影响黏性土表面干缩裂缝结构形态的因素及定量分析

Factors affecting the surface cracking in clay due to drying shrinkage

本文在室内试验的基础上,采用计算机图片处理技术,在对不同黏土厚度、干湿循环次数和土质成分等条件下黏性土干缩裂缝网络进行对比和定量分析的基础上,探讨了聚丙烯纤维对黏性土干缩裂缝的抑制作用和机理。结果表明,土层厚度、干湿循环次数和土质成分对裂缝网络的节点个数、裂缝条数、裂缝长度和宽度、块区个数、块区面积、裂缝率和裂缝网络的分形维数等定量参数均有一定的影响;裂缝网络的节点个数、块区个数和裂缝率是描述其形态结构和几何特征的基本指标;在黏性土中加入适量的聚丙烯纤维能够改变干缩裂缝的发展规律,降低土体的裂隙率,提高土体结构物的稳定性和防渗性能。

The computer image processing technique was applied to quantitatively analyze and describe the structure and geometric characteristics of cracks in clay due to drying shrinkage. The factors influencing the shrinkage such as thickness of soil sample, wetting-drying cycle and composition of soil were taken into account. The restraining effect of polypropylene fiber on the shrinkage cracks of clay and its mechanism are also investigated. It is found that the intersections, length, width and numbers of cracks, numbers of aggregates, aggregate area, porosities （crack area in percentage of the image） and fractal dimensions of crack networks are significantly affected by the thickness of soil sample, wetting-drying cycle and soil composition. The crack segments, numbers of aggregates and porosities should be considered as key parameters in analyzing the structure and geometrical characteristics of crack pattern. The polypropylene fibers can inhibit the expansion of cracks and improve the stability of soil structure as well as the impermeability of soil.