Consolidation in accreting sediments: Gibson's solution applied to backfilling of mine stopes

There is increasing use of hydraulically placed tailings backfill in mined-out voids (‘stopes') in underground mining, with the backfill being retained in the stopes by barricades built across the stope access tunnels. The forces acting on these barricades depend on the degree of consolidation that occurs during the backfilling process. A solution to the problem of consolidation in a layer increasing in thickness owing to ongoing sedimentation was proposed by Gibson in 1958. This solution appears to be directly relevant to the stope backfilling process, although there are limitations in applying it. Using material properties from two mine sites, the applicability of the Gibson solution to stope filling is examined. In particular, since one of the basic assumptions of the Gibson solution (that c_v remains constant during filling) is generally violated, the effect of having a varying c_v is explored using numerical modelling. Finally, the limitations of applying the Gibson solution to the stope backfilling problem are discussed. These relate particularly to the three-dimensional nature of stope geometry and drainage (compared with the assumption of one-dimensional conditions in the Gibson solution) and the fact that cement is generally added to backfill, such that the analysis herein is only valid up to the start of cement hydration.