scholarly journals REASONS OF MINE ACCIDENT OCCURING WITH DISASTROUS CONSEQUENCES

2019 ◽  
Vol 2 (5) ◽  
pp. 20-26
Author(s):  
Vladimir Skritsky
Keyword(s):  
Coal Dust ◽  
Coal Seams ◽  
Explosion Wave ◽  
Working Face ◽  
High Efficient ◽  
Mine Accident ◽  
Technical Solutions

In the work it is proved that methane explosions with disastrous consequences have become after conversion to high-effective mining of extraction pillar during mining flat and steep coal seams at functioning extracting areas. It is established that during high-efficient mining of extracting areas, first combustion and methane explosions happen at worked space, where they are initiated with occurred and non-noticed places of coal self-ignition. From worked space burning methane outbursts by explosion wave from the cove to the working face and near workings where the explosion develops with coal dust presence. Technical solutions for prevention such accidents are proposed.

scholarly journals Comprehensive technical support for safe mining in ultra-close coal seams: A case study

2021 ◽  
pp. 014459872110093
Author(s):  
Wei Zhang ◽  
Jiawei Guo ◽  
Kaidi Xie ◽  
Jinming Wang ◽  
Liang Chen ◽  
...  
Keyword(s):  
Coal Seam ◽  
Technical Support ◽  
Surrounding Rock ◽  
Coal Seams ◽  
Deformation Control ◽  
Hard Roof ◽  
Working Face ◽  
Close Coal Seams ◽  
Safe Mining

In order to mine the coal seam under super-thick hard roof, improve the utilization rate of resources and prolong the remaining service life of the mine, a case study of the Gaozhuang Coal Mine in the Zaozhuang Mining Area has been performed in this paper. Based on the specific mining geological conditions of ultra-close coal seams (#3up and #3low coal seams), their joint systematic analysis has been performed, with the focus made in the following three aspects: (i) prevention of rock burst under super-thick hard roof, (ii) deformation control of surrounding rock of roadways in the lower coal seam, and (iii) fire prevention in the goaf of working face. Given the strong bursting tendency observed in upper coal seam and lower coal seam, the technology of preventing rock burst under super-thick hard roof was proposed, which involved setting of narrow section coal pillars to protect roadways and interleaving layout of working faces. The specific supporting scheme of surrounding rock of roadways in the #3low1101 working face was determined, and the grouting reinforcement method of local fractured zones through Marithan was further proposed, to ensure the deformation control of surrounding rock of roadways in lower coal seams. The proposed fire prevention technology envisaged goaf grouting and spraying to plug leaks, which reduced the hazard of spontaneous combustion of residual coals in mined ultra-close coal seams. The technical and economic improvements with a direct economic benefit of 5.55 million yuan were achieved by the application of the proposed comprehensive technical support. The research results obtained provide a theoretical guidance and technical support of safe mining strategies of close coal seams in other mining areas.

scholarly journals Optical Estimation on Pollution Level of Respirable Dust Based on Infrared Transmitting Behavior in Coalmine Fully Mechanized Working Face

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Wen-Zheng Wang ◽  
Yan-Ming Wang ◽  
Guo-Qing Shi
Keyword(s):  
Coal Particle ◽  
Coal Dust ◽  
Operating Conditions ◽  
Dust Concentration ◽  
Optical Channel ◽  
Pollution Level ◽  
Engineering Practice ◽  
Dust Generation ◽  
Working Face ◽  
Comparison Results

Respirable coal particle generated during underground mining is the main cause for gas-dust explosions and coal workers’ pneumoconiosis (CWP) which needs accurate monitoring especially on its concentration. Focusing on the coal dust pollution in the fully mechanized working face of Huangbaici coalmine, coal particle was sampled for further industrial analysis and FT-IR test to obtain its chemical composition and optical constant. Combined with the simulated spatial distribution of airborne dust, the spectral transmission characteristics of coal dust within wavelengths of 2.5 to 25 μm under different operating conditions were obtained. The simulation results show that the transmittance and aerosol optical depth (AOD) of coal dust are closely linked and obviously influenced by the variation of dust generation source (intensity of dust release, position of coal cutting, and the wetting of the coal seam) and airflow field (wind speed and direction of ventilation). Furthermore, an optical channel of 1260–1280 cm−1(7.937–7.813 μm) which is almost only sensitive to the variation of dust concentration but dull to the diameter change of coal dust was selected to establish the correlation of dust concentration and infrared transmittance. The fitting curve was then applied to retrieve the equivalent dust concentration based on optical information, and the comparison results demonstrate that the estimated pollution level is consistent with field measurement data in engineering practice.

