1,721,051 research outputs found
Improving emergency management in underground coal mines
No full textThe findings of ACARP funded research project C17008 - Optimising the collection of information for effective use in the event of an emergency at an underground coal mine is reported. The aim of this ACARP funded research project was to identify ways of optimising the information collection and reporting processes used in emergencies in underground coal mines to ensure rapid and effective response, minimising the risk to life. This was to be achieved through evaluating the current emergency management systems at mines, identifying good practice and also areas that needed improvement. There were three areas of focus for the project: the control room, senior mine official on site and the incident management area. The control room in particular is a key area where accurate information is required during an incident especially in the early stages until a senior mine official can take charge. The control room remains the first point of contact during an incident for most personnel. Speedy evacuation and in seam response is predicated upon knowing what is happening and where everyone is located. A number of mines in NSW and Queensland were visited and their emergency management systems were analysed. In Queensland this was undertaken as part of the involvement in the level one emergency response exercises (LOERS)
Underground Coal Operators' Conference
No full textLongwall mining is a major mining method to extract thick, flat-lying and extensive seams. Due to the nature of this mining method, the overlying strata move continuously downwards into goaf and as a result, surrounding rocks are distressed, deformed and fractured. In the near area above the mined coal seam, both vertical and horizontal fracturing networks are evident, however within the higher zones, bed separation and slippage are the dominant displacements. The enhanced cracks alter hydraulic characteristics (porosity and permeability) of the rock mass, consequently disturbing the groundwater and surface water flow regime. There have been various techniques utilised to study mining-induced fracturing mechanisms and changes in water flow systems. They mainly include empirical, physical, analytical and numerical approaches. Of note is that due to the complexity of the issue and difficulties in the implementation of costly and time-consuming in-situ measurements, currently, numerical simulation is a popular approach. The aim of this review paper is to present the current state of the art in mining-induced goaf overburden fracturing and its interaction with groundwater and surface water
Underground Coal Operators' Conference
No full textThe load transfer mechanisms of cable bolts differ from normal rebar bolts. Cable bolts used in mines are basically steel strands with different constructions depending on the number of wires or elements and the way that these elements are laid. Tendon bolts (rebar and cable) are normally
evaluated for strength and load transfer properties. The strength of tendon can be carried out by tensile
failure tests, while the load transfer strength is evaluated by pull and shear strength tests. Short
Encapsulation Pull Testing (SEPT) is used to study of the load transfer capacities of tendons, and can
be undertaken both in the laboratory and in situ. A new apparatus known as Minova Axially Split
Embedment Apparatus (MASEA) was used to study load-displacement characteristics of smooth versus
spiral profile cable bolts. Minova Stratabinder grout was used for encapsulating 400 mm long 19 wire 22
mm diameter superstrand cable in the embedment units. The anchorage of the cable on two sides of the
embedment apparatus were intentionally installed at different lengths, to allow the cable to be pulled out
from one side of the anchorage. The spiral wire strand cable bolts achieved higher peak pull-out load at
minimum displacement in comparison with smooth surface wire strand. The peak pull out force increased with the age of encapsulation grout. The MASEA was easier to assemble and test at a short period of time, thus allowing quick and repeated tests to be undertaken
Underground Coal Operators' Conference
No full textUnderground support system using tendons has been one of the significant achievements in Civil and Mining engineering endeavours in facing challenges of ground control. However, shear failure of rock bolts is still one of the least monitored phenonmenon in underground excavations with respect to seismic events. The understanding of the performance of rock bolts under dynamic loading condition requires a great deal of research. A series of tests were undertaken utilising a drop hammer mass of 600 Kg from a maximum height of 3.7 m over concrete blocks in the double shear box with chemical resin encapsulated a rock bolt to investigate the performance of rock bolts under dynamic shear load. Load cells, displacement laser and high speed camera were used to monitor the test. Results from the data analyses are presented in the form of displacement, hammer mass drop velocity, acceleration and force variation with time for all components involved in each test. The time factor was found to contribute 30 % of the shear load in static testing in comparison with dynamic; In particular, the force-displacement curve and energy absorption for the reinforcement system are presented to examine the performance of rock bolts and conclusion drawn
Underground Coal Operators' Conference
No full textThe shear strength property of artificial rock joints with triangular and sinusoidal roughness was investigated in the laboratory by the aid of direct shear test machine. In particular, this paper includes literature review of past studies on shear strength properties of unfilled and infilled rock joints, experimental studies on shear strength properties of artificial rock joints with triangular, sinusoidal and plain roughness under various normal load and comparison between shear behaviour of these rock joints having different roughness patterns. This research presents the concepts development essential to envision the shear behaviour of rock slopes aided by artificial rock joints. It was concluded that the shear behaviour of rock joints is a function of normal stress, roughness value and pattern of asperity
Underground Coal Operators' Conference
No full textPast studies on mechanical properties of grout were critically investigated and classified. Small scale and large scale samples were cast using cube and cylindrical moulds. Samples were left undisturbed to cure for various time intervals ranging from 1 to 21 days. Effects of sample scaling on the Uniaxial Compressive Strength (UCS) of Minova Stratabinder HS were studied, using a universal compression testing machine. In addition, rectangular samples were cast to investigate bending resistance of the grout product. Four point bending test was carried out on the samples with curing time ranging from 1 to 21 days. It was found that compression resistance of the grout increased with respect to curing time and initial studies on flexural strength showed that the bending resistance of grout reduced with prolonged curing times
Mine subsidence predictions using a mechanistic modelling approach
No full textA practical, predictive method, based on closed form solutions for displacement and strain around longwall panels, is proposed to facilitate the assessment of subsidence and changes to ground conditions above longwall mining. The displacement discontinuity method is employed to simulate the displacement and strain field around a single longwall panel in a three-dimensional transversely isotropic medium. The analytical solutions are effectively combined and implemented in MATLAB language, which allows for deriving key information to subsidence predictions. Predictive accuracy, applicability and efficiency of the code are demonstrated using data from collieries in New South Wales. Close agreement was achieved between the key parameters maximum tensile strain, maximum tilt, maximum convex and minimum concave curvature derived by empirical methods, the proposed displacement discontinuity method and survey records. However, there is still scope for improvements in this approach and additional testing is recommended in order to further validate the proposed method and evaluate its potential for practical longwall mining impact and risk assessments
The effectiveness of rapid stone dust compliance testing in underground coal
No full textThe addition of stone (limestone) dust to roadway dust in an underground coal mine increases the Total Incombustible Content (TIC) to reduce the potential of the coal dust igniting and propagating an explosion. Coal dust explosions have been proven to be one of the most severe hazards in an underground coal mine hence as Queensland legislation requires the use of roadway stone dusting, the required levels of TIC are higher than other mining districts around the world which also employ other coal dust explosion barriers. Compliance testing currently involves Low Temperature Ashing (LTA) of representative samples with a turn around on results of up to two weeks. To minimise the time that the mine is potentially out of compliance and unsafe, the Coal Dust Explosibility Meter (CDEM) has been tested at a Queensland underground coal mine to determine its effectiveness, through 11 different calibration methods, in rapidly measuring the TIC of roadway dust samples. The key focus of the calibration methods was to explore the effectiveness of the CDEM at its designed threshold of 80% TIC, the use of an inbuilt methane content adjustment to replicate the Queensland legislative requirement of 85% TIC and the use of actual 85% TIC calibration samples. These calibration methods were replicated using both the manufacturer provided Pittsburgh coal dust and mine site specific coal dust for calibrating the CDEM. This paper provides the results of this investigation
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