花岗岩残积土复杂次生裂隙的分类与损伤特征

Classification and damage characteristics of complex secondary cracks in granite residual soil

裂隙的萌生、拓展演化对土体的损伤与破坏至关重要。为了研究岩土工程性状复杂的花岗岩残积土在荷载作用下内部细观裂隙的演化规律,利用CT扫描土体的三轴压缩过程,获得一系列重构数字体图像;引入裂隙体积重叠率用于改进笔者提出的裂隙分类方法,提高其在判断变形前后两裂隙团连通性的准确性。研究结果表明:裂隙体积重叠率的变化对湮灭型裂隙和新生型裂隙影响轻微,但对其余类型裂隙有不同程度的影响,表现为试样变形越大其影响也越大,综合选取裂隙体积重叠率为0.05时具有较好效果。随着轴向加载的增大,其中湮灭型裂隙和新生型裂隙的体积含量随着轴向应变的增大而增大,且新生型裂隙的体积含量增长更快,而复合型裂隙的体积含量呈衰减趋势,其余3种裂隙的体积含量均较小。通过分析不同类型裂隙的分形特征显示,裂隙的分形维数与体积含量变化相似,其中湮灭型裂隙、新生型裂隙和合并型裂隙呈增长趋势,新生型裂隙的分形维数增长最快,说明新生型裂隙更能够反映试样的剪切破坏过程。该研究成果将为岩土体的裂隙损伤分析提供理论与技术支持。

The development of cracks is important to the damage and failure of soil.In order to study the evolution of meso-cracks in granite residual soil with complex geotechnical engineering properties,a series of reconstructed volume images was obtained by using CT to scan the process of the triaxial compression test.The crack volume overlap rate is introduced to improve the crack classification method proposed by the author,and the accuracy of judging the connectivity of the two cracks before and after deformation is improved.The results reveal that the change of crack volume overlap rate has a slight effect on the obsolete and brand-new cracks,while the greater sample deformation leads to the greater influence on other types of cracks,and the optimal crack volume overlap rate is 0.05.The volume content of obsolete and brand-new cracks increases with the increase of axial strain,and the volume content of brand-new cracks increases faster,while the volume content of compound cracks decreases,and the volume content of the other cracks is small.The change of fractal dimension of cracks is similar to that of volume content.Among them,obsolete,brand-new,and combined cracks show an increasing trend,and the fractal dimension of brand-new cracks increases the fastest,indicating that brand-new cracks can better reflect the shear failure process of samples.The results will provide theoretical and technical support for the fracture damage analysis of geomaterial.