Characterization of the permeability and acoustic properties of an outburst-prone sandstone

Butt, Stephen; Frempong, Paul K.; Mukherjee, C.; Upshall, James

doi:10.1016/j.jappgeo.2005.04.002

Cited by 17 publications

(8 citation statements)

References 8 publications

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“…This model is an attempt to reproduce the phenomenon occurring during a rock and gas outburst in mine conditions, where the quantity of emitted gas is strongly dependent on its pressure and on the porosity of the rock and, in such a perspective, is proportional to the quantity of grains [ 13 ]. Based on given parameters of the rock–gas system, the program models the changing temperatures of the rock and gas.…”

Section: Experimental Methodologymentioning

confidence: 99%

See 1 more Smart Citation

The Intensity of Heat Exchange between Rock and Flowing Gas in Terms of Gas-Geodynamic Phenomena

Koziel

Topolnicki

Skoczylas

2021

Entropy

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Gas-induced geodynamic phenomena can occur during underground mining operations if the porous structure of the rock is filled with gas at high pressure. In such cases, the original compact rock structure disintegrates into grains of small dimensions, which are then transported along the mine working space. Such geodynamic events, particularly outbursts of gas and rock, pose a danger both to the life of miners and to the functioning of the mine infrastructure. These incidents are rare in copper ore mining, but they have recently begun to occur, and have not yet been fully investigated. To ensure the safety of mining operations, it is necessary to determine parameters of the rock–gas system for which the energy of the gas will be smaller than the work required to disintegrate and transport the rock. Such a comparison is referred to as an energy balance and serves as a starting point for all engineering analyses. During mining operations, the equilibrium of the rock–gas system is disturbed, and the rapid destruction of the rock is initiated together with sudden decompression of the gas contained in its porous structure. The disintegrated rock is then transported along the mine working space in a stream of released gas. Estimation of the energy of the gas requires investigation of the type of thermodynamic transformation involved in the process. In this case, adiabatic transformation would mean that the gas, cooled in the course of decompression, remains at a temperature significantly lower than that of the surrounding rocks throughout the process. However, if we assume that the transformation is isothermal, then the cooled gas will heat up to the original temperature of the rock in a very short time (<1 s). Because the quantity of energy in the case of isothermal transformation is almost three times as high as in the adiabatic case, obtaining the correct energy balance for gas-induced geodynamic phenomena requires detailed analysis of this question. For this purpose, a unique experimental study was carried out to determine the time required for heat exchange in conditions of very rapid flows of gas around rock grains of different sizes. Numerical simulations reproducing the experiments were also designed. The results of the experiment and the simulation were in good agreement, indicating a very fast rate of heat exchange. Taking account of the parameters of the experiment, the thermodynamic transformation may be considered to be close to isothermal.

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Section: Experimental Methodologymentioning

confidence: 99%

“…This problem is most often associated with coal mining [ 7 , 8 , 9 , 10 ]. However, beside coal mines, the risk of rock and gas outbursts also exists in potassium and salt mines [ 11 , 12 ] and in sandstone formations above coal strata [ 13 ].…”

Section: Introductionmentioning

confidence: 99%

The Intensity of Heat Exchange between Rock and Flowing Gas in Terms of Gas-Geodynamic Phenomena

Koziel

Topolnicki

Skoczylas

2021

Entropy

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“…The AE phenomenon occurs during the damage process of loading and unloading coal. 50,51 The AE is the sound wave emitted during the failure of the microcell inside the coal mass, which is obviously random and conforms to the Weibull distribution. Therefore, it can be used as an effective means to characterize the damage degree of the coal mass.…”

Section: Statistical Damage Model Of Mining-disturbed Coal Based On Dsrmentioning