scholarly journals Surrounding Rock Movement of Steeply Dipping Coal Seam Using Backfill Mining

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Wenyu Lv ◽  
Kai Guo ◽  
Jianhao Yu ◽  
Xufeng Du ◽  
Kun Feng
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Surrounding Rock ◽  
Maximum Deflection ◽  
Coal Seams ◽  
Physical Similarity ◽  
Working Face ◽  
Rock Structure ◽  
Backfill Mining ◽  
The Stability

The movement of the overlying strata in steeply dipping coal seams is complex, and the deformation of roof rock beam is obvious. In general, the backfill mining method can improve the stability of the surrounding rock effectively. In this study, the 645 working face of the tested mine is used as a prototype to establish the mechanical model of the inclined roof beam using the sloping flexible shield support backfilling method in a steeply dipping coal seam, and the deflection equation is derived to obtain the roof damage structure and the maximum deflection position of the roof beam. Finally, numerical simulation and physical similarity simulation experiments are carried out to study the stability of the surrounding rock structure under backfilling mining in steeply dipping coal seams. The results show the following: (1) With the support of the gangue filling body, the inclined roof beam has smaller roof subsidence, and the maximum deflection position moves to the upper part of working face. (2) With the increase of the stope height, the stress and displacement field of the surrounding rock using the backfilling method show an asymmetrical distribution, the movement, deformation, and failure increase slowly, and the increase of the strain is relatively stable. Compared with the caving method, the range and degree of the surrounding rock disturbed by the mining stress are lower. The results of numerical simulation and physical similarity simulation experiment are generally consistent with the theoretically derived results. Overall, this study can provide theoretical basis for the safe and efficient production of steeply dipping coal seams.

Design of High-Efficient Bits for Igneous Rock in Xushen Gasfield

2013 ◽  
Vol 385-386 ◽  
pp. 308-311
Author(s):  
Li Gang Zhang ◽  
Tie Yan ◽  
Shi Bin Li
Keyword(s):  
Tungsten Carbide ◽  
Design Method ◽  
Polycrystalline Diamond ◽  
High Hardness ◽  
Rake Angle ◽  
Gas Field ◽  
Working Face ◽  
High Efficient ◽  
Low Efficiency ◽  
Bit Life

The igneous rocks in deep formations of the Xushen gasfield have the following characters: high abrasive property, high hardness, and high drillability, which lead to many drill bit accidents, few footage per bit , low efficiency of drilling, long drilling cycle, these severely restrict the exploration and development process of gas field. According to the features of deep formation, a hybird cutters bit is designed. It has three cones, with the overhang cone , duplicate taper and offset cone characters. The tungsten carbide cutters and the polycrystalline diamond compacts cutters are alternative collocation in the same tooth row in the bit. The exposed height of the tungsten carbide cutters is higher than polycrystalline diamond compacts cutters. The back rake angle of polycrystalline diamond compacts cutters is 10 ~ 40 °, the side rake angle is 10 ~ 30 °. The normal direction of working face stay the same with the composite slip direction, and the side rake pointed at adjacent gullet. Through the design method, it is integrated that the advantages of roller bit and PDC bit, the way of impact breakage and rotational shear breakage and the prominent performance of tungsten carbide cutters and polycrystalline diamond compacts cutters. It can improveROP and bit life.

scholarly journals Optimizing Simulation and Analysis of Automated Top-Coal Drawing Technique in Extra-Thick Coal Seams

Energies ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 232 ◽  
Author(s):  
Qunlei Zhang ◽  
Ruifu Yuan ◽  
Shen Wang ◽  
Dongyin Li ◽  
Huamin Li ◽  
...  
Keyword(s):  
Numerical Models ◽  
Time Estimation ◽  
Engineering Practice ◽  
Coal Seams ◽  
Control Approach ◽  
Working Face ◽  
Geological Conditions ◽  
Round Number ◽  
Element Approach ◽  
Drawing Technique

