膨胀土干湿循环胀缩裂隙的定量分析

为研究膨胀土在降雨与蒸发过程中的胀缩裂隙演化规律，对原状膨胀土进行干湿循环的CT扫描试验。利用Matlab软件编写程序对土体CT图进行三维体重建以及裂隙信息的提取，从定性与定量的维度研究土体三维空间裂隙与干湿循环之间的关系。定性研究发现，裂隙发育开始于土体内部初始孔洞与微纹裂等薄弱处，并扩展延伸，形成裂隙面、裂隙体，最后形成复杂的三维裂隙网络；随着干湿循环的进行，裂隙面积和体积逐渐增加，最后趋于稳定。定量研究发现，裂隙面积沿试样轴向的分布具有明显的周期性规律，随着干湿循环的进行，周期逐渐减小，振幅A先增加后减小；裂隙开展分为3个阶段，即裂隙酝酿期、裂隙快速发育期和裂隙平稳发展期，而裂隙发育主要发生在裂隙快速发育期。得出了试样径向裂隙面积、轴向高度与累计干缩体变之间的近似关系，以裂隙体积定义了符合Logistic函数变化规律的扰动函数，可以预测裂隙在试样局部的发展及分布情况，为裂隙膨胀土的渗透特性以及整体与局部的应力、应变研究提供参考。

Quantitative analysis of swelling and shrinkage cracks in expansive soil

To study swell-shrink fissure evolution rule of expansive soil in the natural rainfall and evaporation process, wetting-drying cycles tests, and CT scanning tests have been done. The three-dimensional reconstruction of soil CT images and the extraction of fracture information are carried out using Matlab software. The relationship between three-dimensional space cracks and wetting and drying cycles is studied from qualitative and quantitative dimensions. The relationship between soil’s fracture in three dimensional space and d wetting-drying cycles are studied from the qualitative and quantitative dimensions. Qualitative studies have found that the development of fractures begins at the weak spots such as initial pores and microcracks within the soil; and thus extends to form fracture surfaces and fissure bodies; and finally forms a complex three-dimensional fracture network. As the wetting-drying cycles progresses, the area and volume of the fracture gradually increase; and finally tend to stability. Quantitative studies have found that the distribution of fracture area along the axial direction of the sample has obvious periodicity. As the wetting-drying cycle proceeds, the period gradually decreases, and the amplitude A increases first and then decreases. The development of fissure is divided into three stages: i.e, fissure gestation period, fissure rapid development period and fissure steady development period; and fissure development mainly occurs during fissure development period. The approximate relationship between radial fracture area, axial height, and cumulative dry shrinkage volume change is obtained. The fracture volume is defined as a function of the Logistic function. It can predict the development and distribution of fissures in the sample, and can provide references for the permeability characteristics of fissured expansive soil and the study of the overall and local stress and strain.