Instability assessment of slopes in heavily jointed limestone rock

This paper presents the results of geotechnical investigations regarding the assessments of instability problems in the high wall slope faces of the heavily jointed limestone rock mass in Marulan Quarry in NSW, Australia. Generally, instability of hard rock slopes is mainly controlled by the presence of the structural geology and rock mass discontinuities through the slope faces of the open pit excavations. Stability analysis of slope faces in an open pit mine requires the laboratory assessment of the engineering properties of rock, shear strength of the discontinuities and also field investigations of the rock mass discontinuities. To achieve the above objectives, a laboratory testing program was carried out on the intact rock samples and also a three-dimensional scanline survey was carried out to consider the physical and mechanical properties of the rock mass discontinuities. The results of the discontinuity data collected during joint surveys were interpreted with the application of stereographic projection techniques for assessing the potential unstable zones and also for defining the modes of failure in different parts of the limestone quarry.