Three Hinge Buckling Stability of Laminated Rock Masses

In September 1989, a buckling (“pop-up”) failure occurred at Woods Sand and Gravel Quarry in Kingston, ON (Crossley, 1991). This resulted in flooding of the quarry and significant impact on the local groundwater conditions (e.g. neighbouring wells went dry). Buckling failures have commonly arisen in southern Ontario and the mid-western U.S. and typically develop suddenly, with little warning, driven by high horizontal in situ stresses in the stiff, laminated, near-surface rock. As a result, the Ontario Ministry of Environment and Climate Change (OMECC) has requested quantifiable assessment of rock buffer thickness (the separation between quarry floor and underlying aquifer) for future quarry development on the basis of fundamental engineering principles and site specific conditions (Kinney, 2013). Pop-up buckling, also referred to as three hinge buckling (THB), tends to occur violently in laminated rock slabs containing frequent cross-jointing that allows for the formation of a central hinge and two abutment hinges. THB is also a significant stability issue for rock slopes, tunnelling and underground mining: wherever a significant span of laminated rock under high stress occurs near a free surface. Although many authors (Cavers, 1981; Diederichs & Kaiser, 1999; Roorda, Thompson, & White, 1982) have made progress in the study of buckling behaviour in rock mechanics, several key issues remain unresolved. At this time, there is no clear engineering methodology to evaluate quarry floor THB stability. This proposed research program will investigate THB stability with a short-term focus on quarry floor stability, and a long-term focus on a broad range of relevant applications in mining and civil engineering, such as rock slopes and underground openings. This will require a detailed understanding of the THB failure mechanism, the in situ stress conditions, the spatial distribution of rock mass properties, and any potential “trigger” mechanism (e.g., pore water pressure). The research program will utilize physical modelling (laboratory-scale THB physical modelling), advanced numerical modelling (discontinuum) and recent rock mechanics developments to study THB stability. The results will have practical, directly applicable implications for the Canadian mining industry, regulatory agencies, and the general public.