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利用Quanta环境扫描电子显微镜(ESEM)对延安某填方场地的压实黄土(Q_3和Q_2黄土混合)进行微观结构测试,得到最优含水量下不同干密度黄土微观结构图片。采用Image-Pro Plus图像处理软件对压实黄土孔隙微观结构进行了定量评价,并运用多元线性回归分析法建立了孔隙微观结构量化参数与压实黄土侧限压缩、直剪强度的关系。研究结果表明:随着干密度的增大,孔隙面积比、平均孔径、平均平面形状系数、平均分形维数逐渐减小,概率熵逐渐增大,孔隙分布越趋于均匀,整体力学性质越稳定;tanφ主要受孔隙的平面形状系数影响,黏聚力、压缩模量(E_(s0.05-0.1)、E_(s 0.1-0.2)、E_(s 0.2-0.4))和压缩系数主要与孔隙面积比有关,而E_(s 0.4-0.8)则与孔隙的概率熵密切相关。通过关联性分析,可知400 k Pa是孔隙面积比变化幅度明显减小时的特征压力值,而孔隙面积比变化直接关系沉降变形,400 k Pa也是压实黄土在最优含水量下沉降变形幅度明显减小时的特征压力值。
The microstructure of compacted loess (mixture of Q_3 and Q_2 loess) at a fill site in Yan’an was tested by Quanta Environmental Scanning Electron Microscope (ESEM) to get the pictures of microstructure of loess with different dry density under the optimal water content. The pore microstructure of compacted loess was quantitatively evaluated by using Image-Pro Plus image processing software. The relationship between the quantitative parameters of pore microstructure and the lateral compression and direct shear strength of compacted loess was established by multivariate linear regression analysis. The results show that with the increase of dry density, the pore area ratio, the average pore size, the average planar shape coefficient and the average fractal dimension gradually decrease, the probability entropy increases gradually, and the pore distribution tends to be uniform and the overall mechanical properties become more stable ; tanφ is mainly affected by the planar shape coefficient of the pores. The cohesion, compressive modulus (E0.05-0.1), E0 (0.1-0.2) and E0 (0.2-0.4) Area ratio, while E_ (s 0.4-0.8) is closely related to the probability entropy of pores. The correlation analysis shows that 400 kPa is the characteristic pressure value when the pore-area ratio decreases obviously, while the pore area ratio is directly related to the subsidence deformation. 400 kPa is also the obvious amplitude of settlement deformation of the compacted loess under the optimal water content Reduced characteristic pressure value.