Variations of hydraulic properties of granular sandstones during water inrush: Effect of small particle migration

Ma, Dawei; Rezania, Mohammad; Yu, Hai‐Sui; Bai, Haibo

doi:10.1016/j.enggeo.2016.12.006

Cited by 210 publications

(101 citation statements)

References 31 publications

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“…e parameters of permeability and porosity play an important role in the study of accumulation and development of coalbed methane [2][3][4]. To increase the permeability of those coal seams, underground hydraulic fracturing technology to transform the seam structure is an effective way to achieve this goal [5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

An Elastoplastic Softening Damage Model for Hydraulic Fracturing in Soft Coal Seams

Yang

Mao

et al. 2018

Advances in Civil Engineering

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In order to improve the permeability of soft coal seams with low intensity and permeability by hydraulic fracturing, an elastoplastic softening damage model of soft coal seams has been established, which takes into consideration the lower elastic modulus and tensile strength and higher pore compressibility and plastic deformation. e model then was implemented to FLAC3D finite difference software to be verified with the on-site results of the Number 2709 coalface in Datong coal mine, China. e modelling results of fracture-influenced radius show good consistency with on-site results. en the parameters of water injection rate and time on fracture-influenced radius were studied. e results indicate that the fracture-influenced radius increases rapidly with an increased injection rate initially. After reaching the maximum value, fracture-influenced radius decreases slowly with further increase of the injection rate. Finally, it remains constant. e fracture-influenced radius rapidly increases initially at a certain time and then slowly increases with the injection time. e novel model and numerical method could be used to predict the radius of hydraulic fracture-influenced area and choose the suitable injection parameters to help the on-site work more efficiently.

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Section: Introductionmentioning

confidence: 99%

An Elastoplastic Softening Damage Model for Hydraulic Fracturing in Soft Coal Seams

Yang

Mao

et al. 2018

Advances in Civil Engineering

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“…Because the differential equations for deflections (12) and (13) are identical to that of the corresponding zones reported in literature [20], the solution form of the differential equation for the deflection of semi-infinite elastic foundation beam in zone (−∞, 0] is the same as reported in the literature [20], and it is denoted as follows:…”

Section: Deflection Equations and Continuitymentioning

confidence: 88%

“…For a hard roof with advanced fracture, when the working face advances to below the roof fracture line, if the supporting resistance of frame and friction between seams are insufficient, the roof easily subsides in a stepped style, causing collapse accidents under pressure and even rock burst disasters. Many studies have been conducted on the deformation, law of motion, and fracture of a hard roof under the overlying load by field observation, similar material simulation, numerical simulation, and theoretical analysis [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Qian et al [15,16], Miao et al [17], and Li et al [18] analyzed a hard roof by assuming the support pressure relationship between coal seam and immediate roof as an elastic foundation and obtained some basic results such as the deflection solution for a hard roof and the maximum bending moment in the front of a coal wall and for an advanced roof fracture.…”

Section: Introductionmentioning

confidence: 99%

Bending Moment Characteristics of Hard Roof before First Breaking of Roof Beam Considering Coal Seam Hardening

