A Study of the Mechanics of Coal Mine Rib Deformation and Rib Support as a basis for Engineering Design.

Colwell, Mark Gerard (2006). A Study of the Mechanics of Coal Mine Rib Deformation and Rib Support as a basis for Engineering Design. PhD Thesis, School of Engineering, University of Queensland.

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Author Colwell, Mark Gerard
Thesis Title A Study of the Mechanics of Coal Mine Rib Deformation and Rib Support as a basis for Engineering Design.
School, Centre or Institute School of Engineering
Institution University of Queensland
Publication date 2006
Thesis type PhD Thesis
Abstract/Summary With an increasing focus on safety in the Australian underground coal mining industry and government legislation requiring employers to provide a safe workplace, there is a clear need for today’s strata control engineers to have design capabilities in relation to coal mine rib support that provide effective, reliable and consistent solutions. There has been a relatively limited amount of research undertaken with respect to the study of the mechanics of coal mine rib deformation and rib support and prior to this study no systematic rib support design technique had been developed for any country’s underground coal mining industry. This is in direct contrast to other geotechnical issues, such as coal mine roof support and pillar design, which have been extensively researched resulting in numerous technical papers, conferences/workshops dedicated to these specific issues and several proposed design techniques and/or guidelines. It is assessed that the primary reasons for this disparity have been a lack of understanding concerning the failure mechanisms associated with ribline behaviour and not being able to delineate the significant factors that affect ribline behaviour. This thesis has investigated the mechanical behaviour of coal mine ribs under various loading environments and with a wide variety of rib support hardware as a basis upon which an engineered design methodology could be formulated. A program of full scale field trials were conducted at ten collieries (representing four of the five major Australian coalfields), in conjunction with a comprehensive industry wide review of ribline performance from which a database was formulated and statistically analysed. The results of the field based experimental program and statistical analyses strongly suggest that the mechanical nature of rib movement is consistent with the buckling of thin coal plates or slabs. While a precursor to buckling may be tensile failure in the form of vertical splitting along cleat, mining induced fractures (as a result of roadway development) or the formation of new cracks due to longwall abutment loading; it is clear from the extensometry that the nature and magnitude of the lateral displacement is a result of buckling. There was a significant reduction with respect to the extent of softening within the riblines that utilised areal support in the form of steel or plastic mesh. The major structural or mechanistic benefit of mesh to overall ribline performance is that it maintains the buckled coal plate to the ribline allowing it to behave (to a degree) like a spring, which in this instance not only provides resistance to the vertical stress but also provides an active lateral force to the inner coal plates. Essentially the best rib support in terms of overall roadway maintenance is potentially the rib itself. Based on the results of this study and an improved understanding of the mechanistic behaviour of coal mine ribs, a design methodology (the first of its type), known as Analysis and Design of Rib Support (ADRS), has been developed for the Australian underground coal mining industry. Since its release to the Australian collieries in February/March 2005 via ACARP technology transfer workshops, ADRS has now been registered and successfully used by most Australian collieries, the NSW Mining Inspectorate and several consultants. ADRS is an empirical technique, which recognises that several geotechnical and design factors affect ribline performance and in addition that operational and safety issues essentially dictate the level of performance required. Therefore the design recommendations associated with ADRS are specific to the Australian coal industry; however the procedure(s) for data collection and analysis could be applied to other countries’ underground coal industries.

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Created: Fri, 21 Nov 2008, 14:55:34 EST