固结条件下黏性土微观孔隙结构试验研究

Experimental study of microscopic pore structure of clay soil under consolidation consolidation

土体微观结构状态是控制土体稳定的重要因素,工程土体在宏观上表现出的复杂特性根本上取决于微结构的复杂性和不确定性。本文以德州市沉降区钻孔中黏性土层为研究对象,基于对电镜扫描图像的分析处理,从微观角度对不同深度黏性土的孔隙结构演化机制进行研究,并探讨土体初始结构状态对压缩性的制约关系。微观试验分析表明:固结荷载改变土体微结构类型,随着固结荷载增加,结构单元体由松散状态转变为团聚状态,土体密实度提高,孔隙面积减小。定量分析表明:固结压力将改变土体微结构要素,随着固结荷载增加,平均孔径减小、微小孔隙所占比例增加、孔隙形状不断调整最终趋于圆滑、集团化程度变高、土体定向性增强。上述试验为深入理解土体微观结构非线性问题.以及微观结构与宏观工程特性的相互作用机制提供了依据。

The microstructure state of soil is an important factor to control the stability of soil. The complex macroscopic characteristics of engineering soil are fundamentally determined by its complexity and uncertainty of microstructure. In this paper, taking the clay soil from the settlement area of Dezhou City as research object, based on the analysis and processing of scanning electron microscope images, the mechanism of pore structure evolution of clay soil taken from different depths was studied from the microscopic point of view. The constraint relation between the initial structure state and compressibility of soil was also discussed. Experimental results show that the consolidation load has changed the microstructure type of soil;with the increase of consolidation load, the structural units are converted from loose state to reunion state;the compactness of soil increases and the pore area decreases. Quantitative analysis shows that the consolidation pressure will change the micro-structural elements of soil. With the increase of consolidation load, the average pore size decreases and the proportion of micro-pores increases. The pore shape will eventually adjust to be smooth, and the degree of collectivization will increase, soil orientation enhanced. The above experiment provides an important basis for the further understanding of the nonlinear problem of soil microstructure and the interaction mechanism between microstructure and macroscopic engineering characteristics.