查看更多>>摘要：Preventing the propagation of methane or coal dust explosions through the use of active explosion-suppression systems remains one of the most underutilised explosion controls in underground coal mines. As part of the effort to develop better technologies to safeguard mines, the use of active barrier systems was investigated at Kloppersbos in South Africa. The system is designed to meet the requirements of the European Standard (EN 14591-4 2007) as well as the Mine Safety Standardisation in the Ministry of Coal Industry, Coal Industrial l Standard of the Peoples Republic of China (MT 694-1997). From the tests conducted, it can be concluded that the ExploSpot System was successful in stopping flame propagation for both methane and methane and coal dust hybrid explosions when ammonium phosphate powder was used as the suppression material. The use of this barrier will provide coal mine management with an additional explosion control close to the point of ignition and may find application within longwall faces further protecting mines against the risk of an explosion propagating throughout a mine.
查看更多>>摘要：In underground constructions, a good ventilation design not only delivers fresh air to establish good working environment, but also provides a scientific and reliable basis to prevent disasters. In emergency cases, unexpected closure of the main airways may occur, providing the workers with alternative airways is substantial. This is important not only to sustain personnel lives, but also to prevent the mine ventilation system from damage. In this research, alternate solutions were introduced in case of failure in the underground construction to keep a pre-assigned fixed quantity in a working place for mine ventilation network. Eight different collapse scenarios were proposed to study their effect on the air quantity distribution among the branches in the ventilation circuit. From these scenarios, it is found that providing a sufficient air quantity in the working places could be achieved through modification of the network topology and adjusting the values of the regulators pressure. It is also indicated that the distance between the collapse and working places has a great effect on the amount of air delivered to it. A reduction in the power consumption could be done by re-arrange the installed regulators and decreasing the number of nodes and branches inside the network. A relationship representing the effect of changing the network topology on the total network power consumption was deduced through regression analysis. It is found that the total network power is quadratic dependent on the number of regulators and number of branches while it is directly dependent on the regulator power.
查看更多>>摘要：There are many soft-rock roadway coal mines in China. The surrounding rocks of the high-stress soft-rock roadways in deep mine are especially difficult to be supported using the traditional supporting way. In this study, the south wing rail roadway on the second level of Yunjialing coal mine in China was used as an example to analyze the deformation and failure characteristics and influencing factors of roadway. On this basis, this study proposed the equalized yielding support idea which employs the yielding rings to realize the pressure equalization on the bolts and cables in the section. To achieve this purpose, the first bolt-mesh-cable equalizing pressure yielding support was integrated with the second grouting reinforcement. The results proved that the yield rings of the bolts and cables on the spandrel of the arched roadway firstly developed yielding deformation;then the deformation extended to the vault of the roadway;the bolts and cables achieved a yielding extreme value of 15 and 18 tonnes, respectively. The roadway surrounding rock tended to be stable at the 26th day after the maintenance. The equalizing pressure yielding supporting technology plays a moderate pressure-releasing and actively controlling role on the surrounding rocks in the soft-rock roadway with large deformation.
查看更多>>摘要：Coal and ore underground mining generates subsidence and deformation of the land surface. Those defor-mations may cause damage to buildings and infrastructures. The environmental impact of subsidence will not be accepted in the future by the society in many countries. Especially there, where the mining regions are densely urbanized, the acceptance of the ground deformations decreases every year. The only solution is to limit the subsidence or its impact on the infrastructure. The first is not rentable for the mining industry, the second depends on the precise subsidence prediction and good preventing management involved in the mining areas. The precision of the subsidence prediction depends strictly on the mathematical model of the deformation phenomenon and on the uncertainty of the input data. The subsidence prediction in the geological conditions of the raw materials used to be made on the basis of numerical modeling or the stochastic models. A modified solution of the stochastic model by Knothe will be presented in the paper. The author focuses on the precise description of the deposit shape and on the time dependent displacements of the rock mass. A two parameters’ time function has been introduced in the algorithm.
查看更多>>摘要：How to model the permeability evolution of rock subjected to liquid nitrogen cooling is a key issue. This paper proposes a simple but practical method to study the permeability evolution of rocks subject to liquid nitrogen cooling. FLAC with FISH function was employed to numerically model the rock behavior under cooling. The enhanced perme-ability of the volumetric strain was defined, and the permeability was directly evaluated based on element’s volumetric strain. Detailed procedures for implementing the evolution model of permeability in this paper were presented. A case study was carried out to simulate a coal bed where liquid nitrogen was injected in the bore hole. And a semi-submerged test of liquid nitrogen was performed. The method to model the permeability evolution of rocks subject to liquid nitrogen shock in this paper was proved to be right by the test results. This simulation results are discussed with the hope to provide some insight into understanding the nitrogen cooling practice.
