Rotating machinery prognostics: State of the art, challenges and opportunities

Damage initiation and propagation in hard rock during tunnelling and the influence of near-face stress rotation

The contemporary business environment has raised the strategic importance of the maintenance function in organizations which have significant investment in physical assets. Four strategic dimensions of maintenance management are identified, namely service‐delivery options, organization and work structuring, maintenance methodology and support systems. The alternatives available are reviewed: the guidelines for selection of these alternatives, the key decision areas in each of the four dimensions, as well as the critical success factors for the transformation process are discussed. The two factors that permeate in these strategic dimensions are human factors and information flow; the latter can be made more efficient by embracing the e‐maintenance model.

Strategic dimensions of maintenance management

Spalling and strain bursting has long been recognized as a mechanism of failure in deep underground mines in hard rock and in deep infrastructure tunnels. The latter is a significant growth industry, particularly in Europe where subalpine base tunnels in excess of 10 m wide and dozens of kilometres long are being driven by tunnel boring machine (TBM) through alpine terrain at depths greater than 2 km. In more massive granitoid or gneissic ground, these tunnels have experienced significant spalling damage. En route to a practical predictive technique for this condition, the author utilizes a number of analytical and micromechanical tools to validate a simple empirical predictive model for tunnel spall initiation. The true nature of damage and of yield, as the result of extensile damage accumulation, in hard rocks is examined using these tools. Based on the resultant conceptual model, the author expands on the empirical damage threshold, using a spalling limit to differentiate stress paths that lead to crac...

The 2003 Canadian Geotechnical Colloquium: Mechanistic interpretation and practical application of damage and spalling prediction criteria for deep tunnelling

The oldest and most common maintenance and repair strategy is “fix it when it breaks”. The appeal of this approach is that no analysis or planning is required. The problems with this approach include the occurrence of unscheduled downtime at times that may be inconvenient, perhaps preventing accomplishment of committed production schedules. Unscheduled downtime has more serious consequences in applications such as aircraft engines. These problems provide motivation to perform maintenance and repair before the problem arises. The simplest approach is to perform maintenance and repair at pre-established intervals, defined in terms of elapsed or operating hours. This strategy can provide relatively high equipment reliability, but it tends to do so at excessive cost (higher scheduled downtimes). A further problem with time-based approaches is that failures are assumed to occur at specific intervals.

A. K. S. Jardine

Papers

Maintenance, Replacement, and Reliability