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

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

Parameters affecting mine gas drainage and outburst control research

Removing gases form mine environment represents the most important challenge that any mine operator is faced with. The ease with which the challenge is met and addressed depends on better understanding of the various parameters. Coal permeability and porosity is one of the key factors affecting the drainability of the coal. Coal matrix structure and coal mineralization provide a key to various issues related to effective drainage. Abnormal geological intrusions such as faults and dykes are likely to adversely affect the drainability of the coal seam. A combination of coal permeability, volumetric matrix change and petrography studies has been found to provide a new methodology in determining the ease with which a coal seam can be drained particularly with respect to geologically difficult sites. Various methodologies and techniques are described to provide the latest of research currently been pursued at the University of Wollongong, NSW, Australia, which is now providing a clear direction to predicting the drain ability of gassy coal seams

Reducing coal mine GHG emissions through effective gas drainage and utilisation

Gas emission from Australian coal mining is estimated to account for 4-5% of the nation’s 559 million tonnes of CO2 equivalent (MtCO2-e) Greenhouse Gas (GHG) emissions. With the intense focus on global GHG management and reduction, to slow the rate of climate change, significant community and political pressure exists to reduce the rate of gas emission. In December 2007 Australia committed to join the Kyoto Protocol, which in part requires annual GHG emissions not to exceed 108% of 1990 levels by the end of the 2012 commitment period. The current Australian Federal Government is presently developing the Australian carbon pollution reduction scheme, which is due to be implemented by 2010. This scheme is expected to place a value on GHG emissions and thereby introduce a financial penalty/incentive on organisations to manage and reduce their GHG footprint. In the case of the Australian coal industry, with an estimated annual GHG contribution of 22.5 Mt CO2-e, the introduction of the emissions reduction scheme will add in the order of half a billion dollars to the cost of operations (based on a carbon unit cost of $20/t CO2-e). In light of such a significant additional cost it can be expected that gas capture and emissions reduction will receive an unprecedented increase in attention and corporate support. This paper discusses the various sources of gas emission from underground coal mines and describes methods to improve both the capture and utilisation of this gas to reduce GHG emissions

Experimental and numerical methodology assessment of load transfer capacity of bolts

In Australia, the common method of laboratory testing of bolt for load transfer capacity determination is by short encapsulation push testing. Some concerns are raised about the validity of the test methodology, as the method does not reflect on the actual load transfer characteristics of bolt in real field situation. Thus, laboratory testes were carried out to examine the load transfer mechanisms of bolts in both the push and pull conditions. Tests were conducted by shearing a short resin encapsulated bolt out of a cylindrical steel sleeve. Three types of bolts with different surface profile configurations were tested. The study was complemented with numerical simulation of the test methods. Irrespective of bolt type the average shear load and shear stress values were found to be greater in push test, and the displacement at peak shear load was greater in pull test. The average shear stiffuess values were greater in push test. The numerical simulation of the bolts provided a clear understanding of the stresses and strains generated by different bolt profiles during both the pull and pull testing process, thus allowing a better appreciation of the load transfer mechanism process

Experimental and numerical study of double shearing of bolt under confinement

The shear behaviour of reinforced rock joints is investigated for the bolt-grout-rock interaction and for failure mechanism. The effectiveness of the bolt application under lateral and axial loading conditions within surrounding materials is investigated in different medium strength. Double shearing testing of bolts were studied in concrete blocks of 20, 40, 50 and 100 MPa strengths, subjected to different pretension loads of 0, 5, 10, 20, 50 and 80 KN respectively. The experimental study was complemented with three-dimensional numerical analysis. Parameters examined include: shear resistance, shear displacement, induced strains and stresses during bolt bending process and its ultimate failure across the sheared joint planes. The conclusions drawn from the study were; the level of bolt resistance to shearing was influenced by the bolt profile configuration, the strength of the rock or medium influenced the level of load generated on the bolt, and the increase in bolt pretension has contributed to the increased shearing load of the bolted medium

Shear testing of 28 mm hollow strand TG cable bolt

Cable bolts were introduced to the coal mining industry in the early 1980’s mainly for roadway reinforcement as a secondary means of support. Their application is dictated by the nature of the stratification, ground stress conditions and the size of the opening. Double shearing tests were carried out on the 28 mm hollow strand Jennmar “TG” cable bolt, two tests were conducted to evaluate the shearing characteristics of the bolt and to gain a better understanding of the shearing behaviour of the cable. The first test was limited by a 50 mm travel on the testing machine and produced a shear load of 900 kN (92 t) at the maximum 50 mm displacement, with axial load generated on the cable bolt reaching 238 kN (24.3 t). In the second test the machine travel was increased to 75 mm, cable failure due to shear loading was achieved at 1 354 kN (138 t) load and a vertical displacement of 59 mm, with cable axial load in the order of 385 kN (39.3 t). Analysis of the failure mode and loads achieved indicate that the cable strands bent and the concrete crushed along the shear plane, the shear loading across the concrete and grouted cable then reached the tensile strength of the steel wires

Actions to improve coal seam gas drainage performance

Coal seam gas drainage is affected by many factors which may be generally divided into two groups, geological factors and operational factors. Studies conducted in the Bulli seam found geological factors had a dominant impact on coal seam gas drainage while operational factors had a secondary impact, affecting the amount of optimum gas drainage performance achieved within the limitations imposed by the prevailing geological conditions. Various operational factors, which are controllable by the mine operator and which have a significant impact on gas drainage effectiveness, are presented and recommendations made to improve and optimise gas drainage performance

Dust controls and monitoring practices on Australian longwalls

Fugitive dust on longwalls has always been an issue of concern for production, safety and the health of workers in the underground coal mining industry globally. Longwall personnel can be exposed to harmful dust from multiple dust generation sources. With the increase in production created from the advancement in longwall equipment, dust loads have also increased and this has resulted in an increase in exposure levels to personnel. Control processes in place for the mitigation of dust vary from mine to mine, with each individual mine having a dust mitigation setup that is only effective for that particular mine operation. While the focus in the past has quite correctly been on improving the controls on dust exposure, the future lies in identifying the efficiency of installed controls on operating longwalls, evaluating them through robust and quantitative sampling methods to ensure the most effective controls are in place to prevent occupational disease from occurring. This paper will examine the current controls for dust mitigation on longwalls and propose a new testing methodology to determine dust mitigation efficiency (DME) of installed controls for both respirable and inhalable dust. The main objective of this proposed sampling method is to identify dust loads at independent sources of dust generation in mg/tonne produced on longwall faces and quantify the efficiency of installed controls for the mitigation of produced dust on longwall faces

Bolt surface configurations and load transfer mechanism

A series of laboratory based push and pull tests were carried out to investigate how surface profile influence the load transfer mechanism of bolt/resin interface. Tests were carried out in both 75 mm and 150 mm long steel sleeves. Three types of bolts were examined, they were bolts most commonly used for strata reinforcements in underground coal mines in Australia. The bolts had near equal core diameter but of different profile configurations. The change in the length of the encapsulation sleeve was examined in light of the small number of profiles encapsulated effectively in short 75 mm long sleeves. The results showed that peak loads and displacements were directly related to the height and the spacing of the bolt surface profiles. Profile spacing appears to have greater influence on load transfer capacity than the profile height