ABSTRACT: As per most other earth science engineering problems, the underground coal geotechnical environment and the way in which roof and rib support interacts with the rock mass are complex issues. It is therefore generally recognised that without prudent simplification, the complexity of the problem will overwhelm all current geotechnical methods of modelling, not least for the reason that a rock mass can never be characterised to a level that allows a “non-simplified” analysis. The fact that numerical models, which are commonly purported to be a “simulation” tool and the so-called epitome of advanced geotechnical engineering, always need to be “calibrated” to a known reality is taken to be conclusive proof of this statement.
While the problem should not be oversimplified (i.e. the dominant failure mechanisms or critical data input parameters should not be ignored), without question judicious simplification is at the heart of all engineering design, to the point that it has a well-established name – “reductionism”.
This paper demonstrates that slender beam/column behaviour is the dominant instability mechanism within a coal mine roof/ribline subject to elevated horizontal/vertical stress conditions and must be representatively accounted for in any credible empirical, analytical, or numerical approach to coal mine roof/rib stability assessment and associated ground support design.
The process by which the mathematical equations associated with slender beam behaviour (including buckling due to axial loading) can be readily accommodated as a part of geotechnical assessment and design is explained. Ensuring that the mathematical modelling/equations are representative of the problem being analysed, is crucial within many branches of science such as spaceflight trajectory/analysis. As that field of science has demonstrated, if the mathematics are wrong or necessary mathematical equations/code are missing, then the model can be worthless or even dangerous leading to disastrous results, which for the coal industry essentially means compromising the safety of underground workers with inadequate ground support designs.