Gas Overrun Research Articles

Case Study on the Mechanism of Influence of Stoppage on Ground Pressure under Different Rates of Advance

Because of daily maintenance, equipment damage, gas overrun, and other force majeure factors, the continuous stopping of the working face causes the roof pressure to accumulate, which leads to causing accidents such as coal wall spalling and roof falling. To address the roof safety problem caused by continuous stoppages, the 620 working face in the Huangling mining area is taken as the research object. Through field measurement, theoretical analysis, numerical simulation, and other research methods, the influence and mechanism of stopping pressure under different rates of advance are studied. The results show that the velocity factor of roof load transfer is positively correlated with the advancing velocity of the working face; the reasonable length of the suspended roof is mainly affected by the number of caving holes and the effect of pressure relief; and comparing the two stages of advance speed of 4.8 m/d and 12.8 m/d, the periodic weighting step distance of the latter increases by 24.4% compared with the former, and the rate of increase of support load caused by stopping mining increases by 42.1% compared with the former. The roof pressure accumulation caused by stopping mining is increased. Taking appropriate measures for local forced caving of the working face can release the roof pressure and reduce the risk of local caving of the working face. The study can provide a theoretical basis for roof control of continuous stopping under similar engineering conditions.

Study on Response Characteristics of Surrounding Rock Rupture Microseismic Events during Coal Roadway Excavation

In order to solve the problems such as coal burst and abnormal gas overrun caused by the fracture of surrounding rock in the process of mining in the coal roadway, the ESG microseismic monitoring system is built on the driving face of 8005 transportation roadway of Wuyang Coal Mine to carry out a real-time, continuous, and omnidirectional dynamic state monitoring. In this way, the characteristics of time-frequency evolution and energy distribution of the acquired signals are systematically analyzed, and the location of the roadway microseismic events is studied. The results show the following: (1) influenced by mining activities, the localized microseismic events are mostly distributed in front and on both sides of the working face. Due to mining activities and geological changes, the equilibrium of original stress in coal and rock mass is broken. The stress thus is released accompanied by fracture before reaching a new equilibrium. (2) By comparing the coal and rock fracture signals with the interference signals, it is found that the fracture signals have short duration and large amplitude with obvious abrupt change characteristics. The interference signals have long duration and relatively small amplitude with less obvious change. (3) Fourier transform analysis shows that the main frequency of coal rock fracture signals is 100–200 Hz with large total energy concentrated in the first frequency band, while that of interference signals is mostly less than 100 Hz with small total energy. The research results can effectively identify the coal and rock dynamic disasters, provide technical support for the prediction and early warning of hidden danger, and guide the safe and efficient production.

Influence of hard-roof on gas accumulation in overlying strata: A case study

Protective seam mining is one of the most commonly used technique to realize stress relief and permeability enhancement of reservoirs, so as to improve gas drainage efficiency. However, for coal reservoir with a hard roof, such as the tight sandstone, magmatic rocks, the distribution and evolution of destressed zone and gas field have not been fully understood, which leads to an inefficient gas control in the field. In this work, taking the geological background of Pingmei 12th Coal Mine as an example, we numerically investigated the evolution and distribution of stress, permeability and gas field in the hard-roof stope during protective seam mining. The results show that in the zone with a distance greater than 3.7 m, stress in the hard-roof stope is significantly higher than that in the conventional stope and the permeability enhancement ratio in the hard-roof stope is significantly lower than that in the conventional stope. In the overlying strata, the existence of the hard roof inhibits the upward extension of the fractured zone, and the range of the fractured zone in the hard-roof stope is obviously smaller than that in the conventional stope. Therefore, in the hard-roof stope, the relieved gas accumulates in the gob, instead of entering the overlying fractured zone, which may put a threat to the mining safety. To solve this problem, the presplitting blasting technique was applied to cut the hard roof. After the collapse of the hard roof, the overlying fractured zone is fully developed, and the gas accumulated in the gob enters the fractured zone driven by the concentration difference and buoyancy. This can not only prevent gas overrun, but improve gas drainage efficiency of the upward borehole. This practice could be used as a valuable example for other coal mines with similar geological conditions.

Differential Gas Drainage Technology for Upper Corner of Working Face by High Position Directional Long Borehole

In the mining process of high gas mining area, the gas emission from goaf is large, which leads to the gas overrun in the upper corner of the working face, and affects the safe mining of the mine. This paper studies the differential drainage of the upper corner gas by high-level directional long borehole, and then solves the problem of gas control in the upper corner. Taking a fully mechanized mining face as the research object, this paper analyzes the theoretical parameters of the overlying strata failure of the working face, and according to the production practice, the high position directional long drilling layer is arranged differently, and the influence of high position directional drilling on gas drainage effect in different layers is analyzed, and the best location in different distance and height area is obtained to guide the actual production work. The research results show that the differential drainage method of high position directional long borehole can effectively control the gas overrun in upper corner of fully mechanized mining face in thick coal seam.

