scholarly journals Expansionary Evolution Characteristics of Plastic Zone in Rock and Coal Mass Ahead of Excavation Face and the Mechanism of Coal and Gas Outburst

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 984
Author(s):  
Hongtao Liu ◽  
Linfeng Guo ◽  
Xidong Zhao
Keyword(s):  
Plastic Zone ◽  
Mechanical Analysis ◽  
Coal And Gas Outburst ◽  
Analysis Model ◽  
Change Of Direction ◽  
Gas Outburst ◽  
Evolution Characteristics ◽  
Prediction And Prevention ◽  
Coal And Gas Outbursts ◽  
Scientific Challenge

Factors leading to coal and gas outbursts are complicated, and the accuracy of predicting outbursts remains difficult to achieve. Therefore, coal and gas outburst risk are still a scientific challenge in the fields of mining, geology, safe engineering, and rock mechanics. Theories explaining and predicting coal and gas outbursts associated with restored strain and gas energy are hot topics. Based on numerical modelling, the evolution of a plastic zone ahead of an excavation face with change of direction and magnitude of regional pre-mining stress field were analyzed. A mechanical analysis model for the expansionary evolution process of the plastic zone ahead of the excavation face was constructed, and the expansionary evolution characteristics of plastic zone ahead of the excavation face were analyzed. The physical and mechanical process and basic conditions for the initiation and development of coal and gas outbursts induced by evolution of plastic zone were discussed. The research provides some new insights into the mechanism, prediction, and prevention of goal and gas outbursts.

scholarly journals Coal and Gas Outburst Affected by Law of Small Fault Instability during Working Face Advance

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Jianyun Lin ◽  
Yujun Zuo ◽  
Kai Zhang ◽  
Wenjibin Sun ◽  
Biao Jin ◽  
...  
Keyword(s):  
Fault Zone ◽  
Coal And Gas Outburst ◽  
Face Advance ◽  
Movement Rate ◽  
Gas Outburst ◽  
Working Face ◽  
Prediction And Prevention ◽  
Small Fault ◽  
Coal And Gas Outbursts ◽  
Overburden Strata

To analyze the effect of small faults in the working face on coal and gas outbursts, the coal and gas outburst accident in the 21431 working face was studied with the 3DEC numerical simulation method, and the main research contents were the change laws of both stresses at the small fault and the overburden strata movement rate in the small fault zone of which the drop height and the strike were designed into different groups. The results show that the risk of small fault slip increases with the advancing working face. In addition, there is a positive correlation between the risk and the small fault throw. The movement rate of overburden strata in the small fault zone increases along with the rising of the small fault throw, which increases the energy transferred to the coal seam from the surrounding rock under the effect of the small fault. Hence, the effect of small faults on the working face on coal and gas outbursts was positively correlated with the small fault throw. Under the influence of a small fault strike, the closer it is to the small fault along the dip distance at the same working face, the greater the risk will be of a coal and gas outburst. And the bigger the small fault strike is, the greater is the stress concentration degree in front of the working face and the more the elastic energy is stored and the greater is the possibility of an outburst. The paper analyzes the influence of small faults on coal and gas outbursts in the working face, which has reference significance for the prediction and prevention of coal and gas outburst disaster in the working face.

scholarly journals Economic Assessment of Methods of Coal and Gas Outburst Prevention in the Extraction of Coalfaces

2020 ◽  
Vol 3 (1) ◽  
pp. 379-393
Author(s):  
Vlastimil Hudeček ◽  
Michal Vaněk ◽  
Igor Černý
Keyword(s):  
Economic Assessment ◽  
Simulation Method ◽  
Coal And Gas Outburst ◽  
Optimal Method ◽  
Gas Outburst ◽  
Drift Length ◽  
Mutual Comparison ◽  
Coal And Gas Outbursts ◽  
The Individual ◽  
Prevention Methods

