中文摘要：

通过对西安Q_3原状黄土在冻融作用下的电镜扫描和三轴渗透试验,研究了原状黄土冻融过程渗透特性变化机理及规律。试验表明：冻融过程中由于土体内部冰晶生长及冷生结构形成导致原状黄土微观结构发生显著变化,融化后的黄土在一定程度上增大了渗透性;基于图像处理软件,计算得到孔隙面积比随冻融次数增加呈指数增加趋势,反映出冻融作用一定程度上破坏原状黄土结构强度,使土体渗透性增强,但多次冻融后结构强度和渗透特性趋于稳定。冻融过程试样表面产生不规则裂缝,且含水率越高,土体表面特征破坏越严重,是渗透性增强的主要原因。渗透系数随围压增大呈指数下降趋势,且高围压时渗透系数差异较小;渗透系数随初始含水率增加近似呈抛物线变化规律,但高围压下渗透系数与初始含水率抛物线变化规律不明显;渗透系数随冻融次数增加近似呈指数增加趋势,但低含水率试样渗透系数变化幅度较小。基于试验数据规律性,进一步得到了考虑围压、初始含水率及冻融次数影响的西安Q_3原状黄土渗透系数多变量预测模型。

英文摘要：

Based on the electron microscope scanning and triaxial permeability test of Q3 undisturbed loessfrom Xi＇an, the permeability of undisturbed loess during the freeze-thaw process was studied. Experimentresults show that during the freeze-thaw process,the growth of ice crystal and formation of cryogenic struc-ture result in obvious change of microstructure about undisturbed loess,and the permeability of loess is en-hanced. Using the image processing software,it is concluded that the void area ratio exponentially increas-es with the increase of freezing-thawing cycle number,representing that the structural strength of loess canbe destroyed by freezing-thawing. However,the strength and permeability of loess tend to be stable after re-peated freezing and thawing. Freezing-thawing makes the irregular cracks produced on the surface of thesample, and has a bigger influence with the increase of water content, which is the main reason for theenhancement of permeability. The permeability coefficient decreases exponentially with the increase of confin-ing pressure,and the permeability coefficient difference under high confining pressure is small. The permea-bility coefficient approximately follows the parabola rule with the increase of moisture content,and the ruleis not obvious under high confining pressure. The permeability coefficient exponentially increases with the in-crement of freezing-thawing number, and the permeability coefficient of sample with low water content hasa small change. Based on the regularity of test data,a multivariate prediction model was developed by con-sidering the influence of moisture content,freezing-thawing number and confining pressure.