Impact of shaft steelwork on grain size distribution of filling material during shaft closure based on the DEM simulations

Improper shaft closure is often indicated as a cause of stability loss in old shafts and the associated damage to surface facilities. Currently, the most commonly used method of shaft closure is filling the shaft with a grainy material. Unfortunately, during the shaft closure, the selected filling material degrades, and the composition of the grain size changes. The magnitude of those changes depends on many factors, such as shaft depth or feeding method. The results of numerical analysis indicate that the degradation of the grains may also be influenced by the presence of steelwork in the shaft (e.g., buntons or compartment ladders) that, due to economic reasons, is increasingly not removed before shaft closure. The numerical modelling was performed using the Bonded Particle Model implemented in the PFC3D code.