Experimental Study on Deep Borehole Pre-Cracking Blasting of Drilling through Strata at Low Permeability Seam

2013 ◽  
Vol 868 ◽  
pp. 339-342
Author(s):  
Jian Liu ◽  
Qian Le
Keyword(s):  
Coal Seam ◽  
Control Area ◽  
Low Permeability ◽  
Gas Extraction ◽  
Test Results ◽  
Deep Borehole ◽  
Coal Seam Gas ◽  
Gas Concentration ◽  
Working Face ◽  
Outburst Coal Seam

In the process of roadway excavation in the low permeability outburst coal seam, with drilling through strata in the bottom drainage roadway extracting coal seam gas of control area. In order to improve extraction effect, the method that deep borehole pre-cracking blasting is used to increase the permeability of coal in the drilling through strata seam segment is proposed. The calculation formula on crushing circle and crack circle radius of deep borehole pre-cracking blasting are derived, and the effective loosening radius of blasting is calculated in theory, the research achievements are applied to field test, the test results show that deep borehole pre-cracking blasting permeability improvement technology is carried out in the drilling through strata of the low permeability outburst coal seam, the permeability of coal seam is improved by 180 times, the gas extraction scalar is raised by 8-10 tomes, during the process of roadway excavation, gas concentration of the working face is 0.2%-0.3%, and tunneling footage is increased by 2 times.

Study on Methods of Exploring the Loosening Radius of Deep-Hole Controlling Blasting

2013 ◽  
Vol 734-737 ◽  
pp. 650-655
Author(s):  
Wen Qing Zhang ◽  
Jian Liu
Keyword(s):  
Theoretical Analysis ◽  
Coal Seam ◽  
Gas Flow ◽  
Critical Factor ◽  
Field Investigation ◽  
Flow Index ◽  
Low Permeability ◽  
Deep Hole ◽  
Deep Borehole ◽  
Outburst Coal Seam

Deep borehole controlling blasting is one of the most popular methods which used to improve permeability of low permeability and highly gassy coal seam. Proper interval between blasting hole is the critical factor. On this paper, the theory and insufficiency of each method are discussed by theoretical analysis and field investigation. The result shows that, because of the complexity of outburst coal seam, the measuring result got by different methods is relative and declinational. We need to make a right choice according to the actual demand. And the method of gas flow index is quickly, visual and reliable, which to be worth paying the utmost attention to.

Dynamic Disaster Forecasting Technology of the Island Working Face in Outburst Coal Seam

2014 ◽  
Vol 962-965 ◽  
pp. 914-918
Author(s):  
Rong Xi Shen ◽  
En Yuan Wang ◽  
Shao Bin Hu ◽  
Jun Jun Feng
Keyword(s):  
Coal Seam ◽  
Electromagnetic Radiation ◽  
Gas Content ◽  
Ratio Method ◽  
Safety Level ◽  
Gas Concentration ◽  
Working Face ◽  
Dynamic Disaster ◽  
Outburst Coal Seam ◽  
Hydraulic Supports

Coal and gas outburst and rock burst are the main threats of the island working face in outburst coal seam. According to the characteristic of No. 11061 island face in outburst coal seam, Liangbei coal mine, China, the dynamic disaster mechanism of island working face in outburst coal seam was analyzed. Based on the monitor of gas concentration and electromagnetic radiation and hydraulic supports resistance in the 11061 island face, the comprehensive forecasting technology of the island face in outburst coal seam was built, then the critical values of gas concentration and electromagnetic radiation and hydraulic supports resistance are calculated by three-ratio method. Finally, the comprehensive forecasting technology is used in the island working face. The results show that the combined action of gas content and stress induces the dynamic disaster of the island working face in outburst coal seam, and the comprehensive forecasting technology can forecast accurately dynamic disaster in the 11061 island face, which has brought successful engineering experience and distinct economic benefit. It can improve significantly the mine production safety level to research the forecasting technology of the island working face in outburst coal seam.

scholarly journals Stress Distribution and Gas Concentration Evolution during Protective Coal Seam Mining

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Xingang Niu ◽  
Biming Shi ◽  
Zhigang Zhang ◽  
Yongjiang Zhang
Keyword(s):  
Numerical Modelling ◽  
Coal Seam ◽  
Mining Method ◽  
Coal Seam Gas ◽  
Gas Concentration ◽  
Induced Stress ◽  
Complete Extraction ◽  
Stress Zone ◽  
Seam Mining ◽  
Concentration Evolution

