Evaluation of the required strength of cemented backfill with a vertical open face: a revisit to Mitchell’s physical model tests
Dr Guo Lijie (Deputy Director - Institute of Mining Engineering, Beijing General Research Institute of Mining and Metallurgy), Mr Guangsheng Liu ( - École Polytechnique de Montréal), Mr Yang Xiaocong (Director - Institute of Mining Engineering, Beijing General Research Institute of Mining and Metallurgy), Prof Li Li (Professeur agrégé - École Polytechnique Montréal)
Backfill is increasingly used in underground mines world-wide. It can be used with several mining methods. Some of these require an evaluation of the minimum required strength of cemented backfill vertically exposed by the excavation of an adjacent stope on one side. This task is usually completed by using a solution proposed by Mitchell and co-workers in the early 1980’s. More than thirty years later, despite its wide acceptance in academia and industry, it has received only a few updates in the literature, including some new developments given by the author and co-workers. It is noted that the original Mitchell et al. solution and its variants were mainly validated against a series of physical model tests performed by Mitchell and co-workers in 1982. It is also noted that the required strengths predicted by the Mitchell et al. solution correspond fairly well to the experimental results even though the Mitchell model debatably assumed a zero backfill friction angle. How to explain this? Is it a coincidence? In this paper, a revisit to the Mitchell et al. solution and their physical model tests is presented. Focus is given on the testing conditions of their physical model tests. The stability of the cemented backfill upon removal of a confining wall is analyzed by numerical modelling with FLAC3D. The comparison between the numerical modelling and experimental results will be presented and discussed.