Simmons, JV & Simpson, PJ 2007, 'Extension, Stress and Composite Failure in Bedded Rock Masses', in Y Potvin (ed.), Slope Stability 2007: Proceedings of the 2007 International Symposium on Rock Slope Stability in Open Pit Mining and Civil Engineering, Australian Centre for Geomechanics, Perth, pp. 213-223, https://doi.org/10.36487/ACG_repo/708_11
(https://papers.acg.uwa.edu.au/p/708_11_Simmons/)
Abstract: The mechanism of composite deformation in open pit coal mine slopes combines slip along existing defects 
with strength mobilisation involving rock material. Mining activity and initial stress conditions are linked 
with the onset of relatively sudden, unpredicted failures. In order to develop more reliable methods for 
recognising potential failure and providing early warning signs, it is first necessary to identify and 
understand the potential trigger processes. This paper describes early progress in numerical modelling of 
bedded coal measures rock masses under conditions where composite slope failures have occurred 
repeatedly. Results to date illustrate the effects of initial stress on extensional deformations within a highwall 
slope. The results are linked to observations of actual failures, and highlight the role of extension strain 
fracturing near the slope toe as a triggering mechanism.