Jiang

Pan

et al. 2018

Shock and Vibration

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The mechanical properties of a coal seam affect the distribution of support pressure. Considering the strain hardening effect of coal seam, the support pressure relationship of three zones-softened, hardened, and elastic-of a coal seam with regard to a hard roof is proposed, and methods to determine an approximate expression for the support pressure of hardened zone of coal seam, the range of hardened zone, and the corresponding peak values of support pressure are provided. The deflection equations of a hard roof under three different support pressure relationships of coal seam before the first breaking were theoretically derived, and all the relevant integration constants were determined. Numerical examples of two cases are provided for calculating the bending moment of a hard roof and the support pressure of a coal seam. The analysis shows that as the working face advances, the maximum support pressure increases, the residual strength of coal seam at coal wall decreases, the overall deflection of roof gradually increases, the maximum bending moment of roof in the front of coal wall increases, and the advanced distance of roof bending moment peak gradually increases. As the depth of softened zone of coal seam increases, the similar conclusion is obtained, and the advanced distance of the roof bending moment peak increases at a relatively fast speed. Because the bending moment peak of hard roof is located near the support pressure peak in the softened zone of coal seam, the depth of softened zone of coal seam significantly affects the advanced distance of the bending moment peak of a roof. The actual advanced fracture distances of hard roof are distributed in a relatively broad range. The results indicate that there is a "large and long" type advanced fracture distance occurring in the actual stope. With the same overlying load and stope parameter conditions, the maximum support pressures of support roof in softened, hardened, and elastic zones considering a hardened coal seam are smaller than those in softened and elastic zones without hardening. However, the plumpness in front of the peak of the former support pressure curve is superior to that of the latter, and both the bending moment peak value and the advanced distance of bending moment peak of the former are higher than those of the latter.

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“…After mining operations, along with the consolidation process around the excavated areas, a state of equilibrium can be reached within the disturbed zones [43]. In these mining-affected areas, in addition to the investigation of the geological formations, water table and cavitation percentages of underground openings [44][45][46][47], it is also essential to study the hydraulic properties of the deformed rocks under the constant loading of the overlying ground layers [48]. As a practical issue in mining geotechnics, studying the compaction and hydraulic conductivity attributes of deformed strata makes a great contribution to plan for mitigation of potential problems that can arise from mining activities.…”

Section: Experimental Conditionsmentioning

confidence: 99%

Grain Size Distribution Effect on the Hydraulic Properties of Disintegrated Coal Mixtures

Zhou

et al. 2017

Energies

Self Cite

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Abstract:In order to better understand groundwater influx and protection in coal mining extraction works, an in-house water flow apparatus coupled with an industrial rock testing system, known as MTS 815.02, were used to study the effects of grain size mixtures on the compaction and flow properties of disintegrated, or non-cemented, coal samples. From the Reynolds number evaluation of the samples with different grain mixtures, and the relationship between the water flow velocity and pore pressure gradient differences, it was found that seepage through the mixtures are of non-Darcy flow type. The porosity of coal specimens was found to be highly affected by compaction, and the variations of the porosity were also influenced by the samples' grain size distribution. It was found that the sample porosity decreases with increasing compaction and decreasing grain sizes. Grain crushing during compaction was observed to be the main cause of the appearance of fine grains, and the washing away of fine grains was consequently the main contributing factor for the weight loss due to water seepage. It was observed that during the tests and with the progression of compaction, permeability k decreases and non-Darcy factor β increases with decreasing porosity φ. The k-φ and β-φ plots show that as the sizes of disintegrated coal samples are getting smaller, there are more fluctuations between the porosity values with their corresponding values of k and β. The permeability value of the sample with smallest grains was observed to be considerably lower than that of the sample with largest grains. Non-Darcy behavior could reduce the hydraulic conductivity. It was found that the porosity, grain breakage and hydraulic properties of coal samples are related to grain sizes and compaction levels, as well as to the arrangement of the grains. At high compaction levels, the porosity of disintegrated coal samples decreased strongly, resulting in a significant decrease of the permeability at its full compression state; Non-Darcy flow behavior has the slightest effect in uniform samples, therefore, indicating that disintegrated coal in uniform grain size mixtures could be treated as an aquicluding (water-resisting) stratum.

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Variations of hydraulic properties of granular sandstones during water inrush: Effect of small particle migration

Cited by 210 publications

References 31 publications

An Elastoplastic Softening Damage Model for Hydraulic Fracturing in Soft Coal Seams

An Elastoplastic Softening Damage Model for Hydraulic Fracturing in Soft Coal Seams

Bending Moment Characteristics of Hard Roof before First Breaking of Roof Beam Considering Coal Seam Hardening

Grain Size Distribution Effect on the Hydraulic Properties of Disintegrated Coal Mixtures

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