冻融过程对膨胀土裂隙演化特征的影响

干湿与冻融耦合作用是构成高寒地区恶劣气候条件的基本形式之一，对高寒区膨胀土输水渠道的正常运行产生严重影响。以北疆供水工程渠道现场渠基膨胀土为研究对象，开展了单向湿干及湿干冻融耦合循环作用下的裂隙试验，探讨了冻融过程对膨胀土裂隙演化规律的影响。通过对不同试验条件下的膨胀土试样进行CT扫描及三维重构，获得了不同循环次数作用下膨胀土内部裂隙的演化特征。试验结果表明：湿干及湿干冻融耦合循环作用下试样内部裂隙均呈现出由表层向内部的发展规律，裂隙的区域性分布明显。对比不同试验条件下试样内部裂隙的演化特征可知，湿干冻融耦合循环中的冻融过程对试样裂隙的开展深度影响显著，冻融过程造成试样内部裂隙的破碎断裂，宏观表现为非水平向长裂隙向短裂隙的转化。此外，研究还发现采用裂隙体积分数能较好地评价膨胀土试样经受不同循环次数作用下的裂隙发育规律。

Influences of freeze-thaw process on evolution characteristics of fissures in expensive soils

The coupling action of wetting-drying and freeze-thaw is one of the basic forms for the severe climate conditions in high and cold regions, which has significant influences on the normal operation of water supply canals in expansive soils in these regions. Based on the field expansive soils of water supply canals in the northern area of Xinjiang Uygur Autonomous Region, the fissures tests under the unidirectional wetting-drying and the cyclic action of coupling wetting-drying and freeze-thaw are conducted respectively to investigate the influences of freeze-thaw process on evolution rules of fissures in expansive soils. The evolution characteristics of the internal fissures in expansive soils with various cycles can be obtained through the CT scanning and 3D reconstruction. The test results show that the internal fissures in the samples under the two conditions both develop from the surface towards the internal part and the regional distribution of fissures can be obviously captured. A comparison of the evolution characteristics of the internal fissures under different test conditions indicates that the freeze-thaw process in the coupling cycle of wetting-drying and freeze-thaw has significant influences on the focal depth of the fissures, and the induced fracture is macroscopically characterized by the transformation from non-horizontal long fissures into short ones. In addition, it is found that the development of fissures in expansive soil samples under the action of various cycles can be successfully evaluated by using the volume fraction of the fissures.