Review of Major Hazards Risk Assessment in a Scottish Underground Mine

Occupational health and safety is relevant to all branches of industry, business and commerce. All fatal accidents and injuries can be avoided, all hazards can be identified, and their risks managed. This work of thesis aims to analyse the major hazards within an underground mine in the Scottish Highlands, managed by Lochaline Quartz Sand L.t.d. Lochaline mine is the only underground sandstone mine in Europe. The huge deposit of pure white sandstone is exploited by rooms and pillars method and extracted by drill and blast technique. All mining operations are carried out following Health and Safety Executive regulations. An underground mine can be a hazardous workplace. In the Lochaline mine the five major hazards are represented by vehicle impacts, unplanned explosion, water inrush, underground fire and the roof failure. This work provides the 2022 update of the evaluation and the management of these five major hazards using the Bow Tie method. The Bow Tie is the risk evaluation method used in the mine to investigate cause-effect relationships in the five major hazards scenarios and it is updated, reviewed, and improved, compared to the previous version of 2019. During the end of 2021 roof failure issues occurred in the mine and thus the study is focused on this most risky hazard, with the aim to understand the causes which could lead to a roof failure in the mine. The issue is addressed using the numerical modelling software FLAC 3D, with which a volume of rock of the mine is simulated and the state of stress in the roof is analysed. The analysis is then repeated, by varying some leading geotechnical parameters in a reasonable range, to identify which combination could generate a state of stress in the roof, such as to exceed the rock strength and lead to a failure. The results from this analysis, in terms of Factors of Safety, provide better knowledge of roof failure hazard inside the mine, and confirm the roof support design choices, employed by the company, to manage it.