Research and application of gas overrun prevention technology by hydraulic reaming

In order to solve the problem of gas overrun in hydraulic reaming of coal mine, this research has been put forward. Field tests show that, the overrun gas with hydraulic reaming mainly comes from the large amount of gas release caused by the occurrence change, and the sudden release of gas gathered due to the blockage of the drilling, etc. By adjusting the air supply of the area, improving the construction technology, controlling the slag rate, and adopting the blowout preventer, the gas overrun with hydraulic reaming can be effectively controlled.

Gas emission law and control method of working face in extra thick coal seam

Aiming at the problem of abnormal gas emission in fully mechanized caving face during mining, the law of gas emission from coal and rock in front of working face is studied, and the main factors of gas emission from coal wall and goaf are analyzed. This paper puts forward the method of gas drainage by surface drilling, which provides a new way to solve the gas overrun of upper corner, return air roadway and working face under the condition of high-intensity fully mechanized caving mining in extra thick coal seam, which has great engineering significance to ensure the safety and efficient production of the mine.

A comprehensive gas extraction system coupling high-level suction roadway and boreholes for gas disaster prevention in closely-spaced multiple coal seams

ABSTRACT Mining a protective layer is an effective way to prevent coal and gas outbursts in underground coal mines; this method has been used widely. However, when mining closely spaced multiple coal seams (CMCS), gas from adjacent coal seams flows into the working face through fractures in the goaf. This is caused by pressure relief and consequently gas overruns occur, a significant problem that negatively affects efficient mine production. This study analyzes the reasons that gas overruns occur at a working face during the mining of CMCS protective layers. A comprehensive gas extraction system coupling a high-level suction roadway and boreholes was introduced and applied to prevent and control gas overruns at the working face. Gas extraction rates and the amount of gas in the air return system were monitored and the results used to evaluate the effectiveness of the system. The results show that gas desorption caused by pressure relief of the adjacent coal seams was the main cause of the gas overruns at the working face. After the system started working, the average extraction rate increased from 2390 m3/d to 16200 m3/d with average gas concentration in the extracted gas rising from 6% to 41.21%. After using the gas extraction system, the average gas concentrations in the tailgate roadway, working face upper corner, and return airway were reduced by 45%, 30%, and 13%, respectively. Gas overrun accidents have apparently been eliminated. At the time of this writing, there have been no new gas overrun accidents. In addition to solving the gas problem, the gas extraction system has allowed average coal production from the working face to increase 46.7% per month and in 9 months, 4.4 million cubic meters of gas, which could be directly used to generate electricity, was extracted. The tests indicated that an appropriately configured high-level gas extraction system in the fractured zone can effectively solve the working face gas overrun problem in mines exploiting CMCS. This study can be used as a valuable example for other coal deposits being mined under similar geological conditions.

Research on Multi-directional Gas Drainage Technology in Goaf of Working Face

According to the abnormal gas overrun quadrant in the mined-out area during the initial mining and normal mining of a mine, the causes of some gas outbursts were analyzed, and the multi-directional extraction method for low-level drilling, middle-level drilling and high-level drilling was designed and constructed Successively connect and replace the mined-out gas, and the effect analysis shows that each borehole achieves and exceeds the expected effect, which improves the efficiency of gas extraction in the mined-out area and relieves the gas pressure during the normal mining of the working face.

Study on simultaneous extraction of coal and gas and clean utilization in high-gas outburst mines

In order to solve the problem of gas overrun during the mining of large mining height working face in high process mine, based on the gas emission prediction, the source and composition of gas emission are analyzed, gas extraction method of combining the grossmeasures boreholes with borehole along the seam are put forwarded, the reasonable arrangement of the gas extraction parameter are designed, comprehensive control of gas in working face, heading face and goaf was carried out, and the new scheme of high concentration gas and low concentration gas clean utilization is proposed. It has been proved by practice that the coal and gas co-mining and clean utilization scheme of ‘gas pre-extraction + gas civil-oriented + gas power generation + waste heat utilization’ is of great significance to ensure coal mine safety production and environmental protection.

