Experimental Research on the Impactive Dynamic Effect of Gas-Pulverized Coal of Coal and Gas Outburst

et al. 2020

Energies

Effectively avoiding methane accidents is vital to the security of manufacturing minerals. Coal mine methane accidents are often caused by a methane concentration overrun, and accurately predicting methane emission quantity in a coal mine is key to solving this problem. To maintain the concentration of methane in a secure range, grey theory and neural network model are increasingly used to critically forecasting methane emission quantity in coal mines. A limitation of the grey neural network model is that researchers have merely combined the conventional neural network and grey theory. To enhance the accuracy of prediction, a modified grey GM (1,1) and radial basis function (RBF) neural network model is proposed, which combines the amended grey GM (1,1) model and RBF neural network model. In this article, the proposed model is put into a simulation experiment, which is built based on Matlab software (MathWorks.Inc, Natick, Masezius, U.S). Ultimately, the conclusion of the simulation experiment verified that the modified grey GM (1,1) and RBF neural network model not only boosts the precision of prediction, but also restricts relative error in a minimum range. This shows that the modified grey GM (1,1) and RBF neural network model can make more effective and precise predict the predicts, compared to the grey GM (1,1) model and RBF neural network model.

Section: Of 15mentioning

confidence: 99%

Research on the Method of Methane Emission Prediction Using Improved Grey Radial Basis Function Neural Network Model

Yang

et al. 2020

Energies

“…Based on the fact that the current bottom coal cutting height of fully mechanized top coal caving face in China is generally 2.0-3.0 m and some reach 3.8 m, the application of a coal seam with a thickness greater than 14 m thick is limited. With the increase of coal cutting height in the bottom layer, the ventilation section can be increased, the gas can be prevented from exceeding the limit, the coal caving space can be increased, the mining and caving ratio can be optimized, and the coal caving efficiency can be increased, which can meet the technical requirements of extrathick coal seam and also meet the relevant provisions of the national coal mine safety regulations [10][11][12][13][14]. e working resistance of the caving support is less than that of the large mining height support.…”

Section: Introductionmentioning

confidence: 99%

Research on the Influence of Mining Height on the Movement Characteristics of Overlying Strata during Extremely Thick Coal Seam Fully Mechanized Sublevel Caving Mining

Yang

Wei

Advances in Civil Engineering

2021

The study of the effects of mining height on overlying strata movement and underground pressure characteristics during extremely thick coal seam fully mechanized sublevel caving mining is very important for choosing the reasonable mining height and the support. Based on the geological setting and mining conditions at the Xiegou Coal Mine, the results of the physical simulation test and the numerical simulation technology will be used. Some conclusions can be drawn as follows: (1) With the mining height increase, the top coal gradually converted from tensile failure to shear damage, and the coal wall gradually transformed from shear failure to tensile damage. (2) When the mining height is 7.5 m, the full-seam collapse distance, the immediate first weighting interval, and the main roof first weighting length are shorter than that when the mining height is 4m, and the periodic weighting length for the two mining heights is almost the same. (3) With mining height increase, the initial mining stage and the transition stage become shorter, and the production rates become better. (4) The law of the abutment pressure peak and the sphere of influence increase slightly, and the working resistance of support needed to be strengthened. (5) The subsidence quantity of the top coal in the control area increases along with the mining height in a quadratic polynomial way but decreases along with the initial supporting force in a negative logarithmic rule. (6) After assigning the subsidence, the regression relation between the initial supporting force and the mining height is a quadratic polynomial.

“…Although the mechanism of coal and gas outbursts is still unclear, many outburst case studies confirm intense coal fragmentation and pulverization resulting from rapid gas desorption and expansion together with rapid ejection of the pulverized coal and gas as a two-phase flow (Guo et al 2016;Jin et al 2018;Sun et al 2018;Xu and Jiang 2017). At macroscale this solid-fluid interaction may be regarded as an equivalent fluid mixture responding with a rheology dependent on its solid content.…”

Section: Introductionmentioning

confidence: 99%

Near-source characteristics of two-phase gas–solid outbursts in roadways

Zhou

Zhang

et al. 2020

Int J Coal Sci Technol

Coal and gas outbursts compromise two-phase gas–solid mixtures as they propagate as shock waves and flows from their sources. Propagation is influenced by the form of the outburst, proximity to source, the structure and form of the transmitting roadways and the influence of obstacles. The following characterizes the propagation of coal and gas outbursts as two-phase gas–solid flows proximal to source where the coupled effects of pulverized coal and gas flows dominate behavior. The characteristics of shock wave propagation and attenuation were systematically examined for varied roadway geometries using experiments and numerical models. The results demonstrate that the geometry of roadway obstructions is significant and may result in partial compression and sometimes secondary overpressurization in blocked and small corner roadways leading to significant attenuation of outburst shock waves. The shock waves attenuate slowly in both straight and abruptly expanding roadways and more significantly in T-shaped roadways. The most significant attenuation appears in small angle corners and bifurcations in roadways with the largest attenuation occurring in blocked roadways. These results provide basic parameters for simplifying transport in complex roadway networks in the far-field, and guidance for the design of coal and gas outburst prevention facilities and emergency rescue.