Numerical analysis of the time-dependent response of backfilled mine openings in soft rocks

ABSTRACT: Backfilling is commonly used in underground mines to improve ground stability. Mine backfill can also serve to control wall convergence and maintain the integrity of pillars by adding local support. The design of backfilled openings requires an evaluation of the stress state in the filling material and surrounding rock mass. To date, most analyses of the stress distribution in and around backfilled openings have been performed for hard rock mines with little deformation of the walls after fill placement. The analysis however becomes much more complex when the rock is subjected to significant time-dependent (creep) behavior as is often the cases in many soft rocks (rocksalt, potash). This article presents some results from recently conducted simulations to assess the interaction between creeping rock and the backfill placed in mine openings. The simulations are performed with FLAC with the time-dependant ISV-SH model. Numerical modelling results are used to evaluate the evolution of the strain and stress distributions due to transient and steady-state creep in underground backfilled openings, considering different geometries and properties. A brief discussion follow.