CFD-based optimization of the installation location of the wall-mounted air duct in a fully mechanized excavation face

As a novel ventilation method for fully mechanized excavation face, i.e., wall-mounted air duct, has outstanding advantages in solving the problems of dust pollution and gas overrun. In order to decide the best installation location of the wall-mounted air duct, a physical model was developed proportional to the dimensions of C103 fully mechanized excavation face of the Nahe Coal Mine of the Bai Coal Group in Baise, Guangxi Province. The CFD numerical method was used to analyze the air flow field, dust concentration distribution and gas diffusion of the excavation face when the wall-mounted air duct was installed at different positions. The results showed that the dust and gas control effect in the fully mechanized excavation face was highly dependent on the installation location of the wall-mounted air duct. When the wall-mounted air duct was installed farther away from the working face, on the one hand, the wind curtain moved backward and the dust control effect was poorer; on the other hand, the gas was diffused to a larger distance and the concentration of gas in front of the working face was lower. For the investigated fully mechanized excavation face, the reasonable installation distance of the wall-mounted air duct should be 9.6 m. At this installation distance, the concentration of gas on the working face roof was 0.65%, and the concentration of dusts around the roadheader’s driver was 59 mg/m3.

Gas comprehensive prevention and control technology and practice in outburst mine

In view of the present situation of gas occurrence in Xiaoxi coal industry, combined with the problems of high gas pressure, high content and complex geological structure in the gas control, the comprehensive gas prevention and control technology to meet the mining connection is proposed.It mainly includes the pre drainage measures of underground kilometer drill hole, through layer drilling and bedding drilling, comprehensive gas prevention technology of surface well pre drainage of coal seam gas and underground cross layer drilling area outburst prevention. The practice shows that after the implementation of comprehensive gas control measures, the residual gas content and gas pressure of coal seam are greatly reduced, and the gas control effect is remarkable. Through the comprehensive gas control technology of outburst mine, the gas control level of Xiaoxi coal industry has been significantly improved, and the number of times of gas overrun has decreased year by year.

Research of pressure influence in the gas supply system on the energy consuption level of gas devices

There are investigated the influence of operating pressures in the gas supply system on the level of such energy indicators as efficiency, gas flow and gas overrun by gas equipment in residential buildings. There is established a relationship between the values of operating pressures in the gas supply system and the gas consumption level of household appliances. The causes of insufficient pressure in the gas networks of settlements are analyzed in the article. There is also developed an algorithm for calculating the change in the efficiency of gas appliances depending on the operational parameters of the gas network. It has been found that the most efficient operation of gas appliances is observed at an overpressure at the inlet of gas appliances of about 1200 Pa.To ensure the required quality of natural gas combustion among consumers and minimize gas consumption there are justified the following measures in the article: coordinating a domestic regulatory framework for assessing the quality of natural gas with international norms and standards; improving the preparation of gas coming from local wells before supplying it to gas distribution networks; auditing low pressure gas pipelines and reconstructing areas affected by corrosion; ensuring standard gas pressure in the network for the normal operation of domestic gas appliances; stating quality indicators of natural gas combustion by gas sales organizations.

Research on Stress Distribution and Safe Mining of Lower Layer Working Face Based on Resource Integration

The use of small face mining mode in the upper stratification of Qudi Coal Mine leads to the imbalance of mining succession, in order to improve coal recovery rate and utilization rate, solve the problem of over-limit gas overrun, in the context of resource integration, combine two adjacent working face goafs into one large working face, ensure safe and efficient recovery of the remaining 24m coal pillar, through numerical simulation and on-site measurement, the variation law of stress in lower layer is studied. The results show: ZYP3200/17/28 hydraulic support can fully meet the roof support. Residual gas content and the gas-concentration in air-return laneway indicate that the 31012 mining face has eliminated the outstanding danger, safe, efficient and green mining has been realized.

Design of gas drainage modes based on gas emission rate in a gob: a simulation study

In the process of working face advance in longwall coal mining, a great deal of gas relieved by the strata adjacent to the mining coal seam and the residual coal in gob migrates to gob. If the gas drainage method in gob is unreasonable, gas will accumulate in the upper corner and overrun in the return air flow. In the paper, a CFD (computational fluid mechanics) model of gob based on the actual geological conditions and gas drainage mode of 1262 working face of Dingji Coal Mine, China, was established. The gas drainage modes that should be taken to effectively control gas accumulation in the upper corner and gas overrun in the return air flow at different gas emission rates were discussed. The simulation results show that when the gas emission rate in the working face is lower than 20 m3/min, buried pipe drainage can effectively control gas accumulation in the upper corner and gas overrun in the return air flow. When gas emission rate there is between 20 and 30 m3/min, the two problems can be solved through cross-measure borehole drainage combined with buried pipe drainage. When gas emission rate there is higher than 40 m3/min, they can be effectively controlled through a three-dimensional drainage mode including buried pipes, cross-measure boreholes, and surface wells. Arranging surface wells within the fractured zone near the return airway can increase the gas drainage rate, and the gas concentration can reach over 85%; the gas concentrations of buried pipe drainage and cross-measure borehole drainage are 15~20% and 70~80%, respectively.

