scholarly journals Gas Distribution Mechanism in Goaf during Combined Drainage of Upper Corner Buried Pipeline and Intubation for Thick Coal Seams

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 4) ◽  
Author(s):  
Zhe Li ◽  
Fangtian Wang ◽  
Shuai Ren ◽  
Guannan Liu
Keyword(s):  
Buried Pipeline ◽  
Coal Seams ◽  
Gas Drainage ◽  
Gas Concentration ◽  
Geological Conditions ◽  
Key Issues ◽  
Fluent Software ◽  
Gas Control ◽  
Drainage Effect ◽  
And Control

Abstract The prevention of gas overrun in the panel is one of the key issues on green mining. In this paper, a physical goaf model was established based on the geological production conditions of a coal seam in a coal mine in Henan Province, and the combined drainage technology by burying and spilling pipeline in the upper corner was proposed. The Fluent software was used to simulate the changes of gas mass fraction and flow field distribution when the gas is extracted from the goaf without the gas pipeline, with a single buried pipeline, and with the combination of buried and spilled pipelines. Analysis and simulation showed that in the absence of drainage pipelines, the gas concentrations in both the return airway and the upper corner are up to 1.2%, which failed to meet the gas prevention and control standard on the mine. In the case of gas drainage with a single buried pipeline, the average gas concentration in the return airway was 0.7%, and only the gas concentration in the upper corner was up to 1.1%, which failed to meet the gas control standards on the mine’s panel. However, the maximum gas concentration in the combined drainage was reduced from 1.1% to 0.6%, which indicates that the technology can greatly reduce gas concentration, but there is still a gap from the mine’s gas control standard. Therefore, the impacts of the lengths of pipelines buried in different goafs on the gas drainage effect in the goaf were studied, and it was concluded that the reasonable length of pipelines buried in the goaf under the geological conditions was 20 m. This technology not only solves the problem of gas overrun in the panel but also realizes the utilization of gas resources in the goaf. The research results are of guiding significance for pipeline laying and the drainage technology in the upper corners on the U-shaped ventilation panel.

scholarly journals Study on Gas Control Methods Optimization for Mining Safety

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Liwen He ◽  
Yingcheng Dai ◽  
Sheng Xue ◽  
Chunshan Zheng ◽  
Baiqing Han ◽  
...  
Keyword(s):  
Coal Seam ◽  
Coal Mine ◽  
Control Measures ◽  
Coal Seams ◽  
Gas Emission ◽  
Gas Drainage ◽  
Geological Conditions ◽  
Mining Safety ◽  
Gas Control ◽  
Outburst Hazard

Effective gas control is of significance for safe efficient coal mining in Haizi Coal Mine and other mines with similar geological conditions. This study concentrates on gas control theories and techniques in multiple coal seams of Haizi Coal Mine (No. 7, No. 8, No. 9, and No. 10 coal seam from top to bottom). To minimize risk of high gas emission and outburst hazard, No. 10 seam was mined first as a protective seam prior to the mining of its overlying outburst-prone No. 7, No. 8, and No. 9 seam. Four gas drainage measures were determined for gas control, including cross-measure boreholes into overlying coal seams, surface goaf wells, roof boreholes, and roof gas drainage roadway. These gas control measures, if implemented through entire coal seam extraction, would be possibly uneconomic. An investigation was undertaken to analyze effects of those four measures on gas emission, methane concentration, and gas drainage quantity in No. 2 1024 mining panel of No. 10 seam. Results indicate that the highly expensive gas drainage measure of a roof roadway has poor drainage performance and could be effectively replaced by roof boreholes. When adopting the optimized combination of gas drainage measures, drainage efficiency of No. 7 seam, No. 8 seam, and No. 9 seam could reach 58.64% and decrease gas pressure to be below 0.74 MPa. Outcomes of this study could provide beneficial guidance not only for gas drainage design optimization in Haizi Coal Mine but also for other multiple-seam mines with similar mining and geological conditions, for increasing gas drainage efficiency and guaranteeing mining safety.

scholarly journals Influence of Deformation and Instability of Borehole on Gas Extraction in Deep Mining Soft Coal Seam

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Xue-Bo Zhang ◽  
Shuai-Shuai Shen ◽  
Xiao-Jun Feng ◽  
Yang Ming ◽  
Jia-jia Liu
Keyword(s):  
Pressure Loss ◽  
Drainage System ◽  
Suction Pressure ◽  
Coal Seams ◽  
Gas Drainage ◽  
Soft Coal ◽  
Instability Modes ◽  
Deformation Instability ◽  
Effective Drainage ◽  
Drainage Effect

