Numerical Modeling on Hydraulic Fracturing in Coal-Rock Mass for Enhancing Gas Drainage

Yuan, Zhigang; Shao, Yaohua

doi:10.1155/2018/1485672

Cited by 10 publications

(7 citation statements)

References 27 publications

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“…e similar material simulation experiment is a reduced-scale approach according to similarity criteria [24][25][26]. e selected similar Advances in Civil Engineering materials must have very similar physicomechanical properties of engineering prototype (referred as coal-rock strata here).…”

Section: Similarity Criteria and Similar Materialmentioning

confidence: 99%

“…e type and proportion parameters of similar material determine whether experimental results obtained can represent mechanical responses of prototype. Similar material simulation experiments have been widely employed, but how to obtain accurate and optimum proportioning parameters is urgently needed to be investigated in coal mining [20][21][22][23][24][25][26]. In this section, the river sand, cement (containing gypsum and y ash), and water are used and mixed to manufacture a new similar material, which is used to represent various coal-rock strata around the protective layer in the coal mine.…”

Section: Similarity Criteria and Similar Materialmentioning

confidence: 99%

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Similar Material Simulation Study on Protection Effect of Steeply Inclined Upper Protective Layer Mining with Varying Interlayer Distances

Yuan

Shao

Zhu

2019

Advances in Civil Engineering

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Protective layer mining, as a dominating regional prevention measure, is generally adopted to prevent and control gas disasters in highly gassy or outburst mines of China. Interlayer distance is one of the most important factors that influences protection effect. However, how does interlayer distance affect the protection effect of steeply inclined upper protective layer mining is not understood fully. According to the engineering practice in Nantong mining district, a new method for similar material simulation experiment of steeply inclined upper protective layer mining is proposed, in which an orthogonal test of similar materials comprising of sand, cement (containing gypsum and fly ash), and water mixture is conducted to obtain relations between proportioning parameters and mechanical properties using a multiple regression method. And then the method is applied to study the protection effect of steeply inclined upper protective layer mining with varying interlayer distances. e results show the following. (1) e proportioning parameters of similar material have strong linear relations with its mechanical properties, and mechanical behaviors of such similar material denote that it can simulate most coal-rock lithologies in coal mine. (2) Both pressure-relief curves and swelling strain curves for protected layer present convex shapes; protection angles at lower excavation boundary are greater than those of upper excavation boundary; with the increase of interlayer distance, the pressure-relief curve evolves from pattern "∩" to pattern "∧" and corresponding pressure-relief region becomes narrower, the center of pressure-relief region tends to transfer to the corresponding center of upper protective layer excavation region, the stress concentration coefficient decreases, the protection angles change little, and the length of the protection region reduces dramatically. (3) e protection region and protection angle calculated based on swelling strain of 3‰ are less than the empirical values based on the dip angle in Provisions, denoting that the method proposed in this study is safer than that in Provisions. e research results provide a useful guide for layouts of roadway and gas drainage boreholes to prevent gas disaster in Nantong coal mine district.

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Section: Similarity Criteria and Similar Materialmentioning

confidence: 99%

Section: Similarity Criteria and Similar Materialmentioning

confidence: 99%

Similar Material Simulation Study on Protection Effect of Steeply Inclined Upper Protective Layer Mining with Varying Interlayer Distances

Yuan

Shao

Zhu

2019

Advances in Civil Engineering

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“…Lin et al [19] constructed a gas flow model for gas flowing in coal body around the boreholes, they wrote and complied a simulation program for calculating the gas flow surrounding the boreholes and used it to solve the relationship between effective drainage radius and drainage time, and they proposed a computer simulation method for determining the effective drainage radius of boreholes. Yuan and Shao [20] studied the method of hydraulic fracturing to improve the high permeability of coal and rock by using the method of numerical simulation. The research results show that the gas drainage effect can be improved by using hydraulic fracturing for coal and rock with certain hardness.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Borehole Parameters for Coal Seam Gas Pre-Drainage

