Status of Outburst Research at the University of Wollongong

There has been an ongoing research on coal and gas outburst for the past two decades at the School of Civil, Mining and Environmental Engineering, University of Wollongong. Research study began with a humble beginning, initially conducting basic laboratory studies on the coal and gas properties, progressing into the determination of gas content of coal by sorption technique and the effect of gas pressures on coal strength. The present laboratory facilities and research interests are extended to include the study of coal permeability and shrinkage properties and their effect of gas drainage characteristics with respect to gas type, and pressures. All the changes are examined with respect to changing in-site geological conditions of the coal deposit investigated. The aim is to provide a long-term support to industry in establishing a data bank for Australian coal deposit characteristics and properties. INTRODUCTION For more than two decades, there has been a continuous program of research at the School of Civil, Mining and Environmental Engineering, University of Wollongong. Much of the early research studies were carried out in collaboration with the late Dr Ripu Lama. Initially the main study was related to sorption technique for determining gravimetrically the gas content of coal, and the extended later to volumetric method. Other studies undertaken included the modelling of gas sorption in coal (Nguyen, 1988). The next phase of the research involved the development of a multi function outburst rig (MFORR) for outburst research. The MFORR was initially used to study the effect of gas environment on the strength properties of coal including: 1. The effect of gas pressure on coal tensile strength, using the well known Brazilian method of indirect tensile testing of cylindrical core samples in different gas pressure confinements. 2. The effect of gas pressure gradient on coal load bearing capacity. 3. Study of the strength of coal by examining the particle size distribution of drill cuttings under different gas environments. A high precision drill of controlled speed up to ten different levels was used to study the changes in particle size distribution with respect to increased gas type, gas pressure. The changes in coal strength properties were also compared with drilling of coal in air (Aziz, Hutton and Indraratna, 1996). Concurrent with the above, an extensive study of various coal seams gas content was conducted using an in-house built adsorption and desorption apparatus. The local coal mining companies with matching grants being provided by the University of Wollongong, though small, mostly provided financial support. Recent research emphasis has since been shifted towards the establishment of a long-term database for coal properties including coal permeability, coal shrinkage and coal petrology, for an effective outburst management. EQUIPMENT DESCRIPTION Adsorption and desorption apparatus This equipment has been the focus of outburst program research for the past two decades. Initially it was constructed to determine indirectly, and gravimetrically the gas content of coal at different gas pressures, nowadays it is also used for coal sample preconditioning, prior to permeability, coal shrinkage and coal strength tests. The apparatus (Figure 1) consists of number cylindrical pressure vessels, known as pressure ‘bombs’. Coal samples are sealed in gas bombs and pressurised to a saturation level at various predetermined pressures up to 5 MPa. The sample containers are immersed in a water bath, but are isolated from the water bath by copper sleeves to keep them dry. A thermostatically controlled water bath (with a stirrer) allows the coal samples to be kept at the desired temperatures. Further details of equipment construction, operation and gas content calculations at various pressure levels are described elsewhere (Aziz and Ming-Li, 1999).