scholarly journals Numerical simulation of boreholes for gas extraction and effective range of gas extraction in soft coal seams

2019 ◽  
Vol 7 (5) ◽  
pp. 1632-1648 ◽  
Author(s):  
Pan Wei ◽  
Changwen Huang ◽  
Xuelong Li ◽  
Shoujian Peng ◽  
Yanan Lu
Keyword(s):  
Numerical Simulation ◽  
Effective Range ◽  
Gas Extraction ◽  
Coal Seams ◽  
Soft Coal

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.

scholarly journals Coupling numerical model of hydraulic fracturing seepage in soft coal based on elastoplastic damage

2020 ◽  
Vol 198 ◽  
pp. 01038
Author(s):  
LI Liangwei
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
Hydraulic Fracturing ◽  
Yield Criterion ◽  
Calculation Model ◽  
Field Application ◽  
Soft Coal ◽  
Plastic Shear Strain ◽  
Strain Relationship ◽  
Relationship Equation

In order to guide the field application of hydraulic fracturing of soft coal in coal mine, based on the elastic-plastic damage theory, the coupling numerical model of soft coal hydraulic fracturing seepage was studied. The porosity strain relationship equation, permeability strain relationship equation, the relationship between permeability and volume plastic tensile strain and volume plastic shear strain of coal and rock mass are derived, and the plastic correction equation and softening parameters are defined. The stress coupling equation and yield criterion are programmed and embedded into the finite difference software FLAC3D for numerical solution. The numerical simulation shows that the numerical calculation model of soft coal hydraulic fracturing conforms to the actual law, and the field fracturing radius investigation experiment is consistent with the numerical simulation results.

Massive Hydraulic Fracturing to Control Gas Outbursts in Soft Coal Seams

2022 ◽  
Author(s):  
Shuaifeng Lyu ◽  
Shengwei Wang ◽  
Junyang Li ◽  
Xiaojun Chen ◽  
Lichao Chen ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Coal Seams ◽  
Soft Coal

scholarly journals Fully Coupled Multi-Scale Model for Gas Extraction from Coal Seam Stimulated by Directional Hydraulic Fracturing

2019 ◽  
Vol 9 (21) ◽  
pp. 4720 ◽  
Author(s):  
Ge ◽  
Zhang ◽  
Sun ◽  
Hu
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Scale Model ◽  
Gas Extraction ◽  
Coal Seams ◽  
Directional Hydraulic Fracturing ◽  
Coal Mine Methane ◽  
Multi Scale ◽  
Fully Coupled

Although numerous studies have tried to explain the mechanism of directional hydraulic fracturing in a coal seam, few of them have been conducted on gas migration stimulated by directional hydraulic fracturing during coal mine methane extraction. In this study, a fully coupled multi-scale model to stimulate gas extraction from a coal seam stimulated by directional hydraulic fracturing was developed and calculated by a finite element approach. The model considers gas flow and heat transfer within the hydraulic fractures, the coal matrix, and cleat system, and it accounts for coal deformation. The model was verified using gas amount data from the NO.8 coal seam at Fengchun mine, Chongqing, Southwest China. Model simulation results show that slots and hydraulic fracture can expand the area of gas pressure drop and decrease the time needed to complete the extraction. The evolution of hydraulic fracture apertures and permeability in coal seams is greatly influenced by the effective stress and coal matrix deformation. A series of sensitivity analyses were performed to investigate the impacts of key factors on gas extraction time of completion. The study shows that hydraulic fracture aperture and the cleat permeability of coal seams play crucial roles in gas extraction from a coal seam stimulated by directional hydraulic fracturing. In addition, the reasonable arrangement of directional boreholes could improve the gas extraction efficiency. A large coal seam dip angle and high temperature help to enhance coal mine methane extraction from the coal seam.

Numerical Simulation of Mixed Emulsion Explosive Charging in Water-Filled-Hole

2013 ◽  
Vol 634-638 ◽  
pp. 3563-3566
Author(s):  
Hai Wang Ye ◽  
Dong Ling Nong ◽  
Ting Li ◽  
Jie Wang Ye
Keyword(s):  
Numerical Simulation ◽  
Water Column ◽  
Water Depth ◽  
Jet Flow ◽  
Hole Diameter ◽  
Water Levels ◽  
Effective Range ◽  
Emulsion Explosive ◽  
Hole Bottom

When charging in water-filled-hole with emulsion mixed loading truck, if the charging hose can not reach the borehole bottom, there will be a water column in the charge. Emulsion explosive charging in water-filled-hole is simulated under three conditions with different water levels, charging velocity and hole diameter when the hose of the explosive mixed loading truck does not reach the hole bottom. The results show that explosive can not reach the bottom of the blasthole if the water depth exceeds the maximum effective range of the jet flow, which is proportional to charging speed and hole diameter, and there will exist a water column at the bottom of the hole. To prevent that, the distance between the hose outlet and the hole bottom must be shorter than the effective range when charging. Besides, increasing charging velocity also works.

scholarly journals Experimental Development of Coal-Like Material with Solid-Gas Coupling for Quantitative Simulation Tests of Coal and Gas Outburst Occurred in Soft Coal Seams

Processes ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 155 ◽  
Author(s):  
Xingkai Wang ◽  
Wenbing Xie ◽  
Zhili Su ◽  
Qingteng Tang
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Influencing Factors ◽  
Co2 Sequestration ◽  
Range Analysis ◽  
Coal Seams ◽  
Gas Outburst ◽  
Soft Coal ◽  
Coal Powder ◽  
Adsorption Desorption

Solid-gas coupling coal-like materials are essential for simulating coal and gas outbursts and the long-term safety study of CO2 sequestration in coal. However, reported materials still differ substantially from natural coal in mechanical, deformation and gaseous properties; the latter two aspects are common not considered. There is a lack of a definite and quantitative preparation method of coal-like materials with high similarity for future reference. Here, 25 groups of raw material ratios were designed in the orthogonal experiment using uniaxial compression, shearing and adsorption/desorption tests. Experiment results indicated that the coal-like materials were highly similar to soft coals in properties mentioned above. And range analysis revealed the key influencing factors of each mechanical index. The gypsum/petrolatum ratio controls the density, compressive strength, elastic modulus, cohesion and deformation characteristic. The coarse/fine coal powder (1–2 and 0–0.5 mm) controls the internal friction angle and is the secondary controlling factor for compressive strength and elastic modulus. The effect of coal particle size on the sample strength was studied using scanning electron microscope (SEM). When the gypsum/petrolatum ratio increased, the deformation characteristics changed from ductile to brittle. The different failure modes in the samples were revealed. The coal powder content is a key in the gas adsorption/desorption properties and an empirical formula for estimating the adsorption capacity was established. Based on the range analysis of experimental results, a multiple linear regression model of the mechanical parameters and their key influencing factors was obtained. Finally, a composition closely resembling the natural coal was determined, which differs by only 0.47–7.41% in all parameters except porosity (11.76%). Possible improvements and extension to similar materials are discussed. The findings of this study can help for better understanding of coal and gas outburst mechanism and stability of CO2 sequestration in soft coal seams.

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