Coal Mine Hydraulic Fracturing Underground Drainage Research and Engineering Application

Using elastic mechanics and fracture mechanics, analyzing the coal seam hydraulic fracturing breakdown pressure, given its theoretical formula. According to hydraulic fracturing stress status, given the form of two typical hydraulic fracture morphology. Analyzing hydraulic fracturing highly elliptical shape. The displacement field in plane stress state is given, and the theoretical formula of fracturing radius of hydraulic fracturing is deduced. The fracturing technology of underground fracturing is presented, and the fracturing location and fracturing parameters are determined. In Sihe Coal Mine conducted fracturing test, the test results showed that: the average of drainage volume of fracturing hole improved 4.4 times compared with non-pressed-hole. The extraction compliance time is reduced by 38%. Roadway tunneling speed was improved by 15%. It can solve the problem of gas overrun in roadway excavation well, and has a good application and popularization value.

Gas Control Technology of Fully Mechanized Caving Face of Hard Desorbing Coal Seam

Basing on the problems of residual coal in goaf in fully mechanized caving face in hard desorbing coal seam, high content of residual gas, large gas emission, serious gas overrun in return airflow corner and vitiated air, combing the actual situation in 3-219 fully mechanized caving face, the paper has adopted adjacent goaf drainage, drainage in gas drainage technology, formed a low investment cost and effective gas control technology and ensured the safe and efficient production in coal face and has a certain reference to control gas of fully mechanized caving face in hard desorbing coal seam.

The Application of Gas Drainage Technology in the Workface of "Three Soft" Specially Thick Coal Seam

In order to improve the gas drainage effect of "three soft" coal seam with low-permeability and eliminate the gas overrun in the upper corner and return air during the production process, this paper did an exploration on the comprehensive gas management on the fully mechanized caving face of gassy mines in Xuangang mine area and its application achieved a good result.

Gas Control Technology for Fully Mechanized Face of Outburst Coal Seam with Hard Roof during Initial Caving

In the fully mechanized working face, with working face forward, gob area become bigger and bigger, when the top area reach a certain span ,roof in gob suddenly cave, outspreading a large quantity of mine gas, easy to cause the gas overrun and gas accidents. In addition, shock pressure which is caused when large area roof cave, easily causing casualties and damage of equipment. This paper introduces Pan three Coal mine 17171(1) ore advance of fully mechanized working face presplit blasting, rotating stoping and comprehensive extraction technologies, which successfully solve the roof management and the gas problems during initial release, achieving good security benefits.

Computational Fluid Dynamics and its Application in Gas Control of Goaf

In recent years, study on the regularity of gas moving has been emphasized due to the more seriously problem of mine gas which caused by the ever increasing of mining depth and rate in the coal. As the important source for the workplace gas, the goaf gas always causes a exceeding of the safety limit at the upper corner, it not only influences the sustainability, stability and security of the mines, but also serves as the primary cause of the accidents. In order to discuss the migration and distributed rule of the goaf gas, this article based on computational fluid dynamics, in accordance with the seepage theory and on the premise of analysised the fluid state of goaf gas, the distribution rule of goaf gas moving has been studied by establishing a mathematical model of gas seepage and distribution in the goaf area with a given boundary condition. The research has provided theoretical basis for the analysis of gas density at the upper corner of the mines, demonstrating its theoretical and practical significance in preventing gas overrun and safeguarding safety in coal mining.

Combined Emission Characteristics and Control Technology of Gob Gas in Ultra-Close Seams

Abstract It is well known that the upper gob gas will gush to working face together with gob gas in mining seam when the lower seam is mined in ultra-close seams. When the layer thickness between two seams is small, the two gobs will become one after the layer collapse, and then the higher concentration gas in upper closed gob will gush out into working face under the negative pressure, which can cause the overrun of gas. The exiting gas problems of lower mining coal in ultra-close seam were analyzed, and then the combined emission characteristic and the reasons of gas overrun were drawn out. In view of this situation, using constant pressurized ventilation (CPV) of windscreen-fan regulator of joint air-pressure, the fans were equipped in haulage roadway and adjustable windscreens were set up in return roadway. In 1001 face, increasing pressure and reducing air volume were implemented by this method; the airflow vectors circuits of before and after using constant pressurized ventilation were analyzed. The practical results showed that the technology of constant pressurized ventilation solved the gas problem successfully, and got the safe effect in this face.