The Effect Evaluation of Removing Outburst through Bedding and Layer-through Boreholes Combined Gas Drainage

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.256-259.366 ◽

2012 ◽

Vol 256-259 ◽

pp. 366-371

Author(s):

Zhong Ming Zhao ◽

Lei Wang ◽

Jian Bang Wu

Keyword(s):

Gas Pressure ◽

Gas Content ◽

Effect Evaluation ◽

Prevention Measures ◽

Gas Drainage ◽

Residual Gas ◽

Favorable Conditions

In order to test the validity of regional outburst prevention measures that combined the bedding boreholes and layer-through boreholes in 3104 coalface, according to the relevant provisions, used drilling index, pre-pumping index and gas index to evaluate the effect of removing outburst in 3104 coalface. The evaluation results shown that through the pre-pumping gas, the rate of pre-pumping gas was 53.7%, more than 30%; residual gas content was 2.85～5.07m3/t, less than 8m3/t; residual gas pressure was 0.01～0.02MPa, less than 0.74 MPa. Therefore, the coalface has eliminated the danger of outburst and created favorable conditions for safety mining.

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The Relationship between Mining-Induced Stress and Coal Gas under an Optimized Support Scheme: A Case Study in the Guanyinshan Coal Mine, China

Geofluids ◽

10.1155/2021/2421398 ◽

2021 ◽

Vol 2021 ◽

pp. 1-17

Author(s):

Tianjun Zhang ◽

Jiaokun Wu ◽

Yong Chen ◽

Hong Ding ◽

Hongyu Ma ◽

...

Keyword(s):

Gas Pressure ◽

Gas Content ◽

Rock Support ◽

Drill Cuttings ◽

Coal Gas ◽

Gas Desorption ◽

Induced Stress ◽

Coal And Gas Outbursts ◽

Residual Gas ◽

The Relationship

Stress is one of the main factors influencing coal and gas outbursts. The apparent effects of the crustal stress, the structural stress, and the mining-induced stress increase as the depth of mining increases. At present, there have been few studies of the relationship between the comprehensive analyses of the crustal stress, mining-induced stress, and coal gas. The in situ measurement of the relationship between stress-related behaviors and coal gas under the influence of mining was conducted through experimental analysis of surrounding rock support and coal and gas outburst control and optimization of surrounding rock support materials and system construction. The results showed that the mining-induced stress first increased to a peak value, then gradually decreased, and tended to stabilize as the footage progresses. Stress appears at 96 m ahead due to mining; after 57 m of advancing, there is a large increase until it passes through this area. The stress in front of the working face increases linearly, and the increase range is obviously larger than that of the coal body in a certain range on both sides. The support anchoring force gradually decreased and tended to be stable after rapidly increasing to a maximum value. The deep displacement of the roof increased linearly and tended to be stable after reaching an accumulated displacement which can reach 16-28 mm. The residual gas pressure in front of mining operations decreased rapidly, and beyond 15 m on each side of the roadway, it decreased significantly. The residual gas pressure and gas content were consistent with the gas desorption index of drill cuttings due to the influences of gas predrainage and mining. The stress along the direction of the roadway and the residual gas content, the residual gas pressure, and the gas desorption index of drill cuttings conform to the logarithmic functional relationship. The research results provide a basis for the comprehensive prevention and control of coal and gas outbursts from multiple angles considering stress, coal, and gas.

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Prediction of Residual Gas Content during Coal Roadway Tunneling Based on Drilling Cuttings Indices and BA-ELM Algorithm

Advances in Civil Engineering ◽

10.1155/2020/1287306 ◽

2020 ◽

Vol 2020 ◽

pp. 1-8

Author(s):

Zhenhua Yang ◽

Hongwei Zhang ◽

Sheng Li ◽

Chaojun Fan

Keyword(s):

Coal Seam ◽

Extreme Learning Machine ◽

Back Propagation ◽

Prediction Method ◽

Gas Content ◽

Percentage Error ◽

Support Vector ◽

Prevention Measures ◽

Residual Gas ◽

Learning Machine

In order to predict the residual gas content in coal seam in front of roadway advancing face accurately and rapidly, an improved prediction method based on both drilling cuttings indices and bat algorithm optimizing extreme learning machine (BA-ELM) was proposed. The test indices of outburst prevention measures (drilling cuttings indices, residual gas content in coal seam) during roadway advancing in Yuecheng coal mine were first analyzed. Then, the correlation between drilling cuttings indices and residual gas content was established, as well as the neural network prediction model based on BA-ELM. Finally, the prediction result of the proposed method was compared with that of back-propagation (BP), support vector machine (SVM), and extreme learning machine (ELM) to verify the accuracy. The results show that the average absolute error, the average absolute percentage error, and the determination coefficient of the proposed prediction method of residual gas content in coal seam are 0.069, 0.012, and 0.981, respectively. This method has higher accuracy than other methods and can effectively reveal the nonlinear relationship between drilling cuttings indices and residual gas content. It has prospective application in the prediction of residual gas content in coal seam.

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Gas Migration Patterns with Different Borehole Sizes in Underground Coal Seams: Numerical Simulations and Field Observations

Minerals ◽

10.3390/min11111254 ◽

2021 ◽

Vol 11 (11) ◽

pp. 1254

Author(s):

Haibo Liu ◽

Zhihang Shu ◽

Yinbin Shi ◽

Xuebing Wang ◽

Xucheng Xiao ◽

...

