Assessment of frictional resistance of granite rock joints with reference to weathering

摘要

Shearing resistance of rock joints is considered as one of the key aspects of rock masses as it is related to the stability of rock mass particularly at shallow surface condition. The shear behaviour of rock joints depends upon a number of influencing parameters and weathering state of discontinuity surface is one of them. However, over the years of research, the said issue has not been explored much. Hence this research presents primary findings aimed to explore the shearing resistance of unfilled rock joints regarding granites of different weathering grades. Multistage CNL direct shear tests were performed on six natural granite rock joints of two different but adjacent weathering grades at three different normal stress conditions ranging between 0.21 MPa - 0.7 MPa. It should be noted that the weathering grade of discontinuity surface was categorized following the six-fold weathering grade classification scheme, which was also substantiated with Schimdt rebound values. The data obtained from shear test was analysed in terms of stress ratio and peak friction angle, which shows the adverse effect of weathering with increasing normal stress condition. However, at low normal stress condition, such consequences were not significant.