To study the effects of the three deformation instability modes of gas drainage borehole on gas drainage, the deformation instability mechanism of soft coal seams is analyzed, three deformation instability modes are proposed for soft coal seams, namely, complete holes, collapse holes, and plug holes, and a solid-fluid coupling model incorporating dynamic change of borehole suction pressure is established. The results of the study show the following. (1) When there is no borehole deformation (i.e., complete borehole), the suction pressure loss of drainage system in the borehole is very small, whose effect on gas drainage can be neglected. (2) In case of borehole collapse, the suction pressure loss is big at the collapse segment, and the total suction pressure loss of the drainage system in the borehole is bigger than that in the complete hole. However, it is smaller than the suction pressure of the drainage system and exerts limited effect on gas drainage. As the borehole collapse deteriorates, the effective drainage section of the borehole becomes smaller, while the suction pressure loss in the borehole increases continuously; thus, the gas drainage effect continuously worsens. (3) In case of plug hole, a continuous medium forms between the plug segment coal body and the surrounding coal seam, the plug segment drainage pressure turns into coal-bed gas pressure, and effective drainage length of the borehole shortens, seriously affecting the gas drainage effect. The study carries important theoretical guiding significance for improving gas drainage effect and effectively preventing gas disasters.

scholarly journals The Drainage Horizon Determination of High Directional Long Borehole and Gas Control Effect Analysis

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Yuqi Shang ◽  
Guiyi Wu ◽  
Qinzhi Liu ◽  
Dezhong Kong ◽  
Qiang Li
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Gas Extraction ◽  
Control Effect ◽  
Coverage Area ◽  
Gas Concentration ◽  
Fracture Evolution ◽  
Geological Conditions ◽  
Field Practice ◽  
Gas Control

In order to effectively solve the problem of gas concentration overrun in the upper corner of goaf and tailentry during the mining of panel 9303 in Anshun Coal Mine, based on the advantages of controllable trajectory and wide coverage area of directional drilling technology, high directional long boreholes are arranged in tailentry 9303 to extract pressure relief gas. Firstly, the principle of high directional long borehole drainage technology is introduced, and the fracture evolution of overlying strata is obtained through using numerical simulation, theoretical calculation, and field practice, and the fracture evolution range is determined to be 6–12.69 m, and rationality of fracture height obtained by theoretical analysis and numerical simulation is verified by the method of field borehole peep observation. Through the analysis, it is concluded that the best location of the final hole is within the range of 6–12.69 m of the roof of coal seam 9#. The field practice has proved that the final hole position of the high directional long borehole is arranged at 12 m from the roof of coal seam 9#, and the average gas extraction concentration can reach 40%–50% after the borehole enters the stable extraction stage, the purity of gas extraction is up to 8.5 m3/min, and the gas concentration in the upper corner of panel 9303 is stable below 0.5% during mining, which achieves good gas drainage and control effect and provides a new way for gas control under similar geological conditions.

Numerical Analysis on Drainage Parameters in a High Drainage Roadway

2015 ◽  
Vol 730 ◽  
pp. 122-125
Author(s):  
Yong Sheng Yan ◽  
Jing Zhao Zhang ◽  
Hong Gang Wang ◽  
Zhen Guo Yan
Keyword(s):  
Numerical Analysis ◽  
Air Velocity ◽  
Gas Drainage ◽  
Gas Concentration ◽  
Numerical Tests ◽  
Obvious Change ◽  
Gas Control ◽  
The Right ◽  
Drainage Ratio

The numerical tests of the optimized drainage parameters in a high drainage roadway were conducted with different inlet air velocities, drainage ratios and integrity lengths. The results show that the upper corner's gas concentration decreases gradually with the inlet air velocity and drainage ratio increasing, while there have not obvious change with the Different Integrity Lengthss. Considering from the gas control and gas drainage, the reasonable inlet air velocity is 1-1.25m/s and the right drainage ratio is about 0.3.

scholarly journals Case studies of comprehensive gas control method during fully mechanized caving of low permeability ultra-thick coal seams

2020 ◽  
Author(s):  
Bangyou Jiang ◽  
Shitan Gu ◽  
Yunliang Tan ◽  
Guangchao Zhang ◽  
Jihua Zhang
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
High Efficiency ◽  
Control Method ◽  
Measurement Data ◽  
Low Permeability ◽  
Coal Seams ◽  
Gas Concentration ◽  
High Position ◽  
Gas Control

