Rules for confidence intervals of permeability coefficients for water flow in over-broken rock mass

Liu, Weiqun; Fei, Xiaodong; Fang, Jingnian

doi:10.1016/j.ijmst.2011.06.003

Cited by 24 publications

(6 citation statements)

References 8 publications

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“…Therefore, disintegrated coal seam in the ground form aquiclude (waterresisting) layers (e.g., [55]), which can be useful for groundwater protection as well as prevention of mining-induced groundwater influx. …”

Section: Discussionmentioning

confidence: 99%

“…The test results in this study showed that at a high compaction levels, the porosity of crushed and disintegrated coal decreases significantly, that results in considerable drop of the permeability value (e.g., about 16 times for uniform sample when porosity decreased from 0.34 to 0.19). Therefore, disintegrated coal seam in the ground form aquiclude (water-resisting) layers (e.g., [55]), which can be useful for groundwater protection as well as prevention of mining-induced groundwater influx.…”

Section: Discussionmentioning

confidence: 99%

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

Zhou

et al. 2017

Energies

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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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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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

Zhou

et al. 2017

Energies

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“…As a fact, a large number of seepage experiments under different loading modes have been conducted to evaluate the hydraulic evolution of the media under different stress states (Chen et al 2021;Liu et al 2012a;Tomlinson and Vaid 2000). Based on a transient seepage test under compress effect (Zhang et al 2016), it is found that the internal structure of KCP becomes looser under the influence of mining disturbance, so that the fine particles are more easily migrated.…”

Section: Experimental Studymentioning

confidence: 99%

A state-of-the-art review on rock seepage mechanism of water inrush disaster in coal mines

Duan

Zhang

et al. 2022

Int J Coal Sci Technol

103

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Water inrush is one of the most dangerous disasters in coal mining. Due to the large-scale mining and complicated hydrogeological conditions, thousands of deaths and huge economic losses have been caused by water inrush disasters in China. There are two main factors determining the occurrence of water inrush: water source and water-conducting pathway. Research on the formation mechanism of the water-conducting pathway is the main direction to prevent and control the water inrush, and the seepage mechanism of rock mass during the formation of the water-conducting pathway is the key for the research on the water inrush mechanism. This paper provides a state-of-the-art review of seepage mechanisms during water inrush from three aspects, i.e., mechanisms of stress-seepage coupling, flow regime transformation and rock erosion. Through numerical methods and experimental analysis, the evolution law of stress and seepage fields in the process of water inrush is fully studied; the fluid movement characteristics under different flow regimes are clearly summarized; the law of particle initiation and migration in the process of water inrush is explored, and the effect of rock erosion on hydraulic and mechanical properties of the rock media is also studied. Finally, some limitations of current research are analyzed, and the suggestions for future research on water inrush are proposed in this review.

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“…Hence, most experimental researches were carried out on the crushed rocks and fine clay particles to describe the seepage property of collapse column [7]. Liu et al [8] obtained the relation between the axial stress and the permeability of broken rock through the steady-state seepage experiment. In fact, the external axial stress affected the seepage behavior of broken rock by changing its structure such as fissure channels.…”

Section: Introductionmentioning

confidence: 99%

Seepage Property of Crushed Mudstone Rock in Collapse Column

Zhang

Lin

2020

Advances in Civil Engineering

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The karst collapse column composed of crushed rocks and fine argillaceous or clay particles is easy to form the fissure channels between the coal seam working face and the confined limestone aquifer under mining and causes water inrush disasters with the loss of underground water resource, economic losses, and casualties. It is of great necessity to understand the seepage properties of crushed rock in karst collapse column for the prevention of water inrush and the protection of underground water resource. A self-developed seepage test system is used in this paper to conduct laboratory experiments on seepage properties of crushed mudstone specimens. The effects of the particle size distribution, the porosity (specimen height), and the hydraulic pressure on the water flow velocity and the permeability of crushed specimen are analyzed. The results indicate that the permeability of specimen increases with the particle size, porosity, and hydraulic pressure. It can be known from the comparative experiments of progressive hydraulic pressure on one specimen and variable hydraulic pressure on different specimens with constant particle size and porosity that more fine particles leak out from the specimen with repeated application of hydraulic pressure on one specimen. Therefore, the permeability of one specimen is bigger than that of different specimens under the condition of same hydraulic pressure.

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Rules for confidence intervals of permeability coefficients for water flow in over-broken rock mass

Cited by 24 publications

References 8 publications

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

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

A state-of-the-art review on rock seepage mechanism of water inrush disaster in coal mines

Seepage Property of Crushed Mudstone Rock in Collapse Column

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