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Wang Y.M.,China University of Mining and Technology | Wang W.Z.,China University of Mining and Technology | Shao Z.L.,Key Laboratory of Gas and Fire Control for Coal Mines | Wang D.M.,State Key Laboratory of Coal Resources and Safe Mining | Shi G.Q.,China University of Mining and Technology
Bulgarian Chemical Communications | Year: 2014

Due to great impacts to air pollution caused by residual coal oxidation in underground mine gob, monitoring and forecasting of hazardous gases emissions have become important topics in mining engineering and environmental research today. This paper presents a robot monitoring system for carbon monoxide emission from coal oxidation in spontaneous combustion condition. According to the terahertz-wave absorption spectrum, the CO concentrations are measured by using terahertz time-domain spectroscopy (THz-TDS) technique. Based on the measured values, an innovative method of CO concentration prediction has been developed by using least square support vector machine (LSSVM) with a novel hyper-parameter selection. The hourly CO concentrations have been predicted using the SVM and the hybrid LSSVM models respectively. Results show that the hybrid LSSVM has better accuracy. Statistic estimators have been employed to compare performances of the models. It has been concluded that the errors decrease and coefficients of determination increase for hybrid LSSVM model, hence it has definite practice significance and application value. © 2014 Bulgarian Academy of Sciences, Union of Chemists in Bulgaria.


Qin B.T.,Key Laboratory of Gas and Fire Control for Coal Mines | Qin B.T.,China University of Mining and Technology | Lu Y.,Key Laboratory of Gas and Fire Control for Coal Mines | Lu Y.,China University of Mining and Technology
International Journal of Mining Science and Technology | Year: 2013

In order to efficiently seal air leakages and control spontaneous combustion of coal, solidified foam was developed by adding a certain compound additive to fly coal ash and cement as the main materials. It was prepared basing on the foaming characteristic through physical and mechanical system. We studied the effects of the different types of foaming agents, the mass ratio of cement to fly ash, and the mass ratio of solid to water and content of cellulose on the performance of solidified foam. The results show that when adding the composite protein, surfactant and cellulose foaming agents. The cement-fly ash ratio of 0.75:1, the water solid ratio as large as 2:1, and the solidified foam with high properties and density of only 516 kg/m3 and compressive strength of up to 12.68 MPa were prepared. But the initial setting time, identity and compressive strength may be changed by varying the water solid ratio and/or the additives. We theoretically analyzed the influence mechanism of foam density, compressive strength and water solid ratio. The solidified foam is especially suitable for sealing surface leakage channels and filling the goaf with a wide application prospects. © 2013 Published by Elsevier B.V. on behalf of China University of Mining & Technology.


Chen P.,China University of Mining and Technology | Chen P.,Key Laboratory of Gas and Fire Control for Coal Mines | Wang E.-Y.,China University of Mining and Technology | Wang E.-Y.,Key Laboratory of Gas and Fire Control for Coal Mines | And 2 more authors.
Meitan Xuebao/Journal of the China Coal Society | Year: 2013

The real-time testing system of resistivity variation regularities of loading coal was established where resistivity variation characteristics of different kinds of coal in different orientations under different loading methods were tested. Besides, resistivity variation mechanism was expounded. The research results indicate that there lies difference in resistivity changing tendency of different coal samples along with pressure's change in the initial stage of loading. Yet, resistivity shows rising trend without exception after coal fracturing occurs. In view of the same coal sample, the changing tendency of resistivity is in consistent with that of pressure. Under different loading methods, resistivity is in fine parallelism with stress. Furthermore, coal resistivity presents apparent anisotropic characteristics. In the loading process, resistivity in different orientations shows different variation regularities. Meanwhile, the conduction characteristics of coal and evolution of pore structure codetermine the variation characteristics of resistivity.