Li¹,

Zheng²,

Liu³

2021

IJHT

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Borehole parameters are quite important for gas drainage. This paper studies the impact of borehole diameter and time on gas drainage and performs numerical simulation on the distribution of gas pressure under the conditions of different borehole diameters and drainage times. The simulation results reveal that, as the borehole diameter increases, the gas drainage volume increases along with it and the gas pressure decreases, but such effect on gas drainage is limited. In terms of drainage time, the longer the drainage time, the greater the drainage impact scope. Taking a gas pressure drop of 51% as the indicator of the effective pre-drainage radius, the distance from the point with a gas pressure drop of 51% to the position of the borehole is the effective pre-drainage radius. When the pre-drainage reached the 30th, 45th, 60th, 75th, and 90th day, the effective pre-drainage radius was 1.04m, 1.29m, 1.51m, 1.68m, and 1.82m respectively. According to the numerical simulation results, the effective pre-drainage radius varies with the pre-drainage time, and the fitting analysis of the two indicates that the relationship between the two can be described by a power function.

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“…The extraction of coalbed methane before coal mining is an important measure for prevention of gas outburst in China [1,2]. However, as the mining depth increases, the coal-rock mass permeability would decrease significantly, causing the difficulty of coalbed methane extraction [2,3]. To improve coal-rock mass permeability in deep underground coal mine, numerous hydraulic measures, including hydraulic slotting, high-pressure water injection, hydraulic punching and hydraulic fracturing, are proposed [2,4,5].…”

Section: Introductionmentioning

confidence: 99%

“…To improve coal-rock mass permeability in deep underground coal mine, numerous hydraulic measures, including hydraulic slotting, high-pressure water injection, hydraulic punching and hydraulic fracturing, are proposed [2,4,5]. Especially the hydraulic fracturing measure, it has been widely applied in engineering practice, but some failure cases of hydraulic fracturing in coal-rock mass which cannot achieve expected goals still exist [3,6]. The reasons are that there are many factors (e.g.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation on rules of fracture propagation during hydraulic fracturing in heterogeneous coal-rock mass

Yuan¹,

Shao²,

Xie³

et al. 2019

J. vibroeng.

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To investigate rules of fracture propagation during hydraulic fracturing in heterogeneous coal-rock mass, a new mathematical model for hydraulic fracturing with seepagedamage coupling and its numerical algorithm are proposed. The rules of coal-rock mass heterogeneity, confining pressure, beforehand hydraulic slotting, and non-symmetric pressure gradient on fracture propagation are investigated. Numerical results show the following: (1) Compared to homogeneous coal-rock mass, the fracture propagation pattern exhibits a more zigzag characteristic and the fracture initiation pressure is reduced in heterogeneous coal-rock mass. (2) Fracture propagation during borehole fracturing is mainly controlled by confining pressure ratio, and the fracture would propagate along the path with least resistance in coal-rock mass. (3) During hydraulic fracturing with beforehand hydraulic slotting, fracture propagation pattern would become more complex with slotting length increasing; the propagation direction of fracture is primarily controlled by principal stress difference, the larger of principal stress difference, the more difficult of oriented fracturing. (4) Non-symmetric pressure gradient can reduce breakdown pressure and influence fracture propagation pattern, which provides a beneficial guide for oriented fracturing. The simulation results are consistent with the theoretical solutions and experimental observations, which is promising to guide field operation of hydraulic fracturing to improve coalbed methane extraction.

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Numerical Modeling on Hydraulic Fracturing in Coal-Rock Mass for Enhancing Gas Drainage

Cited by 10 publications

References 27 publications

Similar Material Simulation Study on Protection Effect of Steeply Inclined Upper Protective Layer Mining with Varying Interlayer Distances

Similar Material Simulation Study on Protection Effect of Steeply Inclined Upper Protective Layer Mining with Varying Interlayer Distances

Numerical Simulation of Borehole Parameters for Coal Seam Gas Pre-Drainage

Numerical investigation on rules of fracture propagation during hydraulic fracturing in heterogeneous coal-rock mass

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