AbstractIn this paper, the authors focused on the assessment of the individual methods to prevent coal and gas outbursts. The first part deals with a characteristic of this anomalous phenomenon and some basic methods of coal and gas outburst prevention. The second part presents the economic assessment of the costs necessary to ensure the possible prevention methods in the coalface 080 211 in the locality of the Paskov Mine, Mining Plant 3, OKD as, Czech Republic. In this coalface, a simulation method was used for calculating costs for the drift length of 100 m for the use of various prevention methods (irrigation, relief boreholes, relief blasting). The results show the cost of preventive measures during mining intended to eliminate and protect against the formation of coal and gas outbursts. The measures are compared applying the principle of the decision analysis. Four criteria are used for the mutual comparison of the methods (costs, effort, efficiency, time consumption). The comparison has shown that the optimal method to prevent coal and gas outbursts is irrigation.

scholarly journals Study on Catastrophe Theory of Activation-Induced Prominence of Faults under Dynamic Disturbance

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Yujun Zuo ◽  
Hao Wang ◽  
Meilu Yu ◽  
Xiaoxiao Dou ◽  
Zhonghu Wu ◽  
...  
Keyword(s):  
Catastrophe Theory ◽  
External Input ◽  
Surrounding Rock ◽  
Coal And Gas Outburst ◽  
External Energy ◽  
Dynamic Disturbance ◽  
Gas Outburst ◽  
Prediction And Prevention ◽  
Mining Disturbance ◽  
The Stability

In view of the phenomena of coal and gas outburst induced by fault activation under dynamic disturbance, a mechanical model of faults and surrounding rock mechanics was established based on the theory of fold catastrophe. Moreover, the dynamic disturbance factors were introduced and analyzed to analyze the influencing factors of outburst coal rock outburst. Through theoretical analysis, it shows that the thinner the fault medium is, the more energy the external input is required for system instability, and the external energy can reflect the stability of the system. When the width of fault media is fixed, the stronger the mining disturbance, the less energy the external input is required for system instability; on the contrary, the weaker the mining disturbance is, the more energy the external input is required for system instability. In addition, through the equation of conservation of kinetic energy, it can be seen that the stronger the mining disturbance, the greater the critical value of the surrounding rock thickness. The paper introduces the dynamic disturbance parameters through the catastrophe theory and analyzes the influence of the existence of faults on coal and gas outburst in detail, which provides a new theoretical basis for the prediction and prevention of coal and gas outburst disasters.

scholarly journals Analysis of the Occurrence Mechanism for Coal and Gas Outburst Based on Multiple Discriminant Indices

2019 ◽  
Vol 2019 ◽  
pp. 1-17 ◽  
Author(s):  
Hai Rong ◽  
Hongwei Zhang ◽  
Bing Liang ◽  
Weihua Song
Keyword(s):  
Coal Mine ◽  
Regional Distribution ◽  
Geological Structure ◽  
Coal And Gas Outburst ◽  
Prevention Measures ◽  
Distribution Law ◽  
Risk Levels ◽  
Gas Outburst ◽  
Prediction And Prevention ◽  
Occurrence Mechanism

In order to reveal the occurrence mechanism of coal and gas outburst and optimize the measures to prevent the disaster, a coal mine in Henan Province was undertaken as the research background. Based on the geological and mining conditions of the coal mine, the gas geological analysis method is applied to determine the outburst occurrence and to classify the risk levels. A multifactor pattern recognition method is used to determine the risk probability of the dynamic disasters such as coal and gas outburst. The relationship between geological structure, rock mass stress, and mine dynamic hazards is determined using geo-dynamic division method and FLAC3D numerical simulation. The occurrence and manifestation characteristics of the dynamic hazards are determined. COMSOL Multiphysics software is used to evaluate the original prevention measures and to optimize the measures. The research results determine the main influencing factors and regional distribution law of coal and gas outburst, which is of great significance to the risk prediction and prevention of dynamic disasters such as coal and gas outburst.