Abstract Slicing fully mechanized caving mining now is a common high-efficiency mining method for ultra-thick coal seams. However, effective gas control has remained a difficulty in fully mechanized top-coal caving mining of low permeability ultra-thick coal seams. This study focused on mining of the #9-15 coal in Liuhuanggou Coal Mine, Xinjiang Province, China, and combined theoretical analyses and field test results for exploring comprehensive gas control methods for fully mechanized caving of low permeability ultra-thick coal seams. The No. (9-15)06 panel is a top slicing panel of the #9-15 coal with a mining height of 9 m, and the No. (4-5)02 goaf is located on the top of the panel. Through analysis, gas emissions in the No. (9-15)06 panel were mainly sourced from the coal wall, caving of top coal, goaf, and neighboring coal seams. A comprehensive gas control method based on source separation was proposed, which combined gas pre-drainage along the coal seam, high-position drilling on the top, pre-burial of pipes in the goaf, and pressure-balancing ventilation. Considering the poor gas pre-drainage effect for low permeability coal seams, the permeability of the coal seam was enhanced using hydraulic fracturing. According to coal seam and crustal stress distribution characteristics, the arrangement of the boreholes and backward segmented fracturing technology were designed. Field data show that coal underwent remarkable pre-fracturing under hydraulic fracturing. Mean gas pre-drainage from the boreholes was enhanced by nearly 4 times compared to the pre-hydraulic fracturing state. Finally, using the proposed comprehensive control method based on the gas sources, field tests were performed in the No. (9-15)06 panel. Field measurement data demonstrate that gas concentration in the return airflow fluctuated within a range of 0.05%~0.35%, i.e., gas concentration did not exceed the standard. The proposed gas control method can provide insightful reference for the other similar projects.

scholarly journals Research on the Effective Influence Radius of Hydraulic Reaming in Mining Seam

2015 ◽  
Vol 8 (1) ◽  
pp. 161-167
Author(s):  
Li Peng ◽  
Wang Kai ◽  
Li Bo ◽  
Jiang Yifeng ◽  
Gou Jianqiang
Keyword(s):  
Gas Flow ◽  
Coupling Model ◽  
Field Investigation ◽  
Coal Mass ◽  
Gas Content ◽  
Coal Seams ◽  
Gas Drainage ◽  
Permeability Increase ◽  
Influence Radius ◽  
Drainage Effect

In Accordance with the present situations suggesting that the construction of the gas drainage boreholes in mining seam is sufficient and the gas drainage effect in low permeability coal seams does not yield perfectly, the hydraulic reaming technology in mining seam was proposed to increase the gas drainage efficiency. Through the gas flow method, the effective influence radius of hydraulic reaming was determined and the fluid-solid coupling model of gas drainage along boreholes after hydraulic reaming was established theoretically. Following this, the changes in the laws of gas content around the boreholes in the coal seam were simulated and analyzed. The results indicated that hydraulic reaming can effectively promote the stress-relief and permeability-increase of the coal mass around the boreholes, and the coal mass around the reaming boreholes can be divided into gas flow increase zone, gas flow delay attenuation zone and fast decay zone. The effective influence radius of hydraulic reaming was 5.5~6 m. The obtained simulation results were basically in accordance with the field investigation.

scholarly journals An integrated drilling, protection and sealing technology for improving the gas drainage effect in soft coal seams

2020 ◽  
Vol 6 ◽  
pp. 2030-2043
Author(s):  
Hong Li ◽  
Wei Wang ◽  
Yanwei Liu ◽  
Jinkui Ma ◽  
Hong Gao
Keyword(s):  
Coal Seams ◽  
Gas Drainage ◽  
Soft Coal ◽  
Drainage Effect

scholarly journals Research on Optimization of Key Areas of Drainage Borehole Sealing in Ultrathick Coal Seam

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Xin Guo ◽  
Sheng Xue ◽  
Yaobin Li ◽  
Chunshan Zheng ◽  
Linfang Xie
Keyword(s):  
Test Scheme ◽  
Actual Situation ◽  
Air Leakage ◽  
Gas Drainage ◽  
Gas Concentration ◽  
Gas Leakage ◽  
Important Means ◽  
M 12 ◽  
Drainage Effect ◽  
Drainage Borehole

Gas drainage is an important means of gas control. The influence of the key position of the sealing hole on gas drainage was studied by theoretical and numerical simulation combined with field measurement to solve low gas concentration in gas predrainage boreholes in coal mines of China. By analyzing the distribution of cracks around the boreholes and the law of air leakage and simulating the drainage effect of different sealing areas (8 m, 12 m, and 16 m), it was proposed that the key position of the sealing hole should be in the prepeak stress concentration area. According to the actual situation of Baode Mine, the sealing test scheme of different sealing areas was put forward, and the field test was carried out to obtain the key sealing area of gas predrainage boreholes in Baode Mine. Research shows that when the sealing area is 8–16 m, the average gas concentration is 63.57%, and the average pure gas flux is 0.408 m3/min. The sealing effect of this area is better, with fewer cracks, than that of the existing sealing area, effectively preventing gas leakage and increasing the gas concentration and gas scalar.

