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中文摘要：
通过补水条件下的冻融循环试验,对经历不同冻融次数的压实黄土土样进行电镜扫描图像的定量分析,同时进行土样宏观物理性质的测试,探讨微观结构与宏观性质之间的关系,揭示冻融循环对压实黄土结构影响的过程与机理。研究结果表明,随着冻融循环次数的增加,土样内部冰晶的生长及冷生结构的形成导致土样中孔隙体积增加,土颗粒受到挤压并形成新的土骨架结构。大中孔隙个数及其所占孔隙总面积百分比显著增加,由2次冻融循环后的78%增加至31次冻融循环后的90%。同时,土样中出现一些由大中孔隙组成的、对黄土湿陷性起控制作用的架空孔隙。宏观物理性质测试表明,随着冻融循环次数的增加,土样含水率显著增加并出现重分布,而干密度则先减小而后基本保持不变。31次冻融循环后,土样上下层含水率相比于初始值增加分别超过140%,50%,而干密度则由初始的1.86 g/cm3减小为1.55 g/cm3,减幅为17%。微观结构和宏观性质的改变均表明了冻融作用对于压实黄土结构的弱化作用。
英文摘要：
After a series of laboratory experiments in an open system,the impacts of freeze-thaw cycles on the structure of compacted loess are studied by means of the quantitative analysis of scanning electron microscope images.The physical properties of the soils are tested simultaneously to discuss the relationship between microstructure and macro-properties of the loess.The results of microstructure analysis show that,with the increase of freeze-thaw cycles,the formation of cryogenesis results in obvious enlargement of pore volumes and therefore extrusion and redistribution of soil particles.The ratio of big-and mid-pore area to the total pore area increases from 78% after 2 cycles to 90% after 31 cycles.Meanwhile,some pores with open structure,which controls the loess collapsibility,are formed during the cycles.The results of macro-properties test show that,during the cycles,the water content of the samples increases significantly and is redistributed,and the dry density of the samples decreases initially and then keeps almost constant.After 31 cycles,the water contents at the upper and lower parts of the sample increase by more than 140% and 55%,respectively,whereas the dry density of the sample decreases from the initial value of 1.86 g/cm3 to 1.55 g/cm3,about a depression of 17%.Collectively,the results from both the micro-and macro-analyses indicate that the freeze-thaw action significantly weakens the structure of compacted loess.
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