摘要
为探究压实黄土(Q_2)溶滤变形特性,开展12种应力组合条件下的宏观溶滤试验及不同浸水时长的微观电镜扫描试验。宏观试验结果表明,溶滤应变及强度参数变化具时效性;其中,溶滤轴、体应变及应变率近似自然指数变化,黏聚力随浸水时长增加而减小,内摩擦角变化不大。围压应力对溶滤变形有阻碍作用,湿化应力水平s对溶滤应变有促进作用,并决定其量级。微观参数定量分析表明,随浸水时长增加,微观孔隙的孔径、概率熵和分形维数减小,团粒概率熵和分形维数增大,团粒粒径和曲率系数变小,微观孔隙比和连接系数分别减小和增大。孔径与粒径均减小的现象表明,溶滤变形是浸水和压力共同作用下的压密过程。其次,试样粒径变化率随s减小趋于降低,表明微结构破坏重组程度与s成正比。此外,通过KPCA法确定了影响溶滤体应变的3个主要参数为孔径、孔隙分形维数和曲率系数;影响黏聚力的2个主要参数为孔隙概率熵和团粒分形维数。
In order to explore the leaching deformation characteristics of compacted loess(Q_2),macroscopic leaching tests with 12 kinds of stress combinations and SEM tests with different immersion times were carried out. The results indicate that the changes of leaching strain and strength parameters have timeliness characteristics. The leaching axis,bulk strain and strain rate vary with the immersion time in a natural exponential function. The cohesive force decreases with increasing the duration of immersion but the internal friction angle changes little. For test control variable,the confining pressure has a hindering effect on the leaching deformation,and the slaking stress promotes the process of the leaching strain and determines the magnitude of the leaching strain. The quantitative analysis of microscopic parameters shows that,with increasing the immersion time,the pore size,the probability entropy and the fractal dimension of micro pores decrease while the probability entropy and fractal dimension of the cluster increase,and that the microscopic void ratio,the cluster size and curvature coefficient of the cluster decrease as the immersion time increases but the connection coefficient increase. The decreases of the pore size and the particle size indicate that the leaching deformation is a compaction process under the combined action of the immersion and the pressure. The change rate of the cluster size decrease with decreasing the slaking stress,which indicates that the degree of microstructure failure and recombination is proportional to the slaking stress. Three main microscopic parameters affecting the leaching volumetric strain such as the pore size,the fractal dimension of pores and the microscopic curvature coefficient,and two parameters influencing the cohesion including the pore probability entropy and the cluster fractal dimension were determined by KPCA method.
引文
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