confidence: 99%

Mining‐disturbed coal damage and permeability evolution: Model and validation

Cao

Wang

et al. 2021

Greenhouse Gases

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Coalbed methane (CBM) is not only the material cause of gas explosion and coal-gas outburst disasters during underground coal mining, but also a kind of clean energy. Coal permeability is an important parameter for CBM drainage. Although many coal permeability models have been developed in the past decades to describe the permeability evolution characteristics under elastic state, few of them could explain the permeability behavior of the mining-disturbed coal which is often the situation of CBM drainage during underground coal mining. The paper analyzed the mechanical factors affecting the damage-permeability characteristics of mining-disturbed coal, proposed the concept of the deviatoric stress ratio (DSR), and then established the statistical damage and permeability evolution models based on DSR. Results show that the deformation and damage of coal is controlled by the deviatoric stress and minimum principal stress. The plastic damage degree of coal mass becomes more serious with DSR increase, which leads to the improvement in permeability. The damage constitutive model was established based on the Weibull distribution function and DSR, and then the permeability model of mining-disturbed coal was built combining the Kozeny-Carman equation. The acoustic emission (AE) and permeability experiments of the loading and unloading coal sample were conducted. After normalizing and fitting the accumulative AE counts, the damage and permeability evolutions with respect to DSR were found out. The model-predicted permeability could match with the experiment results, verifying the reliability of the theoretical permeability model. The purpose of this paper is to provide a new approach for modeling damage and permeability of mining-disturbed coal based on DSR.

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“…show that the failure process of coal-rock combined body exhibits apparent AE characteristics that are significant when the specimen is initially damaged, yielded, and destroyed [42][43][44]. The AE characteristics in UCT with different gas pressures should be understood and interpreted to confirm the coal and rock fracture.…”

Section: Ae Dynamic Response Under Uct Previous Studiesmentioning

confidence: 99%

“…The experimental study on the mechanical properties of coal containing methane was performed on raw coal samples in a coal mine located in Guizhou Province, China. AE system choice of high precision equipment from PAC (Physical Acoustic Corporation), the parameters of AE device were set as follows: main amplifier, 40 Hz; threshold value, 35 db; sensor resonant frequency, 20-400 kHz; sample frequency, 1 MHz (more details about this system and parameters can be seen in [43][44][45]). Figure 2 clearly shows that the AE event count changes with loading stress in different stages.…”

Section: Ae Dynamic Response Under Uct Previous Studiesmentioning

confidence: 99%

An Experimental Investigation on the Relationship between MS Frequency Response and Coal and Gas Outburst

Zhu

Li²,

Feng

et al. 2018

Shock and Vibration

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Microseismic (MS) frequency response is an important part of high-efficiency data mining to achieve the aim of coal and gas outburst (CGOB) early warning. Based on the variation pattern of acoustic emission (AE) signal in the coal failure process, the experimental characteristics of MS activity and typical signals CGOB were obtained in this study. First, the AE behavior of coal failure experiment was studied, and an explanation of laws was provided as follows: the fracture behavior of coal sample exhibits certain characteristics of AE response in terms of AE event count, signal amplitude, and frequency; each stage has its own physical meaning during the process of loading test. Based on these laws, CGOB experiments were carried out using a large CGOB physical simulation system with a MS monitoring system. Notching filter and wavelet packet transform technique were used in the denoising and feature extraction of six typical MS events (signals). The features of each stage, including the time-frequency domain, were extracted and quantitatively expressed. We finally arrive at the following conclusions: (1) CGOB exhibits significantly periodic characteristics, and each CGOB stage corresponds to the significant response characteristics of MS. CGOB presents varying characteristics, such as "valley-peaks-valley". (2) From the incubation stage to happen stage of outburst, the spectrum significantly moved from extremely low frequency (100-200 Hz) to high-frequency band (approach to 1600 Hz). During the residual stage, MS frequency manifested the concentration distribution (50 Hz) and offered the advantage of energy concentration. (3) The phenomenon of signal energy also shows the trend of energy transform low to high and to low modes along with the process. Signals total energy distribution (42.81%, 1,437.5-1,812.5 Hz) in the happen stage are markedly larger than those of events in incubation stage (7.01%) and residual stage (1.44%). The methodology presented in this paper for CGOB signal analysis provides a new method to obtain MS response precursor and predict CGOB disaster. This approach can be useful for rockburst anticipation and control during mining in gas and highly stressed coal mines.

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Characterization of the permeability and acoustic properties of an outburst-prone sandstone

Cited by 17 publications

References 8 publications

The Intensity of Heat Exchange between Rock and Flowing Gas in Terms of Gas-Geodynamic Phenomena

The Intensity of Heat Exchange between Rock and Flowing Gas in Terms of Gas-Geodynamic Phenomena

Mining‐disturbed coal damage and permeability evolution: Model and validation

An Experimental Investigation on the Relationship between MS Frequency Response and Coal and Gas Outburst

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