关键词: 页岩, 巴西劈裂, 含水率, 层理, 3DEC

Abstract: To analyze the effects of bedding and water on the tensile strength of shale, specimens with four water contents were prepared with Longmaxi Formation black shale. Brazilian disc splitting tests were carried out on prepared specimens along the angles of 0°, 30°, 60° and 90°. Acoustic emission tests were simultaneously performed during the experiments, and results were further simulated by the discrete element software 3DEC. The results show that, compared with the bedding shale, the shale with both water and bedding presents a unique failure mode and special mechanical properties. Both the fracture pattern and tensile strength of Brazil shale ae related to the bedding angle and water content. Particularly, the failure mode is mainly controlled by the loading direction of bedding. Although water do not affect the failure mode, it lead to the formation of secondary cracks. The tensile strength firstly decreases and then increases with increasing the bedding angle, while it decreases with increasing water content. Moreover, under the combined effects of water and bedding, the more the shale is damaged by the bedding, the higher it is damaged by the water. The mechanism of the above changes is obtained based on the analysis of the microstructure of the shale at different water contents. When the internal mineral particles are swollen with water at the surface of the shale, the expansion force is generated, and internal structure of the shale became loose and broken. Furthermore, microcracks gradually increased and broadened. The macroscopic performance accounted for the increase of secondary cracks. In addition, the bond strength between mineral particles is also reduced under the action of water, which further decreases the tensile strength of shale.

Key words: shale, Brazilian test, moisture content, bedding, 3DEC