As a completed decomposed product of granite rock, the granite residual soil widely distributes in South China with a special soil structure that can be easily damaged under external disturbance. Therefore, studying the evolution of soil cracks during the loading process is important for engineering practice that needs to evaluate the soil shear strength, such as slope stability analysis. The purpose of this study is to investigate the micro-structure for the intact granite residual soil under external loading base on X-ray computed tomography (CT) through global and local scanning (with resolutions of 180 µm and 26.7 µm, respectively). The micro-structural evolution of the cross-sections of soil column extracted from a granite residual soil layer under axial loading was investigated by CT scanning with a 0.5 mm slice thickness. The number of cracks (including macro-cracks and meso-cracks), area ratios and porosity corresponding to varying loading stages (initial, peak-stress and failure) were analyzed based on the cross-sectional CT images. Test results shows that the structure strength of the soil was mainly subject to macro-cracks. In addition, the increase of the porosity is mainly attributed to the generation and expansion of the cracks along sandy particle under external loading. This study can provide theoretical support and data support for understanding the micro-structural evolution of granite residual soil that is commonly encountered in civil engineering.

作为花岗岩岩石的一个完整的分解产物，花岗岩残余土壤在华南地区分布广泛，具有特殊的土壤结构，在外部干扰下很容易被破坏。因此，研究加载过程中土壤裂缝的演变对需要评估土壤抗剪强度的工程实践（例如边坡稳定性分析）具有重要意义。本研究的目的是通过X射线计算机断层扫描（CT）通过整体和局部扫描（分辨率分别为180 µm和26.7 µm）来研究外部载荷下完整的花岗岩残余土壤的微观结构。通过CT扫描以0.5mm的板厚研究了花岗岩残余土层在轴向荷载作用下土柱断面的微观结构演变。根据横截面CT图像分析了与变化的加载阶段（初始，峰值应力和破坏）相对应的裂纹数量（包括宏观裂纹和细裂纹），面积比和孔隙率。试验结果表明，土壤的结构强度主要受到宏观裂纹的影响。另外，孔隙度的增加主要归因于外部载荷下沿着沙粒的裂纹的产生和扩展。该研究可以为理解土木工程中常见的花岗岩残积土的微观结构演化提供理论支持和数据支持。试验结果表明，土壤的结构强度主要受到宏观裂纹的影响。另外，孔隙度的增加主要归因于外部载荷下沿着沙粒的裂纹的产生和扩展。该研究可以为理解土木工程中常见的花岗岩残积土的微观结构演化提供理论支持和数据支持。试验结果表明，土壤的结构强度主要受到宏观裂纹的影响。另外，孔隙度的增加主要归因于外部载荷下沿着沙粒的裂纹的产生和扩展。该研究可以为理解土木工程中常见的花岗岩残积土的微观结构演化提供理论支持和数据支持。