Lu Y.,China University of Mining and Technology | Qin B.,China University of Mining and Technology | Qin B.,Key Laboratory of Gas and Fire Control for Coal Mines | Jia Y.,China University of Mining and Technology | And 2 more authors.
Advances in Cement Research | Year: 2015

Thermal insulation and setting properties are considered to be two significant parameters when inorganic solidified foam (ISF) is applied to control and extinguish coal fires. Based on studies concerning the thermal properties of porous media and experimental research on the relationship between porosity and the addition of aqueous foam, an equation describing the change in thermal conductivity with aqueous foam volume is deduced and then amended. Microscopic analysis of the process of setting is conducted by scanning electron microscopy. The results show that the coagulation of a single bubble wall and bubbles connecting with each other lead the ISF to lose fluidity gradually. A loss of fluidity time (LFT) index is then proposed on the basis of field process requirements and the aforementioned microscopic analysis, and a home-made instrument to test LFT is developed. Effects of aqueous foam volume and accelerator type, along with its addition quantity, on the LFT of ISF are investigated. The relationship equation provides a theoretical foundation for steerable adjustment of the LFT. Furthermore, under the restriction of cost, thermal conductivity threshold and LFT, the parameters of the feasible construction state areas of four different accelerators were compared; in this study AC3 was found to be the most appropriate accelerator.


Cheng J.-J.,China University of Mining and Technology | Cheng J.-J.,Australian National University | Zhou F.-B.,China University of Mining and Technology | Zhou F.-B.,Key Laboratory of Gas and Fire Control for Coal Mines
Journal of Thermal Analysis and Calorimetry | Year: 2016

To improve the flame-retardant properties of polymer materials, an organic–inorganic hybrid material was obtained by various mixed ratios of sodium silicate solution and polyisocyanate. The chemical structure of materials was characterized by Fourier transform infrared spectroscopy, and the microstructures were observed by scanning electron microscope. The influence of various ratios of polyisocyanate and sodium silicate on the flame-retardant properties of hybrid materials was emphatically investigated. The results showed that Si–O and Si–O–Si bonds were introduced into the hybrid materials and the surfaces were rougher than that of rigid polyurethane. The hybrid materials had better flame-retardant properties than the rigid polyurethane with an obvious decrease in heat release rate, spread rate of fire, decomposition rate and increase in residue and LOI value. When the hybrid materials were burning, less carbon dioxide and carbon monoxide were produced. In addition, the TG curve showed that the mass of hybrid materials decreased more slowly than the mass of the rigid polyurethane. So the hybrid materials showed excellent flame-retardant properties. © 2016, Akadémiai Kiadó, Budapest, Hungary.


Cheng J.-J.,China University of Mining and Technology | Cheng J.-J.,Australian National University | Zhou F.-B.,China University of Mining and Technology | Zhou F.-B.,Key Laboratory of Gas and Fire Control for Coal Mines
Journal of Thermal Analysis and Calorimetry | Year: 2016

Influence of expandable graphite on flame retardancy and mechanical properties of organic–inorganic hybrid material based on sodium silicate and polyisocyanate has been investigated. The results of mechanical measurement show that adding expandable graphite decreases the maximum of the compressive strength from 5.98 to 1.49 MPa. The thermal property is evaluated by thermal conductivity test, thermogravimetric analysis. The results indicate that adding the expandable graphite increases thermal conductivity of composite and lowers maximum heat release rate. The material with expandable graphite has better flame retardancy than original material with an obvious decrease in heat release rate, fire spread and thermal decomposition rate. What is more, intumescent graphite has the obvious effect to suppress flame and prevent the composite from fire. Scanning electron microscope shows that many large particles and gaps appear after compression deformation. © 2016 Akadémiai Kiadó, Budapest, Hungary


Zhou F.,Key Laboratory of Gas and Fire Control for Coal Mines | Zhou F.,China University of Mining and Technology | Sun Y.,Henan Polytechnic University | Li H.,China University of Mining and Technology | Yu G.,Coal Mine Gas Control National Engineering Research Center
Zhongguo Kuangye Daxue Xuebao/Journal of China University of Mining and Technology | Year: 2016

Low gas drainage concentration was caused by the leak in the borehole and the leakage fracture around the borehole. Based on the multi-physics field coupling theory, the mathematical model considering the leak in the borehole and the leakage fracture around the borehole was established for analyzing borehole leakage mechanism. The model was solved by COMSOL Multiphysics software. The results show that the bigger the width of the leakage fracture in the mining area is, the faster the decay rate of the gas drainage concentration is. The leakage fracture characteristic is an important factor to influence the concentration of gas drainage. In order to ensure sealing quality and improve the gas drainage results, the modern hole sealing technology not only needs to achieve the sealing in the borehole, but also seal the the leakage fracture field of coal mass around the borehole. Accordingly, two new fracture sealing technologies, namely bag-type grouting hole sealing and secondary hole sealing, were introduced emphatically in this paper with their application effects. © 2016, China University of Mining and Technology. All right reserved.