查看更多>>摘要：This paper presented an investigation of particle collision and penetration using the discrete element method to understand the motion of particles and improve theoretical treatment in the sieving process. The process progressively was divided into looseness, stratification, collision, and penetration. Particle penetration has a direct effect on the screening performance. The penetration probability was defined, and the mathematical relationships between particle penetration and vibration parameters were established using the least squares method. To obtain the ideal penetration probability for materials the amplitude and frequency should preferably be near 3.0 mm and 25 Hz, respectively. The vibration direction angle has only a slight effect on penetration. The stage of the screening process from 0.1 to 0.7 s is the primary region for collision and penetration. This paper focused on the sieving process to more fully understand how particle collision and penetration influence the screening efficiency.
查看更多>>摘要：Pyrite has a significant effect on the spontaneous combustion of coal. The presence of pyrite can change the propensity of coal towards spontaneous combustion. The influences of various pyrite contents on the parameters of spontaneous combustion, such as index gases, temperature and released heat etc., were investigated in this study. Coal samples with different pyrite contents (0%, 3%, 5%, 7%and 9%) were made by mixing coal and pyrite. The oxidation experiments under temperature-programmed condition were carried out to test the release rate of gaseous oxidation products at different temperatures. Differential scanning calorimeter (DSC) was employed to measure the intensity of heat release during coal oxidation for various pyrite contents. The results indicate that pyrite can nonlinearly accelerate the process of spontaneous combustion. The coal sample with a pyrite content of 5% has the largest CO release rate and oxygen adsorption as well. However, the coal sample with a pyrite content of 7% has the largest rate of heat flow according to the results from the DSC tests. Pyrite contents of 5%–7% in coal has the most significant effects on spontaneous combustion within the range of this study. The conclusions are conducive to the evaluation and control for the spontaneous combustion of coal.
查看更多>>摘要：Mine refuge chambers are used to shield miners who fail to escape from the mine when incidents occur. Environment maintaining system plays a key role in stabilizing thermal environment of a mine refuge chamber against heat emitted from metabolism and transferred from outside. The safety and comfort of refugees are closely related to the environment maintaining system design. In order to improve the comfort of refugees, optimization on the environment maintaining system has been done based on the previous work. To evaluate the environment of the chamber, eight volunteers were involved into the experiment. Under close observation and safety protection, they lived in a heat-isolated test chamber for 106 hours. The volunteers were asked to maintain low level of activities to simulate refugees’ situation. It shows that the environment maintaining system worked well and the temperature, relative humidity and emitted harmful air content such as CO2 and CO were all kept in the safety level, and no discomfort was felt by volunteers at all.
Mehdi NajafiSeyed Mohammad Esmaiel JalaliReza KhaloKakaieFarrokh Forouhandeh...
318-324页
查看更多>>摘要：During underground coal gasification (UCG), whereby coal is converted to syngas in situ, a cavity is formed in the coal seam. The cavity growth rate (CGR) or the moving rate of the gasification face is affected by controllable (operation pressure, gasification time, geometry of UCG panel) and uncontrollable (coal seam properties) factors. The CGR is usually predicted by mathematical models and laboratory experiments, which are time consuming, cumbersome and expensive. In this paper, a new simple model for CGR is developed using non-linear regression analysis, based on data from 11 UCG field trials. The empirical model compares satisfactorily with Perkins model and can reliably predict CGR.
查看更多>>摘要：Security monitoring system of coal mines is indispensable to ensure the safe and efficient production of colliery. Due to the special and narrow underground field of the coal mine, the electromagnetic interference can cause a series of misstatements and false positives on the monitoring system, which will severely hamper the safe production of coal industry. In this paper, first, the frequency characteristics of the interference source on the power line are extracted when equipment runs normally. Then the finite difference time domain method is introduced to analyze the effects of the electromagnetic interference parameters on the security monitoring signal line. And the interference voltage of the two terminal sides on the single line is taken as evaluating indexes. Finally, the electromagnetic interference parameters are optimized by orthogonal experimental design based on the MATLAB simulation on the normal operation of equipment.
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