花岗岩残积土系花岗岩全风化产物，其内部组构非常特殊，表现为在外部荷载或浸水入渗环境下，强度明显弱化且极易发生软化变形，进而造成地面塌陷、边坡失稳等工程灾害。针对上述问题，本项目拟采用X-ray CT扫描设备及土工试验装置，对花岗岩残积土展开多尺度测试研究，具体如下：从细、微观角度揭示花岗岩残积土结构特征并建立与宏观物性指标的关联；展开花岗岩残积土在荷载、浸水条件下的力学试验测试和实时CT扫描，获取花岗岩残积土内部结构的动态演化过程，并从宏-细-微观角度对裂纹发育、扩展、贯通形态进行特征分类和量化研究，明确微细观结构损伤因子中对宏观力学影响的主控因素；引入表征土体结构变化特征的因子，建立花岗岩残积土损伤本构模型。该项目研究成果可以从细、微结构演化的角度揭示残积土强度弱化和遇水软化的内在机理，为解决花岗岩残积土相关的工程难题提供理论依据与方法支持。

As a completely weathered product of granite rock, completely decomposed granite soil (CDG soil) often represents a complex internal structure. It is characterized as strength weakening and softening as subjected to external loading or soaking in water. As a result, engineering problems, such as collapse of foundation pits, failure of CDG soil slopes, etc., take place quite often. To fully understand the mechanism of the above problems, a study on the CDG soil is carried out using the advanced X-ray CT scanning and geotechnical loading apparatus in a multi-scale, including: firstly, the characteristic of CDG soil structure is measured in a micro- and meso- scale, and its correlation with the mechanical properties is established. Secondly, the evolution process of the internal structure of CDG soil under the loading and soaking condition is studied using the CT scanning and geotechnical test apparatus, and the occurrence and expansion of the soil crack are feature classified and quantified as well as the main controlling factors of microstructure damage factors that influenced the macro-mechanics. Thirdly, the damage factor characterizing the change of soil structures is introduced for set up the damage constitutive model of CDG soil. This research will provide a reference for better understanding the mechanism of the weakening and softening of the CDG soil under loading and/or soaking and contribute to the future engineering practice.