Journal of The South African Institute of Mining and Metallurgy 

About: Journal of The South African Institute of Mining and Metallurgy is an academic journal published by Academy of Science of South Africa. The journal publishes majorly in the area(s): Coal & Coal mining. It has an ISSN identifier of 0038-223X. It is also open access. Over the lifetime, 2445 publications have been published receiving 26480 citations. The journal is also known as: Journal of the Southern African Institute of Mining and Metallurgy & SAIMM.

A statistical approach to some basic mine valuation problems on the Witwatersrand

Abstract: Certain fundamental concepts in the application of statistics to mine valuation on the Witwatersrand are discussed, and general conclusions are drawn regarding the application of the lognormal curve to the frequency distribution of gold values An indication is given of the reliability of present valuation methods on the Rand It is shown that the existing over- and under-valuation of blocks of ore listed as high-grade and low-grade, respectively, can be explained statistically Suggestions are made for the elimination of such errors and for the improvement of the general standard of mine valuation by the use of statistical theory

A study of the strength of coal pillars

Abstract: A formula, which defines approximately the strength of coal pillars in South African collieries, is derived. The derivation is essentially empirical, based on data obtained from a survey of actual mining dimensions. The data include information concerning both stable and collapsed areas of mining. It is argued that the ratios of the predicted strengths to the calculated loads at failure, that is, the critical safety factors, form a frequency distribution. This distribution is centered around the safety factor of unity. The probability that a pillar will be stable is indicated by the ordinates of the cumulative distribution curve. This study assumes that the logarithm of the critical safety factor is normally distributed. It is postulated that the strength of pillars can be expressed, in the given range of dimensions, as a power function of the height and the width. The values of the three unknown parameters in this function, the constant multiplier and the powers of width and height, are estimated by the method of maximum likelihood. This method also gives an estimate of the logarithmic standard deviation of the distribution. The derived strength formula descriptionbes satisfactorily the information obtained from the survey of mining dimensions. The comparison of the derived results with those available in the literature shows no significant difference concerning the effect of pillar width. However, the influence of pillar height is found to be less than is estimated by previous authors.

Estimating the strength of rock materials

Abstract: A practical approach for estimating the strength behaviour of rock materials is presented. The demand for data on rock properties in engineering design is considered, and it is shown that, based on the trends observed in the South African mining industry during the last twenty years, simple and easy-to-use methods for the estimation of the uniaxial and triaxial strength of rock materials are needed. It is shown that the uniaxial compressive strength of rock can be conveniently determined from the point-load strength index, which is obtained underground on unprepared rock cores. The triaxial strength of rock can be estimated for most practical purposes from empirical strength criteria. Two such criteria are proposed that allow estimation of the triaxial strength for rock materials to about 10 per cent. The only input required for these criteria is the uniaxial compressive strength. The validity of the practical approach outlined in this paper is confirmed from the experimental tests conducted on some 700 rock specimens representing five rock types. A practical example for the prediction of rock strength is given.

A geomechanics classification system for the rating of rock mass in mine design

Abstract: The mining rock-mass rating (MAMA) classification system was introduced in 1974 as a development of the CSIA geomechanics classification system to cater for diverse mining situations. The fundamental difference was the recognition that in situ rock-mass ratings (AMA) had to be adjusted according to the mining environment so that the final ratings (MAMA) could be used for mine design. The adjustment parameters are weathering, mining-induced stresses, joint orientation, and blasting effects. It is also possible to use the ratings (AMA) in the determination of empirical rock-mass strength (AMS) and then in the application of the adjustments to arrive at a design rock-mass strength (DAMS). This classification system is versatile, and the rock-mass rating (AMA), the mining rock-mass rating (MAMA), and the design rock-mass strength (DAMS) provide good guidelines for the purposes of mine design. However, in some cases a more detailed investigation may be required, in which case greater attention is paid to specific parameters of the system. Narrow and weak geological features that are continuous within and beyond the stope or pillar must be identified and rated separately. The paper descriptionbes the procedure required to arrive at the ratings, and presents practical examples of the application of the system to mine design,