scholarly journals Study of the influencing factors of the liquid CO2 phase change fracturing effect in coal seams

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0254996
Author(s):  
Jinzhang Jia ◽  
Dongming Wang ◽  
Bin Li ◽  
Xiuyuan Tian
Keyword(s):  
Coal Seam ◽  
Phase Change ◽  
Peak Pressure ◽  
In Situ Stress ◽  
Simulation Software ◽  
Hole Diameter ◽  
Gas Pressure ◽  
Physical Parameters ◽  
Simulation Results

To study the influence of different factors on the cracking effect of the liquid CO2 phase transition, the mechanics of coal rock crack extension based on liquid CO2 phase change blast loading were studied. Through the application of simulation software to analyze the influence of coal seam physical parameters (in situ stress, gas pressure, modulus of elasticity and strength of coal) and blasting parameters (fracturing pore size and peak pressure of detonation)on the effect of liquid CO2 phase change cracking, the simulation results showed that the cracking effect of liquid CO2 phase change was positively correlated with the changes in gas pressure, elastic modulus, fracture hole diameter and peak vent pressure, negatively correlated with the variation in situ stress and compressive strength, and nearly independent of the tensile strength. In addition, by using Gray correlation analysis to analyze the influence degree of six main factors on the cracking effect, the calculation results showed that the effect of blasting parameters was greater than that of physical parameters. The main controlling factor that affected the blasting effect was the peak pressure of blasting release. By conducting comparative engineering trials with different blasting parameters, the test results showed that the crack effect of the coal seam was positively correlated with the change in fracture hole diameter and peak venting pressure, which was consistent with the results obtained from the simulation. The experimental results and simulation results for the effective radius of coal seam fracturing were basically consistent, with the error between the two types of results falling below 10%. Therefore, the reliability of the blasting numerical model was verified. In summary, the research results provide theoretical guidance for applying and promoting liquid CO2 fracturing technology in coal mines.

scholarly journals Characteristics of in situ stress and its influence on coal seam permeability in the Liupanshui Coalfield, Western Guizhou

2021 ◽  
Author(s):  
Xiaojie Fang ◽  
Caifang Wu ◽  
Xiuming Jiang ◽  
Ningning Liu ◽  
Dan Zhou ◽  
...  
Keyword(s):  
Coal Seam ◽  
In Situ Stress ◽  
Western Guizhou

scholarly journals Study on Occurrence Mechanism of Coal Pillar in L-Shaped Zone during Fully Mechanized Mining Period and Prevention Technology

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Zeng-qiang Yang ◽  
Hong-mei Wang ◽  
De-quan Sun ◽  
Xian-jian Ma ◽  
Ming-bao Xu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Rock Burst ◽  
Dynamic Load ◽  
Static Load ◽  
Coal Pillar ◽  
Simulation Software ◽  
In Situ Investigation ◽  
Simulation Results ◽  
Occurrence Mechanism

In order to study the occurrence mechanism of rock burst in L-shaped zone during a fully mechanized mining period, the No. 705 working face which is located in Baojishan Colliery is taken as a typical engineering background. By means of in situ investigation, theoretical analysis, numerical simulation, in situ tests, and relevant monitoring methods, the occurrence mechanism of rock burst and corresponding prevention technology are studied. The results show that a coal pillar with some confining pressure in the L-shaped zone is established by FLAC3D numerical simulation software, and the numerical simulation results indicate that the change in static load has a greater effect than dynamic load on coal pillar unstable failure; the static load plays a role in storing energy, and dynamic load plays a role in inducing rock burst; the bolt-mesh-cable support and high-pressure water jet unloading combined technology is put forward to prevent rock burst in roadways, and the numerical simulation results show that stress distribution of surrounding rock meets the model of strong-soft-strong (3S) structure, and the moment distribution is reasonable. In the follow-up mining, a limit value of coal fines is used to determine that this measure is a reasonable method to prevent rock burst. The study conclusions provide theoretical foundation and new guidance for preventing rock burst by synergistic effect technology in roadways.

scholarly journals Research on the Disaster-Inducing Mechanism of Coal-Gas Outburst

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
Fengxiang Nie ◽  
Honglei Wang ◽  
Liming Qiu
Keyword(s):  
Coal Mining ◽  
In Situ Stress ◽  
Gas Pressure ◽  
Underground Coal Mining ◽  
Coal Gas ◽  
Gas Outburst ◽  
Mining Depth ◽  
Mining Coal ◽  
Occurrence Mechanism

In China, coal-gas outburst is seriously affecting safety of the coal mine. To improve the safety status of underground coal mining, this work investigated the evolution process and occurrence mechanism of coal-gas outburst under the coupling action of stress and gas. Results show that increasing either gas pressure or in-situ stress can make coal destroy and destabilize, and the contribution of gas pressure to coal failure is twice that of in-situ stress. In ultradeep coal mining, coal-gas outburst may occur even under the condition of low gas pressure due to large in-situ stress. Moreover, the larger the mining depth is, the lower the gas index is required for disaster occurrence. The results have certain guiding significance for coal energy mining and the control of coal-gas outburst in deep coal mining.

