Predicting cave initiation and propagation

Abstract The most widely used method for predicting the onset of continuous caving is Laubscher’s caving chart. A detailed examination of this method was undertaken which concluded that it had limitations which may impact on results, particularly when dealing with stronger rock masses that are outside current experience. These limitations relate to inadequate guidelines for adjustment factors to rock mass rating (RMR), concerns about the position on the chart of critical case history data, undocumented changes to the method and an inadequate number of data points to be confident of stability boundaries. A review was undertaken on the application and reliability of a numerical method of assessing cavability. The review highlighted a number of issues, which at this stage, make numerical continuum methods problematic for predicting cavability. This is in particular reference to sensitivity to input parameters that are difficult to determine accurately and mesh dependency. An extended version of the Mathews method for open stope design was developed as an alternative method of predicting the onset of continuous caving. A number of caving case histories were collected and analyzed and a caving boundary delineated statistically on the Mathews stability graph. The definition of the caving boundary was aided by the existence of a large and wide-ranging stability database from non-caving mines. A caving rate model was extrapolated from the extended Mathews stability graph but could only be partially validated due to a lack of reliable data.
Keywords: Cave initiation, Propagation, Laubscher caving chart, Numerical modelling, Mathews stability graph, Stability, Cavability.

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Summary: The current theory of how explosives fracture rock offers no explanation for the improvements in fragmentation and the reduction of fly rock and back break which occurs when an adequate inter-row delay time is used. Nor does it explain why fragmentation improves with rectangular drill patterns where the hole spacing may be as much as four times the hole burden. A new theory of rock fragmentation is proposed which builds on the existing theory. It offers rational explanations for the many...
Publication: CIM Bulletin
Author(s): P.H. Oliver
Keywords: Drill pattern, Blasting, Fragmentation, Fly rock, Back break, Inter-row delay time.
Issue: 1071
Volume: 96
Year: 2003
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Summary: The knowledge of the initial stress field is not always sufficient to ensure the stability of mining stopes due to the high-stress variations generated by mining. Monitoring of these openings is then necessary and can provide quantitative information (deformations and stress variations) as well as qualitative information (state of stability). An applied technique for following the variations of stress and deformation in static and dynamic conditions, in relation to the evaluation of the...
Publication: CIM Bulletin
Author(s): G. Ballivy, A.P. Bois, A. Ghorbal, V. Hajiabdolmajid, K. Saleh
Keywords: Stress variations, Stability, Monitoring, Deformations, Cylindre Instrumenté de l’Université de Sherbrooke (CIUS).
Issue: 1071
Volume: 96
Year: 2003
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Summary: The southwest wall of the Lornex Pit at the Highland Valley Copper mine has been experiencing slope displacements since 1978. Measures to manage the displacements on previous pushbacks have included stepping out, scheduling pushbacks to unload the crest of unstable areas, slope dewatering and mining with intensive slope monitoring. The final pushback on this wall is currently being mined and substantial modifications to the slope geometry could prove to be uneconomical. As a result, a...
Publication: CIM Bulletin
Author(s): H.W. Newcomen, L. Shwydiuk, C.S. Maggs
Keywords: Slope displacement, Pushbacks, Stability, Engineering geology, Hydrology,
Open pit.
Issue: 1071
Volume: 96
Year: 2003
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Summary: This paper focusses on new developments regarding thermal rock fragmentation applications. The technology consists of a strong burner powered by diesel fuel and air. The thermal reaction that is created allows for the enlargement of 125 mm to 450 mm holes by breaking the rock in a spalling effect. It has been used for over 30 years in Russian open pit mining. Following an agreement between Dynamitage T.C.G. Inc. and the owner of the technology, major improvements have been brought to this...
Publication: CIM Bulletin
Author(s): S. Poirier, J.-M. Fecteau, M. Laflamme, D. Brisebois
Keywords: Thermal rock fragmentation, Rock breaking, Open pit mining, Drilling, Bulk sampling, Narrow-vein extraction.
Issue: 1071
Volume: 96
Year: 2003
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Summary: Terrestrial photogrammetry has been used for many years to build three-dimensional pictures for analytical purposes. Photographs can include images from open pit mine walls, ground topography, mine buildings infrastructure or accident scenes. Analysis and co-ordinate estimation in early photogrammetric systems demanded the use of specialized and costly optical-mechanical stereocomparators. Few of these instruments could be interfaced with computers to provide databases, and all required...
Publication: CIM Bulletin
Author(s): S. Klingmann, G. Blackwell
Keywords: Digital video plotter (DVP), Digital photogrammetry, Three-dimensional analysis, Normal case geometry, Complex case geometry.
Issue: 1071
Volume: 96
Year: 2003
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