Damage and deformation control equation for gas-bearing coal and its numerical calculation method

Hu, Shaobin; Wang, Enyuan; Kong, Xiangguo

doi:10.1016/j.jngse.2015.04.039

Cited by 33 publications

(12 citation statements)

References 37 publications

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“…Based on the same damage constitutive equation, Yang et al and Zheng et al directly used the damage variable to modify the elastic permeability models to obtain the damage‐induced permeability models, respectively. Espinoza et al and Hu et al established the damage dual‐pore constitutive equations of coal, respectively. Take into account these equations, they established damage‐induced dual‐pore permeability model, respectively.…”

Section: Introductionmentioning

confidence: 99%

Damage‐induced permeability model of coal and its application to gas predrainage in combination of soft coal and hard coal

Zhang

et al. 2019

Energy Science & Engineering

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Coal permeability is a key parameter that affects the drainage of coal bed methane (CBM). Owing to the lower original permeability of coal seams in China, more attention was paid to the study of damage‐induced permeability laws. However, the theory of damage‐induced permeability still needs to be improved. In this paper, the permeability evolution experiments during the complete stress–strain process of coal were carried out firstly. The results are shown that with the increase in axial strain, the coal permeability decreases slowly at first, then increases rapidly, and finally increases slowly or even remains unchanged, and the peak stress point can be regarded as the extreme point of permeability. Then, the equivalent plastic strain was used to describe the damage of coal. Based on the above results, a new damage‐induced permeability model was developed, and the new model can match the experimental data of permeability very well. In addition, solid–gas coupling models of coal were developed based on the new permeability model, and the numerical results show that there is a region of sudden increase in permeability around the borehole where plastic failure occurs, which indicates that the damage‐induced permeability model is reasonable. Finally, the results of numerical simulation of gas predrainage in combination of soft coal and hard coal under different cases were used to optimize the borehole layout of gas predrainage in the field.

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Section: Introductionmentioning

confidence: 99%

Damage‐induced permeability model of coal and its application to gas predrainage in combination of soft coal and hard coal

Zhang

et al. 2019

Energy Science & Engineering

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“…The boundary conditions of the fracturing model were established based on the explosion pressure data obtained from FLACS simulation and relevant coal parameters measured in the laboratory (Table 2). Additionally, we developed the pore elasticity and Biot seep model, and evaluated the fracturing effect under explosion pressure using COMSOL simulation 23,24 . Finally, the explosive fracturing effect was quantified using parameters, such as coal seam stress, gas pressure, and coal permeability changes.…”

Section: Methodsmentioning

confidence: 99%

Numerical investigation of the in situ gas explosion fracturing and the enhancement of the penetration in coal seam boreholes

Qiao,

Zhang,

Yuan

et al. 2023

Energy Science & Engineering

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Permeability enhancement of low permeability coal seams is a key tool in coal mine gas extraction and utilization. Numerical investigations are used to analyze the geometric parameters of the drilled gas cavity and the effect of initial pressure on explosion parameters to explore the potential of original gas blasting in enhancing crack penetration in coal seams. On the basis of these analyses, the changes in characteristic parameters of the coal body under blasting pressure are examined. The results show that the maximum explosion pressure tends to be close to the theoretical explosion maximum when the L/Φ is 1.67–2.5, and the mechanical effect of the explosion pressure and surge velocity on the wall reaches the optimum in the experimental group when the L/Φ is 1.67. The initial pressure and the maximum explosion pressure demonstrate a linear positive correlation, and increasing the former can effectively enhance the force applied to the hole wall. During the gas explosion pressurization stage, the cracking range of coal under pressure is 0.05 m, but the duration of peak pressure can extend the range of cracking. The combined effect of the stress and pressure fields causes elastic energy storage in the coal body to fail in the radial region of the hole wall, but regains elastic energy storage as the pressure increases. The effect of fracturing on the radial coal seam permeability of the borehole wall before and after the fracturing effect is expanded by 19.6 times, proving that in situ gas explosion in boreholes can effectively improve the gas seepage characteristics of coal seams and increase the gas recovery rate. The simulations indicate that the application of in situ gas explosion fracturing and permeation technology is limited by the increase in maximum explosion pressure and the cumulative effect time of the peak pressure. This provides a theoretical basis for understanding the constraints of gas explosion fracturing and permeation technology.

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“…During the quasi-static loading stage, air pressure p g is applied around the hole and in-situ stress boundary σ bx and σ by are applied to the external boundary. Its physico-mechanical parameters is specified according to a typical coal experimented by other researchers Pan et al, 2013;Hu et al, 2015), as listed in Table 2.…”

Section: The Effect Of High-pressure Air Blasting On Gas Drainage Fromentioning

confidence: 99%

High-pressure air blasting experiments on concrete and implications for enhanced coal gas drainage

Zhu

Gai

Wei

et al. 2016

Journal of Natural Gas Science and Engineering

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High-pressure air blasting is one type of distressing blasting techniques to enhance gas drainage in coal seams and thus to prevent coal and gas outbursts. In this work, firstly, high-pressure air blasting experiment is conducted on concrete specimen with a size of 600 mm × 600 mm × 600 mm, the blasting crack distribution is observed and the particle vibration acceleration at the outer boundary of the sample is monitored. Then a damage model for high-pressure air blasting is proposed when the loading induced by high-pressure air blasting is considered as two consecutive stages, i.e. the dynamic loading stage induced by the stress wave and the quasi-static loading stage induced by quasi-static air pressure. Based on the experimental curve of particle vibration acceleration and corresponding numerical simulation, the stress wave distribution with Gaussian form around the borehole is inversed. In addition, the blasting induced damage evolution in the concrete specimen is numerically simulated, and the numerical result of final cracking pattern compares favorably with the experimental observation. During the high-pressure air blasting on concrete block, the blasting stress wave initiates primarily radial cracks and the crushed zone, and the quasi-static air pressure results in the extension of existing cracks and the expansion of crushed zone. Compared to the hydraulic fracturing with water, the high-pressure air blasting induces more fractures, which would be of great benefit to the enhanced gas drainage in coal seam. Finally, by considering the effect of coal seam damage on permeability, the gas drainage that may be enhanced by high-pressure air blasting is quantified based on the numerical simulations. It is demonstrated the damage induced by high-pressure air blasting around the borehole enhances the gas drainage dramatically; however the in-situ stress in coal seam may retrain the blasting-induced fractures and subsequent gas drainage, which should be paid attention to during the design of enhanced gas drainage with high-pressure air blasting.

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Damage and deformation control equation for gas-bearing coal and its numerical calculation method

Cited by 33 publications

References 37 publications

Damage‐induced permeability model of coal and its application to gas predrainage in combination of soft coal and hard coal

Damage‐induced permeability model of coal and its application to gas predrainage in combination of soft coal and hard coal

Numerical investigation of the in situ gas explosion fracturing and the enhancement of the penetration in coal seam boreholes

High-pressure air blasting experiments on concrete and implications for enhanced coal gas drainage

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