过程中的补水量；融沉系数随冻融次数的增加先增大而后减小并在经历5次冻融后趋于稳定,因此可将5次冻融后的融沉系数作为评价土体融沉性质的指标。

Thaw subsidence properties of soils under repeated freeze-thaw cycles

For the subgrade fillings of Naqu Logistics Center station along Qinghai-Tibet Railway, the influencing rules of compactness, load and freeze-thaw cycles on the thaw subsidence properties are deeply analyzed in laboratory tests. The results show that: compared with that of the 1^st freeze-thaw cycle, the frost heave and thaw subsidence deformation of the sample with higher compactness changes from small to large after several freeze-thaw cycles. The samples with higher compactness exhibit heave deformation, while those with lower compactness present compaction after repeated freeze-thaw cycles, namely, the samples with different compactnesses tend to a certain compactness. Meanwhile, there is a critical compactness, with which the height of the samples does not change after repeated freeze-thaw cycles. The compactness effect of load restrains the frost heave deformation and increases the thaw subsidence deformation, and the total deformation increases with the increasing increment of load. The moisture content of the samples is more greater than the initial moisture content after repeated freez-thaw cycles. The amount of water supply decreases with the increasing increment of freeze-thaw cycles and then becomes steady after 3 freeze-thaw cycles, and the amount of water supply in freezing process is larger than that in thawing process. The thaw subsidence ratio increases first and then decreases to be steady after 5 freeze-thaw cycles with the increasing increment of freeze-thaw cycles, and the thaw subsidence ratio of the 5^th freeze-thaw cycle is recommended for assessing the thaw subsidence of soils.