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Abstract: This paper addresses the problem of obtaining the information to support rock mechanics modelling and rock engineering design. A large amount of relevant material exists worldwide on previous rock parameter determinations, modelling exercises, design work, and construction projects. However, the information learnt from these activities is not easily accessible and useable, i.e. there has been no attempt to develop a ‘corporate memory’ system for rock mechanics and rock engineering. A structure for such a system is outlined comprising tables of intact and rock mass properties, libraries of standard and case example modelling solutions, and libraries of design and construction case examples. The procedure for initial implementation of the memory system under the aegis of the ISRM is described. 1 INTRODUCTION When conducting rock mechanics modelling and incorporating the results into rock engineering design, it is clearly advantageous to use all the relevant techniques and information that are available. Currently, this is often not achieved because knowledge of the techniques and information is not readily available, i.e. there is no overall mechanism for recalling the relevant information. In other words, the modelling and design is not supported by a ‘memory system’. We will term this memory the ‘corporate memory’ or ‘organisational memory’ of the rock mechanics and rock engineering community. The thrust of this general description of the corporate memory requirement applies directly to rock mechanics modelling and rock engineering design and is the motiva-tion for the content of this paper. Those of us involved in rock mechanics use our memory extensively in the modelling and design process, from understanding the rock mechanics principles, to estimating typical rock properties from experience, to having expertise with computer programs, to knowledge of previous modelling exercises, to rock construction designs that have succeeded, and sometimes failed.
- Energy > Oil & Gas (0.46)
- Energy > Power Industry (0.46)
Abstract: This paper presents key concepts regarding the use of Limit State Design (LSD) in rock engineering. The last two decades has seen significant development in LSD principles for application in geotechnical engineering, with the result that they can now be routinely applied to designs involving soil. However, robust application of LSD seems to be not possible for designs involving fractured rock. We suggest that this is due to the uncertainty model that forms the basis of LSD, and hence Eurocode 7, being inappropriate for fractured rock. Eurocode 7 (EC7) requires that uncertainty in geotechnical properties is stochastic in nature, the so-called aleatory model. However, we show that this model is not always applicable to rock mass parameters, and that uncertainty is often due to insufficient knowledge or subjectivity – so-called epistemic uncertainty. Based on an understanding of these two uncertainty models, this paper discusses the shortcomings of EC7 to deal with epistemic uncertainty in the context of fractured rock masses, and emphasises the importance of firstly recognising the differences between aleatory variability and epistemic uncertainty, and secondly appreciating the implications of such uncertainty for rock engineering design to limit state concepts. Finally, we give pragmatic suggestions for how the epistemic uncertainty of rock mechanics properties may be incorporated in the current LSD paradigm. 1 INTRODUCTION Limit State Design (LSD) principles and codes are commonplace in structural engineering designs, and in order that geotechnical designs might coherently interface with these (e.g. in the design of foundations or deep basement structures) there is concerted effort underway around the world to develop and implement LSD techniques for geotechnical engineering. Within Europe, EN-1997–1 (commonly referred to as Eurocode 7, or EC7) embodies LSD principles for geotechnical engineering designs (CEN, 2004; Becker & Moore, 2007).
- Europe (1.00)
- North America > United States (0.68)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type (0.69)