A holistic examination of the load rating design of longwall shields after more than half a century of mechanised longwall mining

It is a commonly asked question: how big should the longwall shields be? The answer is a key aspect of a longwall mining feasibility study when the consequences of inadequately rated shields are considered. This paper addresses this question based on the measured nature of the loading environment in which shields are required to operate, the various geological and geometrical controls of that environment and the various links between their load rating, a range of other relevant shield design factors and the loss event they are required to prevent a major roof collapse on the longwall face. The paper concludes that despite the tremendous advances that have been made in shield design and load rating over the past 50 years, the same drivers that caused longwall miners of the past to seek improved roof control on the longwall face via the use of ever-higher rated shields, are still as relevant today. However at the current time, the limits of the largest available longwall shields have yet to be tested, therefore industry focus for the foreseeable future should possibly be in achieving the maximum level of roof control on the face via their optimum operational use rather than considering further shield rating increases and incurring the inevitable downsides in terms of capital cost and shield weight.