A particle element approach based on continuum-discontinuum element method (CDEM) is applied to optimize the automated top-coal drawing techniques in extra-thick coal seams. Numerical models with 100 drawing openings are created according to the field engineering geological conditions of Tongxin coal mine in China. An automated coal drawing control approach in numerical modelling based on time criterion is proposed. The rock mixed rate, top-coal recovery rate and the variance of the drawn top coal amount are counted and set as the statistical indicators to evaluate the top-coal drawing techniques. The traditional top-coal drawing criterion, “rocks appear, close the opening”, leads to low recovery of top coal and waste of coal resources in extra-thick coal seams, significantly weakening the transport stability and efficiency of the scraper conveyer. A three-round unequal time top-coal drawing technique is proposed for automated top-coal drawing. Three drawing openings, corresponding to the three top-coal drawing rounds respectively, are working at the same time; in each round, the top-coal drawing sequence is from the first drawing opening at one end of the working face to last drawing opening at another end; the drawing time of each round is not equal and increases with the round number. The numerical inversion approach of iteration steps can be used for real top-coal drawing time estimation and automated drawing process design to achieve a better top coal drawing effect, while the exact time for each drawing round still needs to be corrected by engineering practice.

Numerical Simulation of Underground Pressure in Mining High-Inclined Coal-Seam with Analysis of Material Properties in Mine Dongbaowei

2013 ◽  
Vol 644 ◽  
pp. 382-386 ◽  
Author(s):  
Ming Ming Wen
Keyword(s):  
Coal Seam ◽  
In Situ Observation ◽  
Coal Seams ◽  
Relevant Model ◽  
Roof Caving ◽  
Deformation Feature ◽  
Working Face ◽  
Strata Behavior ◽  
Surrounding Rock Stress

The FLAC software is used in establishing a relevant model to study the strata behavior of fully mechanized working face of steep coal seams. Using this model, we have simulated the roof caving characteristic and the stress distribution of surrounding rocks and analyzed the deformation feature of the surrounding rocks in the working face end. Based on the in-situ observation about the fully mechanized working face, we have obtained the surrounding rock stress and the strata behavior of steep coal seam and proposed some countermeasures aiming at these problems.

Study on Regularity of Coal Mine Blasting Accidents of China after 2000

2013 ◽  
Vol 368-370 ◽  
pp. 2014-2020
Author(s):  
Ji Ye Dong ◽  
Gui Fu ◽  
Ze Chen ◽  
Shuai Dong Jia
Keyword(s):  
Coal Mine ◽  
Main Type ◽  
Coal Dust ◽  
Dust Explosion ◽  
The Past ◽  
Coal Mine Gas ◽  
Working Face ◽  
Parabolic Trajectory ◽  
The Common ◽  
Coal Enterprises

In this article, 133 massive colliery blasting accidents were statistically analyzed in China after 2000, mainly from two aspects of the accident number and death number, three aspects such as the type of accidents, the time rule of accidents, and provincial were analyzed statistically; 72 massive colliery blasting accidents caused by blasters were analyzed statistically with regard to the unsafe act of blasters. The statistical results show that the accident and death number presents a downward opening parabolic trajectory by year; The time of the accident is more concentrated, and the fate casualties happened frequently around March, July, November and December, February is the least; Coal mine gas accident is the main type of blasting accidents, and the coal dust explosion accident causes most deaths averagely; The past statistical method seriously neglected the seriousness of blasting accidents; The coal mine underwent massive colliery blasting accidents distribute widely, but six provinces (Guizhou, Shanxi, Heilongjiang, Sichuan, Henan, Hunan, Liaoning) are the key places of blasting accidents; There are 22 species of unsafe act to blasters, the most common unsafe act is no working face environmental inspection, material and tools be used unsafely and improperly. Coal enterprises, government, and regulators should strengthen the prevention of the key time, accident style, region, and the common unsafe blasting act to the regularity of coal mine blasting accidents.

scholarly journals Study on Surrounding Rock Structure Evolution Characteristics and Roof Control Techniques of the Retained Roadway Formed by Roof Cutting in Inclined Coal Seams

2021 ◽  
Vol 2021 ◽  
pp. 1-20
Author(s):  
Guangyuan Yu ◽  
Jiong Wang ◽  
Jianjun Ren ◽  
Jinzhu Hu ◽  
Zhifu Pan ◽  
...  
Keyword(s):  
Structure Evolution ◽  
Coal Seams ◽  
Supporting System ◽  
Working Face ◽  
Evolution Characteristics ◽  
Rock Structure ◽  
Support Resistance ◽  
Pillar Mining ◽  
Three Stages ◽  
Constant Support

