Investigations on the jointed influences of saturation and roughness on the shear properties of artificial rock joints

Natural rock joints are rarely dry or saturated. It is therefore essential to quantitatively assess the influence of varying saturations on shear properties of rock joint. In this study, to guarantee the test repeatability, artificial rock joints with various roughness coefficients (JRCs) of 0, 7.3, 10.1, and 12.9 are firstly reproduced by utilizing rock-like materials. Then, direct shear experiments are performed on the duplicated joint samples at various moisture conditions ranging from dry to saturation, while under a constant normal stress of 0.2 MPa. Obviously, it is noticed that the shear strength of joint sample declines with an increment in joint saturation. Specifically, when compared to the corresponding dry samples, peak shear strength (PSS) of saturated samples with JRCs of 12.9, 10.1, and 7.3 decrease by 35.7, 28.5, and 16.1%, respectively. Moreover, the observed weakening influence of joint saturation on its PSS is roughness sensitive, which may be resulted from the changing in water-rock contact areas of joints with different roughness. Besides, the residual shear strength is also observed to decline as joint saturation increases. Furthermore, based on experimental results, a correction factor is proposed and introduced into the classical JRC-JCS shear strength criterion, and the corrected criterion is capable of estimating peak shear strength of joint sample subjected to various saturations. This work can provide some insights into the shear strength evolution of rock joints under varying saturations, and the findings emphasize the importance of considering the moisture content in rock engineering where wetting phase is encountered.