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Mastering the shape, size and variation of goaf is important to goaf disposal, disaster control and mining optimization. A method is presented to realize goaf precision monitoring and 3D visualization by cavity monitoring system (CMS). On this basis, Goaf 3D modeling, goaf-model visualization transmission and display based on network, visible calculation method of mining loss and ore dilution during actual mining, 3D blasting design of complicated boundary pillar during actual mining, dynamic monitoring of goaf, stability analysis of tunnel above goaf, 3D survey and analysis of tunnel destruction caused by goaf collapse, numerical simulation of goaf stability and all other related technologies are researched and applied by using numerical software and network. Results showed that 3D space information of goaf could be accurately acquired by CMS, and visualization application based on the information is reliable. These research and application are of great practical significance to recover mineral resources and assure safe mining. [ABSTRACT FROM AUTHOR]

Abstract: In order to reduce spontaneous combustion in goaf at high methane mine, spontaneous oxidation zone distribution in goaf under methane stereo drainage is numerically studied by Fluent software. For the actual case of 8403 working face in Yang-Quan, According to the combination of gas velocity and oxygen concentration distribution, the oxidation zone distribution of horizontal and vertical surfaces are determined. The results shows that the distribution of spontaneous oxidation zone is asymmetrically at horizontal surfaces, the width of spontaneous oxidation zone of inlet side is wider than outlet side; at the vertical surfaces, the spontaneous oxidation zone is below 20 meters. By the contrast of the numerical oxygen concentration and measured oxygen concentration, good agreement is obtained, which shows that the numerical results is reliable. The methane concentration distribution shows that inner tail-roadway can effectively reduce methane concentration at working face''s upper corner, and high drainage roadway can reduce methane concentration in the whole goaf. [Copyright &y& Elsevier]

Abstract: Development of air leakage in goaf and residual coal self-ignition Characteristics Study on the spontaneous combustion of residual coal in goaf in the early prediction, prevention and control management has very important significance. Based on the mining coal working surface pressure energy distribution and Sign gas detection of Nanzhuang coal mine working face within the airtight air leakage condition and the O2, CO, CO2, C2H6, C2H4, C3H8 and other Sign gas concentration variation, identified 4601, 8808 lane closed walls within Coal body broken belt of spontaneous combustion danger area and its morphology. According to the spontaneous combustion of residual coal in goaf features from strengthening ventilation management, strengthening the gas and temperature detection, perfusion of three-phase foam developed a comprehensive system for the prevention and control of coal spontaneous combustion [Copyright &y& Elsevier]

Abstract: The gas, oxygen, carbon monoxide and acetylene concentration and the temperature distribution of longwall goaf areas were analyzed by means of burying pipes and temperature sensor. Furthermore, the regulation of “three zones” distribution of 1361 face in Jinyuan colliery by the oxygen concentration and the temperature distribution has been worked out, and the limited velocity of the working face has been marked off. The research results showed that the gas concentration was low intake airflow roadway along goaf towards direction. The goaf gas concentration in return airway was far higher than intake airflow roadway. There was not combustion phenomenon during the test in the 1361 goaf of the coal mining. Meanwhile, the results also confirmed mining extraction process source of gas accumulation in face corner, also can be used for providing the basis of enacting fire prevention measures in the goaf and gas management measures for face corner. [Copyright &y& Elsevier]

Abstract: The risk of spontaneous combustion in goaf of fully mechanized coal face with big dip and hard roof is high, and gas monitoring is more difficult. The method of dividing spontaneous combustion “three-zone” by temperature rise and CO concentration in goaf was presented in this paper. Tubes and temperature probes were buried in goaf at NO.7162 fully mechanized coal face in Longdong Coal Mine to monitor the temperature and gas concentration in goaf. The regularity of temperature and gas concentration changing with the advancing face was analyzed. According to the change of temperature and CO concentration in goaf, the range of spontaneous combustion “three-zone” was determined and verified by oxygen concentration. The method of dividing “three-zone” by temperature rise and CO concentration is simple, accurate and reliable, and provides scientific basis for spontaneous combustion prevention in goaf. [Copyright &y& Elsevier]

Abstract: Gas explosion is one of the most serious accidents threatening the safety of the coal mines in China. The goaf, especially the upper corner, tends to accumulate methane and leak air, which constitutes a potential gas explosion source. Control of the methane in this area remains a concern among coal mine operators. In response to spontaneous combustion that leads to explosion, it is supposed that a porous medium, foam ceramics, be installed in the conjuncture between the working face and goaf according to the “Three Zones” of spontaneous combustion and high- temperature zone distribution in gob area. Theoretical analysis and experimental research demonstrate that, due to numerous collisions with walls, the foam ceramics can significantly destroy the free radicals generated from chemical reactions in gas combustion, inhibit the heat release, making the chemical reaction not self-sustained. Consequently, flame propagation is suppressed and shock wave attenuated. Given the advantages of foam ceramics of large porosity, high temperature resistance and powerful shock resistance, it is supposed that the foam ceramics be installed properly to isolate the gas explosions in the goaf. However, such installation needs further validation experimentally and on the site. [Copyright &y& Elsevier]

Abstract: Taking Wang Tai Coal Mine2304 working surface as the object of study, the gaseous components along with the advancing working face were examined through burying pipe sampling in the goaf, the change rule of oxygen volume fraction along with the depth of working face was investigated. According to the measure result of gas concentrations, this paper determined the distribution of coal spontaneous combustion oxidation “three zones” in Wang Tai Coal 2304 working face. At the same time, based on the Darcy law, the numerical simulation was performed for the single return air roadway by using the Fluent software, 80m, 160m and 240m away from the working surface respectively. In the three situations, the paper researched the distribution of flow field, the O2 concentration field and the CO concentration field, analyzed the change rule of oxidation zone along with the advancing working face. Wang Tai Coal 2304 working face contain spontaneous combustion “three zones”: cooling zone (0∼38m), oxidation zone (38m∼145m) and suffocation zone (> 145m); the width of oxidation zone along with single return air roadway from the face length approximately linearly increases. [Copyright &y& Elsevier]

Abstract: Residual coal in goaf easily causes spontaneous combustion, and provides a long-term existence fire source, then easily leads to secondary gas explosion. This paper has a systematic study on the laws of gas flow and heat transfer in goaf pre-and post residual coal spontaneous combustion by numerical simulation. Multi-field coupling changed laws of gas-air mixed gas 3D seepage field, concentration field and temperature field pre-and post residual coal spontaneous combustion in goaf have been obtained by discreting mathematical model equations. The numerical simulation results coincide well with site observation data. [Copyright &y& Elsevier]