Assessment of Rock Engineering Risk Management Frameworks Used in Underground Mines

Abstract

Over 40% percent of the accidents encountered at Unki Mines are related to ground failure and other geotechnical complications. This research sought to address the monetary losses incurred in revenue and productivity through absenteeism and injury. With the development of mine production in Zimbabwe, the depth of mines gradually increased, and the ecological environment developed complex conditions. Deep mining unlike shallow mining is characterized by extra ground pressure, more gas, and faster deformation rates. These factors affect the safety of mining production. Therefore, as the mining depth and breadth increase, the difficulty of mine rock engineering is also increasing. The deepening of mining depth and the improvement of the mechanization level have brought increasing difficulties regarding the stability of surrounding rock hence risk issues arise. The ultimate objective of this study was to ensure a robust design of support systems at Unki Mine that would eventually reduce the risks associated with rock engineering excavations. Findings from the study and its analysis established the following conclusions. On the fore is the fact that hanging wall instability at Unki Mine are predominantly governed by geological and span attributes. The computed k value is 7% less the k value of 57.33 MPa used for existing pillars. An analysis of FOS and its relationship with recovery and Pillar W/H ratio shows that over-break has a huge impact on the span stability hence the effect of the ANFO need to be reviewed for an alternative explosive that ensures recovery within 80% range to ensure that the FOS is maintained above 1.6.  A decrease in FoS increases the probability of failure, hence it is also important to device a pillar support system that is less prone to effects of over-break since the ground conditions are poor.