scholarly journals Coal and Gas Outburst Prevention in Longwalls by Means of Powered Support Unit of New Type

2019 ◽  
Vol 105 ◽  
pp. 01030
Author(s):  
Vladimir Tarasov ◽  
Anatoly Fomin
Keyword(s):  
The State ◽  
Coal And Gas Outburst ◽  
Coal Extraction ◽  
System Support ◽  
Support Unit ◽  
Gas Outburst ◽  
Powered Support ◽  
New Type ◽  
Mining Works ◽  
Roof Support

The paper considers a new type of powered roof support unit in the framework of interaction with geomechanical processes within the ground rock, particularly, in the thermodynamic balance capsule. Its novelty in comparison with similar Russian and foreign technologies consists is in the fact that geomechanical system “support–ground rock” is brought into the state of balance, which increases the safety of mining works at a coal extraction face.

Deformation Analysis for Coal and Gas Outburst Cavity

2011 ◽  
Vol 121-126 ◽  
pp. 2607-2613
Author(s):  
Qian Ting Hu ◽  
Wen Bin Wu ◽  
Guo Qiang Cheng
Keyword(s):  
Damage Zone ◽  
Coal And Gas Outburst ◽  
Gas Content ◽  
Combination Method ◽  
Deformation Analysis ◽  
Failure Zone ◽  
Finite Element Code ◽  
Cavity Volume ◽  
Gas Emission ◽  
Gas Outburst

Outburst cavity formed during coal and gas outburst can be pear shaped, elliptical, or just like an irregularly elongated ellipsoid, its capacity is always smaller than the volume of ejected coal. And the gas emission quantity is almost 4 to 10 times as gas content in ejected coal. These are two different expressions of the same problem. To find the reasons for the decrease of outburst cavity volume and the increase of gas emission quantity per ton, by using the finite element code ANSYS, the damage zone and the failure zone of the outburst cavity were determined based on the static and dynamic combination method. In this paper, the reason for the decrease of the outburst volume was explained.

Islamists between revolution and the state: an epilogue

2014 ◽  
Vol 7 (2) ◽  
pp. 283-298 ◽  
Author(s):  
Abdul Ghani Imad
Keyword(s):  
Political System ◽  
Arab World ◽  
The State ◽  
Social Needs ◽  
Political Actors ◽  
The Social ◽  
The Face ◽  
Heavy Burden ◽  
New Type ◽  
Political Realities

The problematic addressed in this article is the challenge initiated by the Arab revolutions to reform the Arab political system in such a way as to facilitate the incorporation of ‘democracy’ at the core of its structure. Given the profound repercussions, this issue has become the most serious matter facing the forces of change in the Arab world today; meanwhile, it forms the most prominent challenge and the most difficult test confronting Islamists. The Islamist phenomenon is not an alien implant that descended upon us from another planet beyond the social context or manifestations of history. Thus it cannot but be an expression of political, cultural, and social needs and crises. Over the years this phenomenon has presented, through its discourse, an ideological logic that falls within the context of ‘advocacy’; however, today Islamists find themselves in office, and in a new context that requires them to produce a new type of discourse that pertains to the context of a ‘state’. Political participation ‘tames’ ideology and pushes political actors to rationalize their discourse in the face of daily political realities and the necessity of achievement. The logic of advocacy differs from that of the state: in the case of advocacy, ideology represents an enriching asset, whereas in the case of the state, it constitutes a heavy burden. This is one reason why so much discourse exists within religious jurisprudence related to interest or necessity or balancing outcomes. This article forms an epilogue to the series of articles on religion and the state published in previous issues of this journal. It adopts the methodologies of ‘discourse analysis’ and ‘case studies’ in an attempt to examine the arguments presented by Islamists under pressure from the opposition. It analyses the experiences, and the constraints, that inhibit the production of a ‘model’, and monitors the development of the discourse, its structure, and transformations between advocacy, revolution and the state.

scholarly journals Mechanical criterion for coal and gas outburst: a perspective from multiphysics coupling

2021 ◽  
Author(s):  
Ting Liu ◽  
Baiquan Lin ◽  
Xuehai Fu ◽  
Ang Liu
Keyword(s):  
Control Method ◽  
Risk Identification ◽  
Controlling Factors ◽  
Gas Pressure ◽  
Critical Values ◽  
Coal And Gas Outburst ◽  
Strong Interactions ◽  
Gas Outburst ◽  
Multiphysics Coupling ◽  
Coal Strength

AbstractAlthough a series of hypotheses have been proposed, the mechanism underlying coal and gas outburst remains unclear. Given the low-index outbursts encountered in mining practice, we attempt to explore this mechanism using a multiphysics coupling model considering the effects of coal strength and gas mass transfer on failure. Based on force analysis of coal ahead of the heading face, a risk identification index Cm and a critical criterion (Cm ≥ 1) of coal instability are proposed. According to this criterion, the driving force of an outburst consists of stress and gas pressure gradients along the heading direction of the roadway, whereas resistance depends on the shear and tensile strengths of the coal. The results show that outburst risk decreases slightly, followed by a rapid increase, with increasing vertical stress, whereas it decreases with increasing coal strength and increases with gas pressure monotonically. Using the response surface method, a coupled multi-factor model for the risk identification index is developed. The results indicate strong interactions among the controlling factors. Moreover, the critical values of the factors corresponding to outburst change depending on the environment of the coal seams, rather than being constants. As the buried depth of a coal seam increases, the critical values of gas pressure and coal strength decrease slightly, followed by a rapid increase. According to its controlling factors, outburst can be divided into stress-dominated, coal-strength-dominated, gas-pressure-dominated, and multi-factor compound types. Based on this classification, a classified control method is proposed to enable more targeted outburst prevention.

The Impact Analysis of Coal’s Elastic Energy on the Coal and Gas Outburst Shock Wave

2012 ◽  
Vol 616-618 ◽  
pp. 390-395
Author(s):  
Cheng Wu Li ◽  
Tian Bao Gao ◽  
Shan Yang Wei ◽  
Teng Li
Keyword(s):  
Shock Wave ◽  
Elastic Energy ◽  
Impact Analysis ◽  
Dynamic Theory ◽  
Coal And Gas Outburst ◽  
Calculation Formula ◽  
Theory Analysis ◽  
Gas Outburst ◽  
Quantitative Calculation ◽  
The Impact

According to the gas dynamic theory, this paper deduces the approximate calculation formula on elastic energy of a tons of coal through theory analysis, and then gets the quantitative calculation method between incident overpressure and reflected overpressure of the coal and gas outburst shock wave. The calculation formula in this paper is in line with the measured values, and so its validity has been verified. The analysis result shows that the effect of the elastic energy during the process of coal and gas outburst should be considered when the depth of the coal seam is great and the coal’s modulus of elasticity is small.

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