This study investigated the effect of the layer orientation on fracture propagation of Longmaxi shale under in situ uniaxial compression loading scanned by micro-computed tomography (CT). We conducted ten cylindrical specimens (4 mm diameter and 8 mm height) with bedding plane inclined at 0° and 90° to the axial loading direction, respectively. The results show typical brittle fracture characteristic and heterogeneity of mineral composition of the miniature shale specimens. The average value of UCS of specimens at 0° is little lower than those of specimens at 90°, while average elastic modulus (E) at 0° is slightly higher than the latter. Based on reconstructed three-dimensional CT images threshold segmentation of cracks, cracks occur earlier in specimen at 0°, mainly in the form of tensile splitting parallel with axial loading direction, while shear sliding oriented at an angle of about 65~75° to the horizontal direction dominated in the specimens at 90°. Besides, according to scanning electron microscopy(SEM) observation of microstructure characteristics, it is demonstrated that the fractured bedding plane appear to be more flat and smooth than the cross section. The failure mechanisms at 0° is more prone to be intergranular fracture along the weak consolidation, while transgranular fracture is the main attribution of failure at 90°. Moreover, box-counting dimension(BCD) calculations on processed three-dimension images of cracks also proved a larger degree of complexity and roughness at 90°.
Presentation Date: Monday, September 25, 2017
Start Time: 2:15 PM
Location: Exhibit Hall C/D
Presentation Type: POSTER