Year

1996

Degree Name

Master of Engineering (Hons.)

Department

Department of Civil and Mining Engineering

Abstract

Coal and gas outbursts are each one of the feared hazards of underground coal mining operations, and still contribute greatly to underground fatalities world wide. The nature of outbursts and their severity are dependent on several factors. The increased depth of mining, type and rank of coal, coal permeability and porosity, seam thickness, mining height and rate of mining are some of the widely acknowledged factors. The incidence of outbursts is on the increase because of increase in rate of mining and mining in deeper seams. The exact mechanism of outburst is still a subject which is occupying the minds of researchers and mine operators. This thesis is concerned primarily with the examination of the effect of sorbed gas pressure on the strength of coal. Coal strength changes have been associated with the phenomenon of coal outburst for some time and a number of researchers have made varying observations of the effect of gas pressures on coal strength. The thesis examines the changes of coal strength as a result of the changes in the sorbed gas pressures. A specially developed precision drill, developed at the Department of Civil and Mining Engineering, University of Wollongong, was utilised to permit drilling of coal samples under both normal atmospheric pressure and under confined gas pressures. The drill cuttings were used for the assessment of the changes in the particle size distribution analysis using a laser controlled high precision particle size analyser. The study included the influence of increased gas pressures on the maceral composition of coal. Gases used in the laboratory tests included CH4, CO2 and CH4 /CO2 mixture. Tests were carried out on coal samples obtained from a number of mines in the Bulli seam from the Southern Coalfield of NSW and the determination of the gas content of the coal for different gases using the gravimetric Sorption/Desorption method.

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.