Geological structural controls on stability of footwall slopes: an example from the Bowen Basin, Queensland
Published:January 01, 2016
D. Pope, A. Duran, G. Grocott, O. Holm, A. Bell, 2016. "Geological structural controls on stability of footwall slopes: an example from the Bowen Basin, Queensland", Developments in Engineering Geology, M. J. Eggers, J. S. Griffiths, S. Parry, M. G. Culshaw
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Surface mining of coal can involve extensive footwall slopes parallel to shallow to moderately dipping coal measures strata. Footwall failure mechanisms typically invoke bedding-parallel defects but also require either the existence of flatter structures, which cross-cut bedding, or require break-out through the rock mass to allow failure surfaces to emerge.
Permian-aged Baralaba Coal Measures of the Bowen Basin, Queensland, are prospective for coal with extraction by open-pit methods. The Baralaba Coal Measures contains multiple seams within an interburden sequence comprising sandstone, siltstone, mudstone and carbonaceous variations. The coal measures sequence has been deformed into a complex pattern of NW-striking folds which has resulted in bedding dip ranging from 15° to 60°. Bedding has been classified as shallow (10–30°) to moderate (30–60°).
Geotechnical investigations conducted to support coal extraction up to depths of 200 m suggest that structural controls strongly influence footwall slope design. For the purpose of footwall slope design, a distinction can be made between deposit areas of relatively simple structure (uniformly dipping bedding on fold limbs) and structurally complex areas (where layer-parallel shortening close to fold hinges has resulted in a system of low-angle thrusts and asymmetrical minor folds).
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Developments in Engineering Geology is a showcase of the diversity in the science and practice of engineering geology. All branches of geology are applicable to solving engineering problems and this presents a wide frontier of scientific opportunity to engineering geology. In practice, diversity represents a different set of challenges with the distinctive character of the profession derived from the crossover between the disciplines of geology and engineering. This book emphasizes the importance of understanding the geological science behind the engineering behaviour of a soil or rock. It also highlights a continuing expansion in the practice areas of engineering geology and illustrates how this is opening new frontiers to the profession thereby introducing new knowledge and technology across a range of applications. This is initiating an evolution in the way geology is modelled in engineering, geohazard and environmental studies in modern and traditional areas of engineering geology.