Developing a ground control strategy for squeezing conditions in hard rock mines

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A large number of underground hard rock mines are exposed to large scale deformation often referred as squeezing ground conditions. This has major economic and safety implications for the mining industry especially where deeper excavations are developed. The majority of tools used to estimate the susceptibility of excavations to closure are based on empirical data from civil engineering tunnels in weak rock. Rock masses composed of weak rock tend to behave in a nearly isotropic fashion even when highly foliated. Excavations in foliated hard rock are more susceptible to anisotropic behaviour. The levels of what is considered acceptable squeezing in a mining environment are quite higher in a mining environment as opposed to tunnelling. This allows some more flexibility to operators. On the other hand, mines have to work with what are considerably higher constraints in the choice of economic support. Squeezing ground conditions in mines are characterized by significant failure of ground support systems that often necessitates considerable rehabilitation work. This project addresses squeezing rock challenges at two underground Canadian mines owned by Agnico-Eagle Mines Ltd: LaRonde and Lapa. Both mines are located in the Abitibi region of Northwest Quebec and are facing large rock mass deformations. Of interest is that the two mines, located 11 kilometres from each other provide a large spectrum of squeezing ground control conditions.