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This paper introduces occurrence characteristics of coal bed methane in China, and analyses the influence of coal seam permeability on coal mine methane extraction. In addition, it presents the mechanism of increasing permeability by pressure relief. Lastly, the methane extraction technologies are discussed, and the applicable conditions of these technologies are analyzed. It is seen that choosing appropriate methane drainage technology, often in combination with several technologies including ground drilling, underground drilling, and pressure relief and permeability improving measures, is crucial for geological complex coal seam, especially low permeability soft coal seam.

The variation of coal body electrical parameters are important parameters for researches on the propagation of electromagnetic radiation and acoustic emission in coal. Therefore, experiments of coal body electrical parameters under triaxial stress are carried out. Studies have shown that, the resistivity of coal body decreases with the loading of axial compression and confining pressure. And the decline of raw coal is relatively more obvious, while the decline of briquette is smaller. Moreover, the resistivity of coal body retains relatively stable when the stress is greater than 3MPa. With the increase of axial compression and confining pressure, the dielectric constant of coal body will also increase and it will be basically stable when the stress is greater than 3MPa.

In order to research the dust removal process of dust agent in coal working face, we design the proportional adding equipment of mine-used dust-fall agent for static pressure pipes in coal working face and establish the calculation model of process parameters of this equipment combining with pipe flow theory of fluid mechanics, and theoretically analyze the selection rules of components such as the high pressure piston pump and pneumatic motor power.the proportional adding equipment has been applied to coal working face. From the results of the application, this equipment for reducing dust concentration in coal working face (especially PM2.5) has the obvious effect.

The gas-pulverized coal two phase flow law of gas is simulated by the use of the theory of jet after coal and gas outburst. Research results show that as the volume fraction of pulverized coal in outbursts mixture increases, the speed of two phase flow at the exit gradually reduces, jet core length shorter, turbulent longitudinal effect range smaller, jet width narrower. And dynamic head mainly concentrates in the jet core area and its distribution is more uniform in the roadways. The maximum speed of outburst two-phase flow decreases with the adding volume fraction of pulverized coal, that is higher the coal content in outburst mixtures, smaller the maximum speed after outburst. But a high content of coal have higher impact strike force which can cause major damage effect. The research may provide some theoretical basis for setting underground safety facilities, mine personal protection, disaster warning and emergency rescue.

According to the questions of long eliminating coal and gas outburst period, large projects and slow driving came from the regional measurement of drilling hole ,the paper select 2371 (1) rail transport roadway as experiment for using along seam long drilling as a regional measurement to eliminate coal and gas outburst. Since the regional measurement of along seam long drilling had been carried out, the remaining gas content decreased more than 60％, max Smax was 5.4kg/m, max qmax was 2.01/min.Both Smax and qmax were not beyond the standard. Gas concentrations were not overrun. Gas emission decreased in the roadway afterward. The regional measurement eliminated the risk of coal and gas outburst in effect. Heading face promoted 423m forward safely. The max January footage could reach 120m.Achieve driving of heading face safely and fast.

The experiment studied the variation of coal electric parameter using coal electric parameter testing system designed and processed by themselves. Raw coal sample and moulded coal sample were chosen as the study object. Studies have shown that the resistivity of coal sample decreases with increasing temperature. The resistivity of raw coal decreases significantly as the temperature increases, while the extent of decrease in moulded coal small. The dielectric constant of coal body decreases with increasing temperature. At the same temperature, the dielectric constant and the resistivity of moulded coal are both smaller than that of the raw coal. There are some theory and reference value of the experimental results for predicting coal and gas outburst with electromagnetic radiation.

To improve the low-permeability coal seam gas drainage and gas prevention and to seek the methods to improve the permeability of low-permeability coal, the experimental study on supercritical CO2 on coal was conducted in the laboratory conditions, and the experiment on pseudo-triaxial permeability testing for coal samples, with and without supercritical CO2, was conducted. The results show that due to the effect of supercritical CO2 on coal like physi-chemistry, the porosity of coal was changed, which markedly varied the permeability of coal samples before and after the effect of supercritical CO2; the permeability of the experimented coal samples was significantly higher than before, and average permeability increased by nearly an order of magnitude under the same volume-stress.

Insufficient investment in safety and irrational of security investment structure is one of the causes of accidents are occurring in the coal industry. This article takes fuzzy comprehensive evaluation on the rationality of the mine safety investment structure by M (1,2,3) model on the basis of the analysis of the correlation between coal mine safety input and safety production status. The evaluation results show that personnel training and investment in safety technology is the key of accident prevention, management investment is the main factor of affecting the rationality of coal mine safety investment structure; the fuzzy comprehensive evaluation based on M(1,2,3) model can improve the precision of fuzzy comprehensive evaluation.

Electromagnetic emission (EME) is a kind of physical phenomenon accompanying the process of deformation and fracture of loaded coal and rock and it is of importance in quantitatively analyzing its characteristics. This will reveal the process of deformation and fracture of coal and predicting dynamic disasters in coal mines. In this study, the G-P (Grassberger and Procaccia) algorithm, calculation steps of the (if only 1 dimension) correlation dimension of time series and the identification standards of chaotic signals are introduced. Furthermore, the correlation dimensions of EME and the acoustic emission (AE) signals of time series during deformation and fracture of coal bodies are calculated and analyzed. The results show that the time series of pulses number of EME and the time series of AE count rate are chaotic and that the saturation embedding dimensions of a K3 coal sample are, respectively, 5 and 6. The results can be used to provide basic parameters for predicting of EME and AE time series.

The coal seam being mined by #3103 working face of Shangzhuang Coal Mine is relatively close to its adjacent seam. Moreover, the adjacent seam contains considerably high gas content. Therefore, in order to prevent excessive gas exceeding the stipulated limit as a result of massive gas emission from the adjacent seam during the initial collapse of the roof, forced caving scheme is worked out to deal with the roof of the working face based on the site conditions. On the one hand, pre-breaking blasting with deep holes adds up to the fissures in the upper adjacent seam, which not only enhances the effects of gas drainage in the adjacent seam in high position roadway, but prevents coal and gas outburst accident arising from floor collapse in large area. The practices proved that the forced caving scheme is feasible and effective to prevent outburst in the working face with upper adjacent seam.