Prediction method for risks of coal and gas outbursts based on spatial chaos theory using gas desorption index of drill cuttings

2011 ◽  
Vol 21 (3) ◽  
pp. 439-443 ◽  
Author(s):  
Dingqi Li ◽  
Yuanping Cheng ◽  
Lei Wang ◽  
Haifeng Wang ◽  
Liang Wang ◽  
...  
Keyword(s):  
Chaos Theory ◽  
Prediction Method ◽  
Drill Cuttings ◽  
Gas Desorption ◽  
Spatial Chaos ◽  
Coal And Gas Outbursts

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

Geofluids ◽  
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.

scholarly journals A New Method for Predicting Coal and Gas Outbursts

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Guowei Dong ◽  
Xuanming Liang ◽  
Qixiang Wang
Keyword(s):  
Prediction Method ◽  
Coal Mass ◽  
New Method ◽  
Gas Content ◽  
Good Prediction ◽  
Soft Layer ◽  
Gas Desorption ◽  
Coal And Gas Outbursts ◽  
Gas Pressures

In view of the fact that coal and gas outbursts are difficult to predict, a new method for predicting coal and gas outbursts was proposed based on occurrence mechanisms of coal and gas outbursts relating to coal mass strength, gas pressure, and in situ stress. The method revealed that the rate of occurrence of coal and gas outbursts in mines was 5% to 10% and gas pressures for coal and gas outbursts in shallow and deep mines in China were greater than 0.74 and 0.6 MPa, respectively. The prediction index for coal and gas outbursts based on the gas factor was the gas desorption index of drilling cuttings (K1), which is referred to the gas content desorbed from the coal mass in the first minute of drilling. The prediction index for coal and gas outbursts based on coal mass strength was the thickness of a soft layer that could be twisted into powder by hand. Based on many cases of coal and gas outbursts, the critical thickness of the soft layer was found to have been 0.2 m. The prediction index for coal and gas outbursts based on in situ stress was the weight of drilling cuttings, which represented the mass of drilling cuttings per linear metre of boreholes with diameters of 42 or 75 mm. Finally, the new prediction method and prediction index critical values for coal and gas outbursts were verified based on industrial application tests. This method has been widely applied on-site and obtained good prediction results.

scholarly journals Pulverization characteristics of coal affected by magmatic intrusion and analysis of the abnormal gas desorption index on drill cuttings

2017 ◽  
Vol 36 (1-2) ◽  
pp. 805-829 ◽  
Author(s):  
Er-Tao Chen ◽  
Liang Wang ◽  
Yuan-Ping Cheng ◽  
Hai-Jun Guo ◽  
Cong-Meng Hao ◽  
...  
Keyword(s):  
Particle Size ◽  
Coal Seam ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Total Pore Volume ◽  
Tectonic Stress ◽  
Drill Cuttings ◽  
Magmatic Intrusion ◽  
Gas Desorption

The gas desorption index of drill cuttings is a basic index that measures the initial desorption capacities of coal seams and predicts coal seam gas outbursts. Following a long period of gas drainage in the No.7 coal seam of the No.86 mining area in the Haizi coal mine, the gas desorption index of drill cuttings was still found to be much higher than the threshold value for outburst risks. This abnormal phenomenon led to the present study of the rational selection of test methods and objects in this context. In this study, particle size distribution, pore structure and gas desorption characteristics of coal samples in anomalous areas were analyzed. We found that desorption characteristics are related to particle size and particle size varies in relation to tectonic stress and magmatic intrusions. It appears that the anomalous readings are related to particle size of the coal, resulting from tectonic/magmatic pulverization. Furthermore, measured particle size of drill cuttings is not actually reflective of coal particle size – larger particles may be comprised of multiple smaller particles. The results show that coal samples with particle size <1 mm accounts for 76.3% of total samples and coal samples with particle size >1 mm only accounts for 23.7% of total samples. The porosity and total pore volume increase as the particle size decreases. The specific surface area increases with decreasing pore diameter. Transitional pores and micropores increase the specific surface area of the coal sample considerably. The desorption capacity increases with decreasing particle size. The additional tectonic stress caused by magmatic intrusion has a crushing effect, and 1–3 mm particles used in test were composed of a large amount of smaller particles, eventually resulting in abnormal gas desorption index phenomena. Therefore, we proposed an improved method for measuring the gas desorption index of pulverized coal.

Gas desorption index of drill cuttings affected by magmatic sills for predicting outbursts in coal seams

2015 ◽  
Vol 9 (1) ◽  
Author(s):  
Long-biao Cheng ◽  
Liang Wang ◽  
Yuan-ping Cheng ◽  
Kan Jin ◽  
Wei Zhao ◽  
...  
Keyword(s):  
Coal Seams ◽  
Drill Cuttings ◽  
Gas Desorption
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