This paper discusses the application of numerical modelling techniques to the study of the factors influencing the effectiveness of support used in mining deep level tabular ore bodies characteristic of the South African gold fields. The work described forms part of an ongoing programme of research aimed at establishing a rationale for the design of stope support. Attention is focused on the development of a model that takes into account the blocky nature of the typically fractured and bedded rock in the skin of such excavations; this discontinuum model has been analysed using UDEC. The objective of this modelling is to investigate trends in support performance with variation in simple parameters such as support spacing, and support force or resistance; the use of load spreaders has also been investigated. Results are presented for one of the parameter studies, carried out under the quasi-static conditions of a normal mining procedure, and for the analysis of an example of dynamic loading representing a seismic event.
The work described in this paper forms part of an ongoing programme of research aimed at establishing a rationale for the design of stope support. This programme makes use of several approaches, numerical modelling is one of these. The modeling approach is attractive as the cost of extensive underground monitoring is prohibitive. Research has shown that the face area is where most attention to support requirements is needed to improve the safety of mine workers (Roberts and Jager 1991). Conditions in this area are influenced by many factors, however, given a set of conditions the local stability of the usually intensely fractured hanging wall is largely dependent on the detailed mechanisms of interaction between supports and the blocky rock at the skin of the excavation. Detailed modelling of this region may provide a better understanding of support-rockmass interaction. While the use of numerical modelling techniques has grown over the past decade, until recently detailed modelling of blocky systems has not been widely used. Most of the modelling work carried out has made use of continuum models, the results have provided insights into the behaviour of the rockmass surrounding stopes at a global scale but, on the whole, provide at most a crude assessment of the local stability of the hangingwalll in the face area. The discontinuum model used to investigate aspects of support rockmass interaction is briefly described. Verification of model behaviour by comparison with physical observations is needed to give credence to the results and conclusions obtained. The data available for verification is limited, typical data used to verify the model developed for this project is indicated. The required parameter studies have been carried out for static conditions and some preliminary assessment of the models behaviour under dynamic loading has also been made. Results for one of the three parameter studies are presented and some conclusions drawn. An example of the modelling of the influence of dynamic loading representing a seismic event in the stope hangingwall is also presented and discussed.
