Roughness variation of rock joints during shearing and associate acoustic emission characteristics

• Main Authors: Yu-Hsiang Hsiao, 蕭宇翔
• Other Authors: Tai-Tien Wang
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/ncqa5q

碩士 === 國立臺北科技大學 === 資源工程研究所 === 99 === Weak planes such as joints and discontinuities existing a rock mass may decrease strength and increase deformation of the rock. The mechanical properties of rock joint control the engineering properties of a rock mass, while roughness characteristics mainly dominate the mechanical properties of rock joint. Thus, the roughness induced complex shearing behavior for a rock joint remains an important branch among the research topics in rock mechanics. To better understanding mechanical characteristics and acoustic emission behavior of rock joints, this study utilizes the law of simulation to reproduce the rock-like artificial materials as testing samples. A kind of gypsum with a compressive to tensile strength ratio of 3.65, a deformation module to uniaxial compressive strength ratio of 250, a Poisson ratio of 0.19 and a basic friction angle of 38.8˚ is used. Regular joints with saw-tooth of 0˚ and 15˚ and rough joints with JRC of 6-8, 10-12, and 18-20 are prepared for tests. The shear test results of regular joints show that peak shear strength as well as corresponding peak shear displacement increase as the increase of normal loading, and both the post-peak strength reduction and the stick sliding phenomena become significant as the increase of roughness and normal loading. The change of normal loading at distinct stage leads to different shear behavior. Increasing normal stress at prior peak non-linear stage, the shear stress increase stepwise as the increase of normal stress, significant post-peak strength reduction can be observed for regular joint but not for rough joint. Reducing normal stress at post-peak stage, the strength reduction is corresponding occurred, and the shear stress-displacement is similar to that one with similar normal stress. Furthermore, the instantaneous dilation becomes significant as the reduction of normal stress, and gradually reduces with shear displacement. In case the normal stress is increased at post-peak stage, the dilation remains constant and the shear stress reaches steady as the increase of shear displacement. The acoustic emission (AE) account is low during initial shear stage with low normal stress, and is increased as the shear stress approaching pre-peak non-linear stage. In case the normal stress is increased, the AE account is significant increased and prolong to post-peak stage due to the joint sliding failure pattern changing into asperities shearing-off pattern gradually. Comparing with joint shear test with constant normal stress, changing normal stress during shear will lead to more asperities shearing–off pattern. The failure pattern of joint under various normal stresses can be effectively understood via AE measurement and associated data processing.