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State of the Art Dimensioning of Shield Support to Optimise... |
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State of the Art Dimensioning of Shield Support to Optimise Longwall Roof Control Authors: U. Langosch, U. Ruppel
Basic rock-mechanics research has always set itself the target of improving roof control measures
at the coal face. The results of this work frequently led to the development of new support equipment.
Between 1999 and 2003 a series of underground investigations was carried out as part of a DSK R&D
project whose aim was to predict the roof fall frequency and from this to determine the roof control measures
required at the longwall face, with a view to submitting recommendations for the operation of the
production faces. The interpretation of the coal-face observations yielded the following results:
– The geological-geotechnical features and characteristics of the roof strata call for a critical distance
between the tip of the shield support canopy and the coal face; only if this critical tip-to-face distance
is exceeded can roof falls occur. In order to prevent roof falls the shield supports have to be specifi cally
chosen for each face in such a way that the critical tip-to-face distance is never exceeded under any
operating conditions.
– If the tip-to-face distance is allowed to exceed the critical threshold, the frequency with which roof
falls occurs can be predicted using an empirical equation.
From time to time, however, the strata are stressed to such a degree that the technical capabilities of
the support system are not suffi cient to keep within the critical tip-to-face distance. Roof falls will then
be unavoidable. This set of circumstances produces a further set of planning requirements.
– Where in the strata is there a suitable layer of rock above the coal seam for optimum roof control?
– Will the extension range of the supports still be suitable for this strata layer?
The paper provides answers to these questions, presents the results of the recent R&D work and uses
practical examples to explain how these state of the art calculation methods can be used. |
2011