M. Ing. / Managing the risks to life and limb and to the environment due to potential accidents and structural failures during the lifecycle phases of a TD is a complex, intricate and dynamic process, because of the sheer number of hazards that are involved. Fault and event trees enable one to systematically identify these hazards within the context of their intricate relationships. An internationally accepted qualitative scale enables one to assign probabilities in terms of engineering judgement to the sub-causes in the fault trees and the probabilities of the top faults to be calculated. Mine and industry accident statistics enable one to assign relevant frequencies to the subtended event trees and to determine the resulting probabilities of fatal injury or environmental damage. An internationally accepted relationship between lifetime probability of failure causing death and the potential number of fatalities enables one to determine whether the resulting probability of fatal injury is acceptable. If such resulting probability of fatal injury is not acceptable, the biggest contributing subcauses in the underlying fault tree can be identified and mitigating measures considered on an optimal cost benefit basis. The fault trees for the different life cycle phases of the TD also enable one to take cognisance of the dynamic changes in the frequencies of the sub-causes in the various phases and how the risk management focus may change over the life of a TD although the overall threat may not necessarily vary very much. During investigation of the causative modes for personal injury due to mine accidents/hazards at or on the TD it was found that the probabilities associated with fatal injury during the life cycle phases considered were acceptable. The sensitivity of the factors was however investigated further to provide confidence, and event and consequence trees were developed for TD road accidents which were identified as having the highest probabilities of occurrence. The most efficient risk management intervention measure evaluated was found to be increasing compliance with the mine’s road traffic safety regulations. Investigation of the causative modes for personal injury due to structural failure of the TD determined that the probabilities associated with fatal injury were acceptable and no risk mitigation measures were thus required. The causative modes for environmental damage due to mine accidents/hazards were examined next and the probabilities associated with environmental damage were found to be unacceptably high for the life cycle phases considered. Risk management intervention 57 measures were thus required to lower the associated risks to acceptable levels based on relevant and realistic environmental protection guidelines. No mitigation measures were developed as part of the study. Causative modes for environmental damage due to structural failure of the TD were investigated last. The probabilities associated with environmental damage during the life cycle phases considered were also found to be unacceptably high. Risk mitigation measures were thus required but none were developed as part of the study. Fault and event tree methodology as employed in this study can thus be used as valuable supporting instruments for investigating the causative failure modes of a complex system, the identification of potential risk mitigation measures, and for evaluation of the effectiveness of the proposed risk management measures.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:2357 |
| Date | 04 June 2012 |
| Creators | Otto, Hendrik Johannes Hertzog |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
Page generated in 0.0021 seconds