三峡库区侏罗系泥岩CT损伤特性试验研究

Research on CT damage characteristics of the Jurassic mudstones in the Three Gorges Reservoir area

结合CT-三轴试验研究了三峡库区侏罗系泥岩破坏过程中的细观损伤特性。获得了泥岩受破坏时的实时CT图像、CT数均值及方差等结果。通过CT图像中泥岩内部的主裂纹区域和非主裂纹区域在变形破坏过程中出现的特征,采用截面整体分析和选取区域分析相结合的方法探讨了岩样各变形阶段的损伤演化规律。研究表明:宏观裂纹一般最早出现在到达屈服点后,形成于红层泥岩承载能力较弱的区域,即原生孔隙、微裂纹较集中的区域,根据岩石内部区域CT数的变化规律可以判断裂纹的出现阶段和损伤程度。基于此,提出将不同围压下泥岩在屈服点的应变值作为岩石损伤的门槛应变值,低于该应变值时,侏罗系泥岩无明显损伤,高于该应变值时,损伤加剧。

The meso-damage characteristics of the Jurassic mudstones in Three Gorges Reservoir area are studied under different confining pressures though the CT-triaxial test. The CT images,average of CT-number and variance of CT-number in real-time are obtained from the test. In view of the formation characteristics of the main crack zone and the none-primary crack zone of CT images under different deformation phases,the analysis method of the whole section and the selected area are used to discuss the damage evolution of the mudstones in each deformation phase. The results show that the initial macro-crack appears after the yield point,and it forms in the area of the weaker bearing capacity. According to the law of the CT-number changes of some areas,the emerging stage and damage degree of crack can be estimated. This paper puts forward the strain value of the yield point under different confining pressures as the threshold strain value of rock damage.The rock sample has no obvious damage when strain is below the threshold strain value,and the damage becomes worse when strain is above the threshold strain value.