Shear Model Development of Limestone Joints with Incorporating Variations of Basic Friction Coefficient and Roughness Components During Shearing
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In relation to the shearing of rock joints, the precise and continuous evaluation of asperity interlocking, dilation, and basic friction properties has been the most important task in the modeling of shear strength. In this paper, in order to investigate these controlling factors, two types of limestone joint samples were prepared and CNL direct shear tests were performed on these joints under various shear conditions. One set of samples were travertine and another were onyx marble with slickensided surfaces, surfaces ground to #80, and rough surfaces were tested. Direct shear experiments conducted on slickensided and ground surfaces of limestone indicated that by increasing the applied normal stress, under different shearing rates, the basic friction coefficient decreased. Moreover, in the shear tests under constant normal stress and shearing rate, the basic friction coefficient remained constant for the different contact sizes. The second series of direct shear experiments in this research was conducted on tension joint samples to evaluate the effect of surface roughness on the shear behavior of the rough joints. This paper deals with the dilation and roughness interlocking using a method that characterizes the surface roughness of the joint based on a fundamental combined surface roughness concept. The application of stress-dependent basic friction and quantitative roughness parameters in the continuous modeling of the shear behavior of rock joints is an important aspect of this research.
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An Experimental Study on Normal Stress and Shear Rate Dependency of Basic Friction Coefficient in Dry and Wet Limestone JointsMehrishal, S.; Sharifzadeh, Mostafa; Shahriar, K.; Song, J. (2016)© 2016 Springer-Verlag Wien. Among all parameters that affect the friction of rocks, variable normal stress and slip rate are the most important second-order parameters. The shear-rate- and normal-stress-dependent friction ...
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