Labor safety and control of the working area state in the penals while mining steep coal seams by shield aggregates

2020 ◽  
pp. 47-64
Author(s):  
V.V. Zberovskyi ◽  
◽  
R.А. Ahaiev ◽  
K.K. Sofiiskyi ◽  
B.М. Dehlin ◽  
...  
Keyword(s):  
Coal Seam ◽  
Physical And Mechanical Properties ◽  
Dynamic State ◽  
Coal Seams ◽  
Gas Dynamic ◽  
Geological Conditions ◽  
Labor Safety ◽  
Sudden Outburst ◽  
District Change ◽  
And Control

In this article, circumstances and factors which can lead to a degraded labour protection and occurrence of emergency in a district are reviewed and analyzed on the example of an accident occurred at sudden coal-and-gas outburst in the panel face № 42-1146 m of the Tovstyi-Zakhid seam m3 in the Central Mine of the Toretsvukhillia Mining Company. In this article, state of equipment and its location in the district in accordance with the requirements of the safety rules, records of devices which monitor gas-dynamic state of the coal seam and operation of the shield aggregate are considered. Mining and geological conditions of the seam bedding and technological conditions of the district location within the working horizon; methane content in the air of the roadways in the district; change of coal physical and mechanical properties in the area of possible geological disturbance; results of control of the coal seam gas-dynamic state analyzed by acoustic emission parameters; and other risk factors that led to emergencies were studied. The decisions made for controlling possible area with geological disturbance impact which was detected in the horizons of 916 m and 1026 m on the basis of mining-graphic materials and data of geological study in the mining roadways adjacent to the panel No. 14 in the district 42-1146 m were analyzed. The order and sequence of the works established for eliminating consequences of the coal and gas sudden outburst and detecting zone with disturbed coal and outburst cavity were considered. On the basis of the results obtained, conclusions were made and actions were elaborated on preventing accidents at mining steep prone-to-outburst coal seams by the shield aggregates. It is recommended to continue the scientific research for the purpose of detecting zone with possible impact of discontinuous geological disturbance and plicate disturbed zones in the coal seams by the changed hardness of coal in the adjacent panel, and developing certain local measures on preventing gas-dynamic phenomena at mining steep prone-to-outburst seams by the shield aggregates. The objective of this work was to analyze state of the working area and labor protection and to study the conditions and factors which had led to the accident with serious consequences and emergency condition of the panel.

Gas Control Technology under Unstable Disturbance Stress

2015 ◽  
Vol 15 ◽  
pp. 26-34
Author(s):  
Wei Min Cheng ◽  
Lu Lu Sun ◽  
Gang Wang ◽  
Hong Yuan Qu
Keyword(s):  
Control Technology ◽  
Static Loads ◽  
Gas Drainage ◽  
Gas Concentration ◽  
Pressure Step ◽  
Working Face ◽  
Gas Control ◽  
High Level ◽  
Roadway Deformation ◽  
Surrounding Rock Deformation

Under the action of unstable disturbance stress, the stress concentration and roadway deformation are serious when tunneling along the goaf with small pillar while the adjacent working face is mining. This leads to the abnormal gas discharge and the increase of gas emission, and the effectiveness of gas drainage is reduced. In order to eliminate the threat of gas, the dynamic gas control technology of tunneling along the goaf with small pillar under unstable disturbance stress has been researched. The main sources of loads are confirmed by the analysis of dynamic and static loads. Combined with the force analysis of roadway and pillar, the stress superposition level is affected by the relative location of heading face and working face, and the regional characteristics. The measured surrounding rock deformation of A4007 return roadway heading face fits the theoretical analysis and pressure step of working face. The dynamic gas control technology is researched from the aspects of air volume, high-level gas drainage and goaf drainage, and applied in A4007 working face. The gas has been well controlled with the gas concentration of top corner of 0.62% and gas concentration of return current of 0.35%. As a result of the flow control, the gas drainage has not casused spontaneous combustion.

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