Document Type

Conference Paper

Publication Date


Publication Details

Elizabeth Downing, Ali Mirzaghorbanali and Naj Aziz, Shear strength properties of clean and clay infilled rock joints: an analysis of the impast of moisture content under CNL conditions, Proceedings of the 2023 Resource Operators Conference, University of Wollongong - Mining Engineering, February 2023, 250-267.


Rock joints are a type of fracture or discontinuity that have little or no movement that is parallel to the plane of fracture caused by forces acting perpendicular to the fractured walls, where the opening of the break is parallel to the face of least resistance. These are common phenomena in geology around the world and range from small scale to tectonic fault lines. The first part of this project focused on the effect of clean rock joints on the shear strength of the joint at normal loads of 100, 300, 500 and 700 kPa. Rock joints leave an opportunity for infill to occur in the form of soil, water, or mineral precipitates. The second part of this project focuses on the effects of sodium bentonite clay infill with moisture contents of 0%, 10% and 16% and normal stresses of 100, 300, 500 and 700 kPa on the shear strength properties of rock joints. As shear strength is a controlling factor for slope stability, it is important to continue research into this area in order to optimise future engineering project outcomes. There are two main loading conditions for the direct shear testing of rock joints; Constant Normal Loading (CNL) and Constant Normal Stiffness (CNS). As CNL and CNS conditions are representative of different real-world applications it is critical to understand the scope and context of each investigation. This project was conducted under the CNL boundary condition as it predominately focuses on the impact of moisture content on the shear strength of rock joints under unsaturated conditions. These conditions are more likely to occur in shallow rock formations due to the infill and moisture fluctuations that are caused by water infiltration and precipitation.