Investigations into the effect of size and width to height ratio on the strength of the laboratory sized coal specimens
The design of bord and pillar working in South African collieries is based on the pillar strength formula developed by Salamon and Munro1967 and which has been used widely since then for designing pillars. This formula is based on the statistical analysis of 27 collapsed and 98 intact coal pillar cases from collieries located in the Transvaal and the Free state. The main objective of this study is to establish the difference in the strength of the coal material in ditferent seams by means of laboratory testing. In this manner, some 753 coal samples from 10 collieries from 4 seams were tested. The size and width to height ratio effects on strength were analysed. The size effect showed that the difference between the seams was obvious, with a difference of 59,4 per cent between the strongest and weakest coal. The statistical re-analysis showed that the strength of the six blocks from the No 2 seam, Witbank Coalfield occurred in a fairly tight strength range; and that laboratory coal strengths from individual seams or mines could deviate to a significant although relatively small extent from the overall average.
A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requir tents for the degree of Master of Science in Engineering. Johannesburg 1996.
Canbulat, Ismet (1996) Investigations into the effect of size and width to height ratio on the strength of the laboratory sized coal specimens, University of Witwatersrand, Johannesburg, <http://wiredspace.wits.ac.za/handle/10539/22074>