Zhou F.-B.,Key Laboratory of Gas and Fire Control for Coal Mines | Zhou F.-B.,China University of Mining and Technology | Wang X.-X.,China University of Mining and Technology | Liu Y.-K.,Key Laboratory of Gas and Fire Control for Coal Mines | Liu Y.-K.,China University of Mining and Technology
Natural Hazards | Year: 2014

Gas drainage not only ensures safety in coal mine but also produces clean energy and reduces emission of greenhouse gases. However, a good method to evaluate the efficiency of gas drainage is still absent. In this study, we firstly propose a definition of gas drainage efficiency which is defined as the ratio of the real output–input efficiency to the ideal output–input efficiency. The definition combines both engineering parameters such as radius, length of borehole and economical parameters such as drilling cost to develop a comprehensive index for the assessment of the engineering–economical efficiency. Then, three important factors to determine gas drainage efficiency including the difficulty level, the input and output, namely investment and production, and the attenuation characteristic of gas drainage are discussed. Based on the relative standards, the index can reasonably evaluate gas drainage projects with different difficulty levels, thereby avoiding dependence on an absolute standard for the evaluation of overall difficulty levels. The indicator can also take both input and output into consideration and reflect the reduction of gas drainage flow with time. Besides, we investigate the relationship between gas drainage efficiency and several engineering parameters, including borehole radius, borehole length and the quality of borehole sealing. The results show the possibility of optimizing engineering parameters to maximize gas drainage efficiency. Finally, the evaluation method is proven efficient by performing case studies. © 2014, Springer Science+Business Media Dordrecht.


Cheng J.-J.,China University of Mining and Technology | Shi B.-B.,China University of Mining and Technology | Zhou F.-B.,China University of Mining and Technology | Zhou F.-B.,Key Laboratory of Gas and Fire Control for Coal Mines | Chen X.-Y.,China University of Mining and Technology
Journal of Applied Polymer Science | Year: 2014

Rigid polyurethane foam (RPUF) composites filled with expandable graphite (EG), hollow glass microspheres (HGM), and glass fibers (GF) have been synthesized and characterized by limiting oxygen index, radiation ignition, compressing and torsion testing, and scanning electron microscopy. The results indicate HGM and GF benefit to the mechanical properties, while EG is good for flame retardancy. Proper ingredient of additive can lead to good flame retardancy and mechanical properties of the RPUF. © 2013 Wiley Periodicals, Inc.


Hu S.,China University of Mining and Technology | Hu S.,Key Laboratory of Gas and Fire Control for Coal Mines | Wang E.,China University of Mining and Technology | Wang E.,Key Laboratory of Gas and Fire Control for Coal Mines | Liu X.,China University of Mining and Technology
International Journal of Damage Mechanics | Year: 2015

The dual pore structure of coal and occurence of gas adsorption make gas-bearing coal different from other non-adsorptive porous materials, and therefore interactions between coal and gas cannot be accurately described by Terzaghi effective stress. Considering adsorbed-gas-induced swelling stress and erosion, and pore/fracture-induced damage and failure to coal skeleton, the new effective stress equation for three-phase medium composed of free gas, adsorbed gas and coal skeleton is established. It can be used to reveal the effects of the spatial and temporal distribution and evolution of coal pores/fractures under different stress conditions on coal's mechanical deformation and damage characteristics, and to quantify the erosion effects of adsorbed gas on coal from a physicochemical point of view. Based on the basic principles of irreversible thermodynamics, a dual pore elastic-brittle-plastic damage constitutive model of gas-bearing coal is established. The model is further verified through the full stress-strain experiments and the adsorption-induced swelling experiments of gas-bearing coal under different axial pressures, and compared with the elasticoplasticity model established based on Terzaghi effective stress. The results show that the dual pore damage constitutive model could better describe the gas-coal interaction mechanism, and solve the fluid-solid coupling problems in gas and coal engineering practices. © The Author(s) 2015.

Loading Key Laboratory of Gas and Fire Control for Coal Mines collaborators
Loading Key Laboratory of Gas and Fire Control for Coal Mines collaborators