石灰改良黄土渗透性与孔隙结构的关系研究

A Study of the Relationship Between Permeability and Pore Structure of Lime-treated Loess

土是一种具有多孔介质的岩土工程材料,其微观孔隙结构决定着宏观渗透性。为了研究渗透特性与孔隙结构之间的依存关系,以石灰改良黄土为研究对象,首先对不同石灰掺量下的改良黄土进行室内变水头渗透试验,随后选取有代表性土样进行扫描电镜(SEM)试验,并利用Image-Pro Plus 6.0(IPP)图像处理软件统计不同石灰掺量下改良黄土的微观孔隙结构参数,结合室内渗透试验结果建立宏观渗透特性与微观孔隙结构之间的联系。结果表明:随着石灰掺量的增加,充填于大中孔隙的结晶胶结物不断增多,对应微观图像中大中孔隙的数量、面积、面孔隙度及大孔的平均直径逐渐减小,而微小孔隙的数量、面积及孔隙的分形维数呈上升趋势,孔隙结构趋向复杂化,使得有效渗流通道占比减小,从而降低了土体渗透性,说明微观孔隙结构参数与宏观物理性质存在密切联系,在一定程度上可以反映宏观物理性质的变化。

Soil is a kind of geotechnical engineering material with porous media,and the microscopic pore structure determines macroscopic permeability.To investigate the responsibility between permeability characteristics and pore structure,the falling-head permeability tests at various lime contents are carried on lime-treated loess firstly,and then the Scanning Electron Microscope(SEM)is conducted on some typical specimens which use the Image Pro Plus 6.0(IPP)Image processing software to count the microscopic pore structure parameters of the improved loess at various lime contents,and,by combining the results of the laboratory permeability test,establish the connection between the macroscopic permeability characteristics and the microscopic pore structure.The results show that with the increase of the lime contents,the crystalline cement filling the large and medium pores is increasing,corresponding to the number,area,surface porosity of the large and medium pores and average diameter of the large pores in the microscopic image are gradually reduced,but the number and area of small and micro pores and the fractal dimension of pores are on the rise,and the pore structure tends to be complicated,which reduces the proportion of effective seepage channels.Therefore the permeability of the soil is reducing.It is indicated that microscopic pore structure parameters are closely related to macroscopic physical properties,which can reflect changes in macroscopic physical properties to a certain extent.