A new method for coal and gas outburst prediction and prevention based on the fragmentation of ejected coal

Fuel ◽  
2021 ◽  
Vol 287 ◽  
pp. 119493
Author(s):  
Chaolin Zhang ◽  
Enyuan Wang ◽  
Jiang Xu ◽  
Shoujian Peng
Keyword(s):  
Coal And Gas Outburst ◽  
New Method ◽  
Gas Outburst ◽  
Prediction And Prevention

Characteristics of Coal and Gas Outburst within Gas Geological Units in Qidong Mine

2013 ◽  
Vol 734-737 ◽  
pp. 45-51
Author(s):  
Ai He Chen ◽  
Dong Ji Lei ◽  
Yu Gui Zhang
Keyword(s):  
Magmatic Rock ◽  
Coal And Gas Outburst ◽  
Gas Content ◽  
Coal Bed ◽  
Burial Depth ◽  
Gas Outburst ◽  
Prediction And Prevention ◽  
Gas Occurrence ◽  
Tectonic Coal ◽  
Geological Units

The precise mechanism of the coal and gas outburst is still unresolved, but productive practices in Qidong mine have testified that the coal and gas outburst accidents are predominantly associated with the belt of geological structure, the zone of tectonic coal occurrence and the area of the stress concentration. So it is very important to study characteristics of coal bed gas geology for coal bed gas prediction and prevention. Using gas-geology theory and method, the research focused on the factors of coal and gas outburst, such as coal bed gas occurrence, stress distribution, tectonic coal occurrence and magmatic rock presence within Qidong mine. The result shows that: Qidong mine district could be divided into 4 geological units by 3 faults as the boundary, the faults of Weimiao fault, F2, and F5; there are different conditions and main controlling factors of coal bed gas occurrence within four geological units. The unit I of geology: coal bed gas occurrence conditions are simpler, mainly contacted with the coal burial depth; the unit II: the conditions are more complex, predominantly associated with fault structures; the unit III: as a result of the presence of igneous intrusions, coal bed gas content in unit III is the highest within the whole mine; the unit IV: major factor of the conditions is the fold caused by strata uplift, which also leads to a large number of gas emissions. 25 coal and gas outburst accidents all occurred within the unit II of geology.

scholarly journals Effect of Principal Stress Field on the Development of Plastic Zone ahead of the Gateroad

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4356
Author(s):  
Hongtao Liu ◽  
Linfeng Guo ◽  
Xidong Zhao ◽  
Pengfei Wang
Keyword(s):  
Stress Field ◽  
Plastic Zone ◽  
Principal Stress ◽  
Maximum Principal Stress ◽  
Coal And Gas Outburst ◽  
Lagrangian Analysis ◽  
Important Indicator ◽  
Gas Outburst ◽  
Minimum Principal Stress ◽  
Long Time

The distribution of a plastic zone ahead of a gateroad plays a significant role in maintaining the long-term stability of mining spaces. For a long time, the principal stress field such as the values, the direction, etc. have been observed to have impacts on plastic zone development, but has not been looked into deeply and systematically. To this end, the influence of principal stress field including the maximum principal stress (P1), the angle between the P1 direction and the Z-axis (α), the minimum principal stress (P3), and the ratio of maximum principal stress to minimum principal stress (P1/P3) on the expansion of the plastic zone ahead of the gateroad is investigated by the (Fast Lagrangian Analysis of Continua) FLAC3D models. The results show that: (1) The plastic zone volume increases first and then decreases with the increase of α, and the direction of butterfly-shaped plastic zone ahead of gateroad is rotating with the evolution of α. (2) The plastic zone volume ahead of excavation face increases gradually with the increase of P1/P3. Mutagenicity of butterfly-shaped plastic zone occurs ahead of the gateroad under a certain value of P1/P3. (3) With the increase of P1 and decrease of P3, the plastic zone volume is of exponential growth. The plastic zone volume approaches infinity when the critical value of maximum principal stress ([P1]) and the minimum principal stress ([P1]) is obtained. (4) The study of the effect of principal stress field on the expansion of plastic zone ahead of the gateroad is helpful for revealing the mechanisms of coal and gas outbursts. The critical stress state of butterfly-shaped plastic zone mutagenicity ahead of the gateroad can be used as an important indicator for assessing the risk of coal and gas outburst. The research can also guide the prevention of coal and gas outburst ahead of the gateroad.