Keyword(s):

Gas Flow ◽

Gas Content ◽

Gas Migration ◽

Coal Seams ◽

Gas Drainage ◽

Migration Patterns ◽

Gas Recovery ◽

Residual Gas ◽

Simulation Results ◽

Drainage Borehole

Gas flow in a coal seam is a complex process due to the complicated coal structure and the sorption characteristics of coal to adsorbable gas (such as carbon dioxide and methane). It is essential to understand the gas migration patterns for different fields of engineering, such as CBM exploitation, underground coal mine gas drainage, and CO2 geo-sequestration. Many factors influence gas migration patterns. From the surface production wells, the in-seam patterns of gas content cannot be quantified, and it is difficult to predict the total gas production time. In order to understand the gas flow patterns during gas recovery and the gas content variations with respect to production time, a solid-fluid coupled gas migration model is proposed to illustrate the gas flow in a coal seam. Field data was collected and simulation parameters were obtained. Based on this model, different scenarios with different borehole sizes were simulated for both directional boreholes and normal parallel boreholes in coal seams. Specifically, the borehole sizes for the directional boreholes were 10 m, 15 m, and 20 m. The borehole sizes for the normal parallel boreholes were 2 m, 4 m, and 6 m. Under different gas drainage leading times, the total gas recovery and residual gas contents were quantified. In Longwall Panel 909 of the Wuhushan coal mine, one gas drainage borehole and five 4 m monitoring boreholes were drilled. After six months of monitoring, the residual gas content was obtained and compared with the simulation results. Of the total gas, 61.36% was drained out from the first 4 m borehole. In this field study, the effective drainage diameter of the drainage borehole was less than 8 m after six months of drainage. The gas drainage performance was tightly affected by the borehole size and the gas drainage time. It was determined that the field observations were in line with the simulation results. The findings of this study can provide field data for similar conditions.

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Residual gas pressure in 200 W-CW magnetron made of commercial E copper of 99.9 purity (continuous vertical cast)

Vacuum ◽

10.1016/0042-207x(63)91989-4 ◽

1963 ◽

Vol 13 (9) ◽

pp. 387

Keyword(s):

Gas Pressure ◽

Residual Gas

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Very Thick Coherently Strained GexSi1−x Layers Grown in a Narrow Temperature Window

MRS Proceedings ◽

10.1557/proc-220-175 ◽

1991 ◽

Vol 220 ◽

Cited By ~ 5

Author(s):

C. H. Chern ◽

K. L. Wang ◽

G. Bai ◽

M. -A. Nicolet

Keyword(s):

Growth Temperature ◽

Strain Relaxation ◽

Gas Pressure ◽

High Density ◽

Misfit Dislocations ◽

High Quality ◽

Strained Layers ◽

Temperature Window ◽

Residual Gas

ABSTRACTStrain relaxation of GexSi1−x layers is studied as a function of growth temperature. Extremely thick coherently strained layers whose thicknesses exceed more than fifty times of the critical thicknesses predicted by Matthews and Blakeslee's model were successfully grown by MBE. There exits a narrow temperature window from 310 °C to 350 °C for growing this kind of high quality thick strained layers. Below this temperature window, the layers are poor in quality as indicated from RHEED patterns. Above this window, the strain of the layers relaxes very fast accompanied with a high density of misfit dislocations as the growth temperature increases. Moreover, for samples grown in this temperature window, the strain relaxation shows a dependence of the residual gas pressure, which has never been reported before.

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Permeability Enhancement Properties of High-Pressure Abrasive Water Jet Flushing and Its Application in a Soft Coal Seam

Frontiers in Energy Research ◽

10.3389/fenrg.2021.679623 ◽

2021 ◽

Vol 9 ◽

Author(s):

Xinzhe Zhang ◽

Piotr Wiśniewski ◽

Sławomir Dykas ◽

Guojie Zhang

Keyword(s):

High Pressure ◽

Coal Seam ◽

Water Jet ◽

Gas Pressure ◽

Theory And Practice ◽

Abrasive Water Jet ◽

Gas Drainage ◽

Permeability Enhancement ◽

Soft Coal ◽

Soft Coal Seam

High-pressure abrasive water jet flushing (HPAWJF) is an effective method used to improve coal seam permeability. In this study, based on the theories of gas flow and coal deformation, a coupled gas-rock model is established to investigate realistic failure processes by introducing equations for the evolution of mesoscopic element damage along with coal mass deformation. Numerical simulation of the failure and pressure relief processes is carried out under different coal seam permeability and flushing length conditions. Distributions of the seepage and gas pressure fields of the realistic failure process are analyzed. The effects of flushing permeability enhancement in a soft coal seam on the gas drainage from boreholes are revealed by conducting a field experiment. Conclusions can be extracted that the gas pressure of the slotted soft coal seam is reduced and that the gas drainage volume is three times higher than that of a conventional borehole. Field tests demonstrate that the gas drainage effect of the soft coal seam is significantly improved and that tunneling speed is nearly doubled. The results obtained from this study can provide guidance to gas drainage in soft coal seams regarding the theory and practice application of the HPAWJF method.

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