The influence of impact loads on the integrity of ore pass walls
Rock Engineering 2009 - Rock Engineering in Difficult Conditions
Material transfer in underground mines often relies on ore and waste pass systems. A common practice is the use of “finger raises” to funnel material into an ore pass intersecting two or more production levels. The drop of rock fragments, however, results in high impact loads acting on the walls of an ore pass. Empirical evidence suggests that this can damage the walls and, potentially, affect the structural integrity of an ore pass. This can lead to enlargement of the ore pass. This has been confirmed by cavity monitoring at several mine sites.
The extent of damage inflicted by impact loads is dictated by material transferred, finger and ore pass configuration, and the rock mass quality of the walls that absorb the impact. Important material characteristics include size distribution, particle shape, and hardness. The capacity of ore pass walls to resist impact loads is influenced by the rock mass quality and stress regime.
This paper investigates the influence of ore pass and finger configuration in mitigating damage due to impact loading on the ore pass walls. The paper reviews the current level of empirical knowledge and describes a series of numerical experiments to provide a better understanding of impact loading of ore passes. To these purposes the authors have employed the Particle Flow Code. This choice was justified based on earlier work whereby the Particle Flow was successfully used to investigate the development of hang-up and blockage phenomena in ore passes. The present work focused in determining the impact loads generated by rock fragments on the ore pass walls for a range of finger configurations. This has allowed the authors to establish a series of favourable finger inclinations with respect to an ore pass. Finally, the paper discusses the results of the numerical experiments with reference to field observations.