澳门银河赌场注册送38-澳门银河赌场招人好招吗_百家乐德州_全讯网下载 (中国)·官方网站

Abstract: It is inadequate to study the shear failure anisotropy of shale in only 2D space. Aiming at a 3D analysis, a series of direct shear tests was conducted on Longmaxi shale with three typical bedding orientations: arrester, divider and short-transverse orientations. During testing, acoustic emission (AE) and digital image correlation (DIC) techniques were simultaneously employed to monitor failure development, after testing, X-ray computed tomography (CT) scanning was adopted to acquire and reconstruct the fractures inside typical ruptured samples for more detailed analysis. The results indicated that the shear strength parameters exhibited 3D anisotropies and those of the arrester sample did not have equivalent shear strength parameters to the shale matrix. The maximum (minimum) shear strength and cohesion were obtained with the divider (short-transverse) orientation, and the internal friction angle reached its maximum (minimum) with the divider (arrester) orientation. Combining the AE, DIC and CT techniques, four characteristic stress levels that can capture the progressive shear failure process of shale rocks were identified, and the onset and accelerated development of shear damage-induced dilation were observed at the crack initiation and coalesce stress thresholds, respectively. During the crack coalescence stage, the dominated microcracking mechanism transferred from tensile-mode to shear-mode. For the arrester and divider orientations, more tensile-mode AE events were generated due to the microcracking along the vertical beddings. Compared with the divider samples, a more complex fracture network with a larger fracture area and volume was obtained in the arrester samples, whose strengths were smaller.