scholarly journals Study on Plastic Zone Distribution Characteristic of Coal and Rock Mass in Excavation from Crosscut Coal

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Chengwu Li ◽  
Xiaoqian Zhang ◽  
Chengmin Wei ◽  
Yao Nie
Keyword(s):  
Rock Mass ◽  
Stress Distribution ◽  
Plastic Zone ◽  
Morphological Characteristics ◽  
Coal And Gas Outburst ◽  
Distribution Characteristics ◽  
Prevention Measures ◽  
Shape Distribution ◽  
Gas Outburst ◽  
Working Face

Coal and gas outburst is a serious disaster in the mining, and crosscut coal is the most prone to cause the coal and gas outburst. In order to study the mechanism of outburst, this paper studied the stress distribution characteristics in front of the working face in the process of rock roadway driving before implementing crosscut coal firstly. On this basis, the hypothesis of stress distribution on the “strong and soft face” of coal-rock mass was proposed. And by using the hypothesis, the mechanical equation for the parameter changes of the plastic zone in front of the working face in crosscut coal was established, and the width and morphological characteristics of the plastic zone in crosscut coal were analyzed. The results show that during the process, as the working face moves forward, the shape distribution of the plastic zone in front of the working face changes from the “semielliptical” to “semibutterfly,” And based on the distribution characteristics of plastic zone in working face in crosscut coal, modification proposals for outburst-prevention measures were proposed and provided technical support for the outburst-prevention measures and key parameters setting to prevent the coal outburst in crosscut coal.

scholarly journals Geometric Model for Physical Simulation System of Coal and Gas Outburst

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Shutong Zhang
Keyword(s):  
Physical Simulation ◽  
Statistical Data ◽  
Geometric Model ◽  
Simulation System ◽  
Coal And Gas Outburst ◽  
Gas Content ◽  
Statistical Characteristics ◽  
Geometrical Parameters ◽  
Gas Outburst ◽  
Coal And Gas Outbursts

The physical simulation system is an important means to study the mechanism of coal and gas outburst. The small- and medium-sized coal and gas outbursts account for the largest proportion in China. So, the paper focuses on small- and medium-sized coal and gas outbursts based on key physical rules and their statistical characteristics. According to the geometric parameters statistical data of more than 100 caverns, the proportion of outburst caverns whose depth is less than 5 m is 80%, and whose depth is more than 6 m is 13%. The ratio of depth and cavern outlet’s diameter is 2.58–7.31. There are statistical relationship of 2 times between coal’s and cavern’s volume, and between gas emission volume per ton and gas content in seam. Then, the cavern of coal and gas outburst is simplified as an ellipsoid, and the shape of cavern outlet is simplified as a circle. The cavern’s and the prototype’s geometrical parameters of small and medium coal and gas outbursts were deduced. The depth of cavern is 5 m, width is 4 m, and diameter of cavern outlet is 0.68–1.94 m. The depth of coal and outburst prototype is 12.3 m, width is 6.5 m, and diameter of cavern outlet is 0.68 m. In order to guarantee the movement similarity, according to the relationships among statistical data of outburst coal particle’s size, cavern outlet’s size, and height of tunnel, the minimum cavern outlet’s size was calculated. Select 10 times the coal particle’s size (5 mm) as the smallest size. Then, maximum geometric similarity ratio of coal and gas outburst was deduced, and it is 13.6. The minimum geometrical parameters of coal and outburst similar model were obtained. Its depth is 0.9 m, width is 0.48 m, and diameter of cavern outlet is 50 mm. According to the results, the physical simulation system was developed. The results provide support to carry out physical simulation experiment of coal and gas outburst.

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