初始含水量及冻融循环对黄土微结构的影响

冻融循环作用是季节性冻土地区工程病害发生的主要致灾因子。在冻融循环作用下,土体结构性逐渐丧失、强度不断劣化,最终导致灾害的发生。以延安市延安新区黄土为研究对象,配置不同初始含水量试样,经历0、1、3、6、10、15次冻融循环,通过SIGMA500扫描电子显微镜观察试样微观结构的演化规律。试验结果表明:随着冻融循环次数的增加,试样内部裂纹、裂缝不断发育演化,水分迁移通道不断扩展;初始含水量高的试样裂纹裂缝发育演化越明显;冻融循环作用使得试样内部大颗粒分解为若干小颗粒、颗粒表面的棱角不断磨圆、表面起伏不断减小;当冻融循环10次以后,颗粒大小、颗粒形状、表面起伏趋于稳定,试样颗粒尺寸趋于统一,试样大孔隙减小,小空隙增多,总体孔隙率增大。试样颗粒间的胶结强度随着冻融循环次数的增加不断减小,破碎作用产生的小颗粒造成粒间的接触点增多,致使试样的内摩擦角增大。

Influence of initial water content and freeze-thaw cycles on Microstructure of Loess

Freezing thawing cycles are the main hazard factors of Engineering diseases in seasonally frozen soil area. Under the action of freeze-thaw cycles, the soil structure gradually loses and the strength deteriorates, which eventually leads to the occurrence of disasters.This paper takes Yanan city Yanan District of loess as the research object, the configuration of different initial water content of 0, 1, 3 sample experience, 6, 10, 15 times of freeze-thaw cycle, by SIGMA500 scanning electron microscope. The evolution of the microstructure of specimen,The test results show that with the increase of freeze-thaw cycles, the development of internal crack fracture evolution, moisture migration channel expansion; crack crack initial specimen with high water content development is more obvious; the effect of freeze-thaw cycles of the specimen within the particle is decomposed into small particles, if dry surface particles continuously rounded and angular surface fluctuation decreases, when the freeze-thaw cycle after 10 times of particle size, particle shape, surface stabilized, sample particle size tends to be uniform, the sample porosity decrease, small gap increased, total porosity increased; sample particles bond strength with the increase of freeze-thaw cycles decreases, the small particle crushing effect the point of contact between the particles caused by increased, resulting in samples of the internal friction angle increases.