Coal and gas burst is one of the significant and catastrophic hazards in underground longwall operations. To date, the protective coal seam mining has been recognized as the most effective mining method for minimizing or even avoiding the effect of the coal and gas burst. In this paper, numerical modelling and field test were carried out for the longwall operation in Qidong Coal Mine in order to investigate the induced stress and coal seam gas drainage performance in the protected coal seam after the complete extraction of the protective coal seam. It was found that four stress zones can be classified in the protected coal seam being the original stress zone, stress concentration zone, stress relief zone, and recompaction zone. In addition, the monitoring data of gas concentration and volume change in the field agree well with the numerical modelling results.

scholarly journals Analysis of pressure relief and outburst prevention effect and mining depth effect of floor roadway in single serious outburst coal seam

2021 ◽  
Vol 267 ◽  
pp. 01051
Author(s):  
Guohong Chen
Keyword(s):  
Coal Seam ◽  
Field Test ◽  
Surrounding Rock ◽  
Test Results ◽  
Pressure Relief ◽  
Depth Effect ◽  
Mining Depth ◽  
Geological Conditions ◽  
Ground Stress ◽  
Outburst Coal Seam

In order to solve the serious problem of single serious outburst coal seam gas disaster, based on the gas geological conditions of Jiangxi Fengcheng Qujiang company, theoretical analysis, numerical simulation, field test and other comprehensive research methods were used to analyze the partition fracture law of roadway surrounding rock under different mining depth conditions. The results show that: under the conditions of high ground stress, high temperature and other environmental conditions, the radius of pressure relief loose circle of surrounding rock of roadway is significantly increased, and it is significantly larger than that of shallow part. In the deep area of - 800m elevation, the distance between floor roadway and coal seam is optimized to be 12 ~ 15m. The field test results show that the original permeability coefficient of overlying coal seam of floor roadway increases by 55.74 times, and the pressure relief effect is good.

scholarly journals Reasonable Layout of High Drainage Roadways for Jiaojiazhai Mine

2022 ◽  
Author(s):  
Dongjie Hu ◽  
Zongxiang Li
Keyword(s):  
Control Program ◽  
Simulation Software ◽  
Fluid Simulation ◽  
Gas Extraction ◽  
Tracer Gas ◽  
Element Analysis ◽  
Gas Concentration ◽  
Working Face ◽  
Deformation Law ◽  
Better Than

Abstract To ensure that the gas concentration at the top corner does not exceed the limit, a reasonable level of the high drainage roadway layout in Jiaojiazhai Mine should be determined. In this work, based on the actual conditions of the working face, an SF6 tracer gas was used to test the connectivity between the high drainage roadway and the working face. A discrete element analysis program was used to simulate the deformation law of the overlying strata in the goaf, and a corresponding caving control program for the surrounding rock was written based on the obtained parameters and “O” ring theory. A fluid simulation software was used to simulate and analyze five goaf models with different high drainage roadway layouts (10, 15, 20, 25, and 30 m). The gas drainage data for two layers (10 m and 20 m) of the high drainage roadway were measured. The results showed that the height of the caving zone in the goaf is approximately 20 m, and when the high drainage roadway is arranged along the roof (when the layout layer height is 10 m), the roadway will be directly connected to the working face, thus pumping fresh air to the working face. The gas extraction effect of the 20 m stratum was better than those of the other strata. The simulation results of the gas extraction were consistent with the measured data. The proposed scheme was practically applied, and its effect was found to be evident, thus solving the problem of high gas concentration at the top corner and increasing the mine output.

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.

scholarly journals Dynamic Secondary Borehole-Sealing Method for Gas Drainage Boreholes along the Coal Seam

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Wei Qin ◽  
Jialin Xu
Keyword(s):  
Abutment Pressure ◽  
High Water ◽  
Test Results ◽  
Gas Drainage ◽  
Gas Concentration ◽  
Working Face ◽  
Opportune Time ◽  
Sealing Device ◽  
Better Than

Under the influence of advanced abutment pressure, the tightness of a borehole is destroyed, so secondary borehole sealing is needed; however, the opportune time for a secondary borehole sealing is unclear. In addition, current borehole-sealing devices do not have a secondary borehole-sealing functionality. In this paper, an opportunity election model of secondary borehole sealing was established, and a dynamic secondary borehole-sealing device was developed. In working face 3908 of the Kaiyuan Coal Mine, an in situ dynamic secondary borehole-sealing test was conducted. The test results show that the tightness of the boreholes sealed with high-water-expansion slurry is obviously better than that of the boreholes sealed with cement mortar and polyurethane. When a borehole is destroyed by the peak of the advanced abutment pressure, the secondary borehole-sealing measures can significantly improve borehole suction pressure, gas concentration, and gas drainage amount in the advanced abutment pressure loading stage.

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