To control the roof during gob-side entry retaining by roof cutting in inclined coal seams, the retained gob-side roadway is zoned based on the mechanical principle and technological process of no-pillar mining with gob-entry retention. A simplified mechanical model for surrounding rocks in different subzones was established by using theoretical analysis and numerical simulation to attain the demand for the support resistance and deformation of the roof in different subzones. According to load and deformation characteristics of the roof and mechanical characteristics of NPR cables, single props, and a sliding-type gangue-retaining structure formed by U-shaped steel inserts, the supporting systems for roadways in different subzones and the constitutive model thereof were established. On this basis, the action of the supporting system was analysed and a field test was performed. The results show that the supporting system undergoes three stages of behaviour, i.e., pressure growth, yielding under constant pressure, and stabilisation during whole entry retention. It can guarantee the collaborative deformation of the supporting systems with the roof on the premise of constant support resistance, thus satisfying the requirement for roadway protection. The roadway 150 m back from the working face is stable, and the final convergence between the roof and floor of the retained entry is 257 mm, showing a favourable entry-retention effect.

scholarly journals An Approach to Dynamic Disaster Prevention in Strong Rock Burst Coal Seam under Multi-Aquifers: A Case Study of Tingnan Coal Mine

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7287
Author(s):  
Xinxin Zhou ◽  
Zhenhua Ouyang ◽  
Ranran Zhou ◽  
Zhenxing Ji ◽  
Haiyang Yi ◽  
...  
Keyword(s):  
Rock Burst ◽  
Coal Mine ◽  
Water Inrush ◽  
Coal Seams ◽  
High Position ◽  
Integrated Method ◽  
Working Face ◽  
Strong Rock ◽  
And Control

In order to prevent the multi-dynamic disasters induced by rock burst and roof water inrush in strong rock burst coal seams under multi-aquifers, such as is the case with the 207 working face in the Tingnan coal mine considered in this study, the exhibited characteristics of two types of dynamic disasters, namely rock burst and water inrush, were analyzed. Based on the lithology and predicted caving height of the roof, the contradiction between rock burst and water inrush was analyzed. In light of these analyses, an integrated method, roof pre-splitting at a high position and shattering at a low position, was proposed. According to the results of numerical modelling, pre-crack blasting at higher rock layers enables a cantilever roof cave in time, thereby reducing the risk of rock burst, and pre-crack blasting at underlying rock layers helps increase the crushing degree of the rock, which is beneficial for decreasing the caving height of rock layers above goaf, thereby preventing the occurrence of water inrush. Finally, the proposed method was applied in an engineering case, and the effectiveness of this method for prevention and control of multi-dynamics disasters was evaluated by field observations of the caving height of rock layers and micro-seismic monitoring. As a result, the proposed method works well integrally to prevent and control rock burst and water inrush.

scholarly journals The Influence of Fracture Strain Energy on the Burst Tendency of Coal Seams and Field Application

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Hongjun Guo ◽  
Ming Ji ◽  
Dapeng Liu ◽  
Mengxi Liu ◽  
Weisheng Zhao
Keyword(s):  
Strain Energy ◽  
Fracture Strain ◽  
Base Material ◽  
Field Application ◽  
Coal Seams ◽  
Cyclic Loading And Unloading ◽  
Working Face ◽  
Coal Deformation ◽  
Fracture Development ◽  
Plastic Strain Energy

Coal is typically considered a special engineering rock mass because of its low strength, high internal fracture development, good permeability, and random distribution of microparticles and fractures. The results of cyclic loading and unloading tests indicate that the strain energy during the coal deformation process can be divided into three parts: plastic strain energy; fracture strain energy; and base-material strain energy. The energy composition ratio differs depending on coal strength. Lower proportions of fracture strain energy are associated with higher elastic energy indexes, and there is a negative correlation between fracture strain energy and other coal burst tendency indexes. The results were applied on the 4206 isolated island working face of coal mine A in Yan’an, Shanxi, China, yielding good benefits. The findings presented here provide a theoretical basis for understanding the principle of coal seam bursting and guidance for reducing burst risks.

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