scholarly journals Damage Characteristics and Mechanism of a 2010 Disastrous Groundwater Inrush Occurred at the Luotuoshan Coalmine in Wuhai, Inner Mongolia, China

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 655 ◽  
Author(s):  
Fangpeng Cui ◽  
Qiang Wu ◽  
Chen Xiong ◽  
Xiang Chen ◽  
Fanlan Meng ◽  
...  
Keyword(s):  
Coal Seam ◽  
Inner Mongolia ◽  
In Situ Stress ◽  
Economic Losses ◽  
Karst Collapse ◽  
Great Effort ◽  
Groundwater Inrush ◽  
Collapse Column ◽  
Great Damage

On 1 March 2010, a disastrous groundwater inrush occurred at the Luotuoshan coalmine in Wuhai (Inner Mongolia, China). Great effort was taken during the post-accident rescue. However, triggered by a large amount of groundwater rushed in from the Ordovician limestone aquifer underlying the No.16 coal seam through the fractured sandy claystone and the karst collapse column, it caused great damage, including 32 deaths and direct economic losses of over 48 million yuan. The groundwater inrush originated from the floor heave in the air return gallery of the No.16 coal seam. The peak inflow rate was 60,036 m3/h. The gallery excavation under conditions caused by the incompletely recognized hydrogeological environment induced the accident. The unidentified spatial distribution of the karst collapse column triggered the accident directly. The high-pressure groundwater accumulated in the collapse column and the gallery excavation, which caused the redistribution of the in situ stress, contributing to progressive fractures in the floor of the No. 16 coal seam. Eventually, an intensive water-conductive passage consisting of the fractured floor and the karst collapse column formed. Administratively/technically, that mandatory regulations on gallery excavation were not carried out which contributed the accident. Moreover, the poor awareness about groundwater inrush recognition and quick remediation also contoirbuted to the disastrous extent of the accident.

scholarly journals Slotting effect on pressure relief during gas drainage of low permeability coal

2019 ◽  
Vol 23 (3 Part A) ◽  
pp. 1547-1553
Author(s):  
Yanan Gao ◽  
Guanghui Dong ◽  
Hao Wang ◽  
Xueyun Chang
Keyword(s):  
In Situ Stress ◽  
Gas Pressure ◽  
Discontinuous Deformation Analysis ◽  
Deformation Analysis ◽  
Gas Drainage ◽  
Mining Depth ◽  
Ground Pressure ◽  
Discontinuous Deformation ◽  
Rheology Property

As the increase of the mining depth in China, the underground temperature, in situ stress and CH4 gas pressure also increase. Such factors have great influences on the gas drainage engineering. In this paper, the discontinuous deformation analysis is used to model the stress relief effect of drilling and slot. The effects of slot width, height, and ground pressure was analyzed. The rheology property of the coal mass under different temperature and gas pressure are also studied. the results of this paper can be used as a reference for gas drainage engineering in coal mine.

scholarly journals Study on Temporal and Spatial Characteristics of Overlying Strata in Deep Coal Mining Process

2021 ◽  
Author(s):  
Bang-an Zhang ◽  
Yang yushun ◽  
Dong-ming Zhang
Keyword(s):  
Stress Concentration ◽  
Coal Seam ◽  
Coal Mining ◽  
Three Dimensional ◽  
In Situ Stress ◽  
Three Dimensional Model ◽  
Concentration Coefficient ◽  
Working Face ◽  
Stress Concentration Coefficient

Abstract This paper adopts the stress relief method to test the in-situ stress in the field to obtain the in-situ stress distribution characteristics of No. 2+3# coal seam. A three-dimensional model was established with the No. S3012 working face as the engineering background, and the measured in-situ stress values ​​were applied to the three-dimensional model, and the spatial-temporal evolution characteristics of coal and rock mass around the stope during coal seam mining were studied. The specific conclusions are as follows: the three-dimensional stress distribution map in front of, behind and on both sides of the working face in the process of coal mining are obtained. As the working face goes on, the maximum value of the supporting stress formed in front of, behind and on both sides of the working face shifts to the corner, presenting a “hump-like” distribution. The stress concentration coefficient of front, back and both sides of stope increases linearly with the increase of mining size. Under the same mining size, the stress concentration coefficient in front of stope is the smallest, and the stress concentration coefficient on both sides is the largest. The three-dimensional displacement field distribution nephogram of overlying strata in the process of coal mining is obtained. With the continuous advance of the working face, the roof strata of coal seam undergo continuous dynamic subsidence process, and the roof subsidence increases continuously, showing the shape of "bowl" with sharp bottom. In the process of working face mining, the roof displacement of coal seam showed an "O" shape evolution characteristic. The three-dimensional distribution cloud map of the plastic zone of coal and rock mass in the process of working face mining was obtained, and the failure volume of the plastic zone gradually increases with the continuous progress of the working face.

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