Improving Ground Support Design by Historical Ground Fall Analysis

CIM Vancouver 2002
Gary Allen,
Abstract One of the most important rules that rock mechanics engineers are playing is to provide adequate ground support design to ensure that a safe working environment is always provided for the men working underground. Any unexpected falls of ground due to the lack of ground support are unacceptable while over support is also not acceptable from an economic point of view, especially at current low metal price.

Although ground support design can be undertaken by using numerical modeling, empirical models are still the common tools being used. These empirical models must be developed and derived from local past experiences although some global models are being extensively used in the Canadian mining industry, such as the Stability Graph, etc. To review the adequacy of the ground support practices and procedures at HBM&S, a database of case histories of falls of ground was developed and it contained more than 50 cases. In each failure, the recorded data included: location, rock type, rock mass conditions, opening and failure geometry, installed ground support and identified failure mechanism. An analysis of the ground falls in the database has been carried out in order to obtain a better understanding of their frequency of occurrences, their association with certain rock types, stope geometry and installed ground support, and to assess what changes should be made. Based on the findings from the database, the paper describes the details of changes that have been made to both support practices and mining practices in the last 5 years at HBM&S. The formation of ground support standards and changes made have been demonstrated to be successful in reducing falls of ground and providing more economical ground support system than previously used. Some projects involving innovations on ground support at HBM&S are also discussed in the paper, which include using short cable bolts as primary support at the large intersections in the development areas.
Keywords: Falls of ground, Case histories, Ground control, H.B.M&S, Empirical models, Innovations on ground support, Ground support design, Rock mechanics
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