Thesis (Ph. D.)--Middle East Technical University, 2004. / Keywords: Accident Report Form, Accident Database, Occupational Diseases and Mine Accidents, Accident Reporting System, Health and Safety Management Tool.

The methane diffusion coefficient in coal matrix is one of the basic parameters required in simulation of gas transport in coalbeds. Its value has been assumed to be constant throughout the production life of a coalbed methane reservoir. The adequacy of this assumption, however, needs to be examined. The objective of this study is to conduct an experimental investigation in order to measure the micropore diffusion coefficient and examine its dependency on reservoir pressure, desorption of methane, and water saturation. The techniques used in previous studies are either inadequate or incapable of serving for this purpose. This investigation introduces the transient interflow method to measure D. A modeling equation is derived based on Fick's Law and solved using the experimental results to obtain the value of D. The numerical solution evidently show that the diffusion coefficient is methane concentration, pressure and water saturation dependent. A continuous decrease in the value of D with decreasing methane concentration in coal is observed, and related to the changes of dominant flow mechanism in coal matrix and the shrinkage of coal matrix induced by desorption of methane. Results of the experiments conducted at different pressures indicate that the release of methane from coal at late time diffusion is much slower at a lower pressure. This may partly be attributable to the higher degree of coal matrix shrinkage at low pressures. The methane diffusion in coal matrix, therefore, should not be described by a unipore model or a single diffusion coefficient model. The experiment with a wet sample shows that the value of D is a strong function of water content in coal. The decrease in the value of D due to the presence of water in coal also changes with mean concentration of methane in coal. The diffusion coefficient measured for a water content 0.53% may be 30 times smaller than for the dry sample at late time diffusion.

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At the present time our understanding of rock behaviour under mining conditions is largely empirical. Limitations in this approach have been recognized and laboratory testing is gradually being introduced as another source of information. An adequate correlation of laboratory test results with field conditions has not been established but test results are being published, as in the report on mining practices at Elliot Lake (1)*, on the basis of their comparative value. This study aims at establishing some of the physical properties of an andesite rock by conducting tests on specimens cut from diamond drill core. The results may be useful for comparison with other rock types and for relating laboratory test results to rock behaviour under mining conditions.

The scientific principle considered in this thesis is the relation at the surface of the earth, of the amplitude, phase and frequency of orthogonal components of the naturally occurring electric and magnetic field fluctuation to the resistivity profile of the subsurface geology. A method of resistivity profiling, known as magnetotellurics, was presented in a paper by Cagniard, (1953) and extended in later papers by Wait, (1954) Tikhonov and Shakhsuvarov (1956), Cantwell and Madden (1960), Smith, Provazek and Bostick, (1961), Price, (1962), Vozoff, Hasegawa and Ellis (1963) and others. Results obtained by these researchers have shown that the basic theory of magnetotelluric methods require some modification for extension beyond very simple geologic situations.

Missing pages. / This thesis is in the area of engineering theory. It is concerned with the combining of existing scientific theories into a rational hypothesis for predicting the loading of pillars. Hitherto, this has only been possible in a very crude way and only for horizontal workings. Analytical work to predict pillar loadings for long mining zones in elastic ground produces equations which include, in the form of dimensionless parameters, the significant geometrical and material-properties affecting pillar loading. Additional analytical work demonstrates that various arching and plastic theories are unlikely to be of any use in this problem. [...]