WEBDec 15, 2023 · A novel permeability model under triaxial pressure loading–unloading was developed. • The influence of effective stress and adsorption/desorption is considered in model. • The model is verified using test results of coal seepage under three conditions. • Triaxial pressure loading–unloading has a significant effect on coal permeability.
WEBJun 1, 2019 · (3) During the loadingunloading process of confining pressure, the permeability of coal containing gas is damaged to a certain extent and this damage can be represented by the maximal damage rate ...
WEBNov 15, 2018 · Abstract and Figures. In this article the process of coal unloading from the face's fracture zone to the conveyor using shearer drums is presented. The effect of the form and dimensions of the ...
WEBApr 1, 2024 · During the loading process, the common loading method is constant displacement loading, such as mm/min, etc. ... 2019c, Zhang et al., 2019d studied the effect of three cycles of loading and unloading on the permeability of broken coal sample based on the impact of multiple loading and unloading on the goaf during the mining .
WEBAug 12, 2021 · The coal burst is a violent failure process induced by unloading the coal seam which had been subjected to the high insitu stresses. During the unloading process, the energy stored in the coal seam and surrounding rock release rapidly, usually leading to rock burst. ... Many factors can trigger the coal burst,, the dynamic load .
WEBJan 9, 2017 · various loading conditions, an ultrasonic test system f or the deformation and fracture of coal rock was used and a cyclic loading and unloading pattern is adopted.
WEBFeb 20, 2020 · Loading and Unloading Elastic Modulus. Coal is a porous medium that is affected by the geologic environment during the formation process. Coal contains a large number of primary pores and microcracks, resulting in coal being a .
WEBSep 1, 2021 · Only by superimposing the two values can the real dissipated energy of coal be obtained. In the process of unloading and loading confining pressure, the axial dissipated energy can be expressed as: (13) U d 1 = W 1 − E e 1 = σ 1 ′ ∫ d ε 1 − − ∫ d ε 1 + where ε 1 − and ε 1 + are the axial strain values in the confining ...
WEBFeb 15, 2014 · By using RMT150B rock mechanics test equipmentthe acoustic emission(AE)tests of coal specimen under conventional triaxial and triaxial cyclic loading and unloading were carried outand AE characteristics of coal specimens under different loading situations was test results show that the AE mutation point in .
WEBOct 31, 2019 · During the loading/unloading process, the gas pressure in the coal sample is maintained constant through the ingenious structure design of the system. As shown in Fig. 2 b, the constantvolume chamber is connected to the sample by a gas tube, and the constantvolume pistons are connected to the axial indenter.
WEBDec 12, 2021 · 1. Introduction. With an increase in the coal mining depth, the influence of high insitu stress and high osmotic pressure on the pore structure and the permeability of surrounding rocks of the coal body in working faces has been increasingly investigated. 1 For deep underground engineering, due to the action of severe disturbances such as .
WEBNov 18, 2022 · The results of cyclic loading–unloading experiments demonstrate that there is a correlation between the damage process caused by moisture content and stress in coal samples, and the evolution of dissipation energy and the development of hysteresis loops are both related to the presence of the characteristic stress σ'. The RA–AF ster ...
WEBApr 18, 2024 · The loading process can be divided into four stages, as seen in Fig. 6 a: (1) initial loading, (2) unloading of σ 3, (3) stress concentration, and (4) the coal burst stages. The initial stress level was applied by multistage loading (the initial stress σ 0 has three grades). When the stress reaches the designed value, it will remain constant ...
WEBOct 10, 2022 · Permeability changes with confining stress loading–unloading: (a) is the PUC; (b) is the aclastic coal; (c) is the mylonitic coal; (d) is the loading–unloading process of confining stress. The increase in confining pressure compressed the coal matrix and internal fissures of the coal cores, and their permeability rapidly and then slowly ...
WEBMay 27, 2022 · The loading process of CRCS under biaxial compression experienced four ... which has resulted in the rapid unloading of stress in coal and rock. A high unloading speed of 10 m/s of horizontal stress was used to investigate the effects of a much higher unloading speed on the failure and instability of the CRCS according to the speed set ...
WEBSep 1, 2017 · From the perspective of mechanics, coal mining is a loading and unloading process. The typical underground loading and unloading features are mainly distributed on the front side and the protective layer. These loions are often in a complex stress environment. The main variation of the force is shown in Fig. 1. It shows that the force ...
WEBOct 26, 2023 · This indies that during the whole cyclic loading and unloading process under confining pressures, the sample can maintain good elastic properties in the direction of the maximum principal stress. ... Chen HD, Cheng YP, Zhou HX, Li W (2013) Damage and permeability development in coal during unloading. Rock Mech Rock Eng .
WEBJan 1, 2018 · During the process of deep coal mining, coal seams are generally under the true triaxial stress state (σ1>σ2>σ3), which is influenced by the crustal stress and strong excavation disturbance.
WEBJun 1, 2019 · The fitting formulas of coal sample axial and radial permeability values under three loading/unloading cycles are shown in Table 5. In Table 5, subscripts A and R respectively denote the axial and radial permeability of coal samples; L and U denote loading and unloading, respectively; and 1, 2, and 3 refer to the number of .
WEBSep 1, 2020 · The energy evolution and fragment distribution characteristics of different types of rocks were investigated through the uniaxial cyclic loading and unloading experiments for granite, redsandstone, coal, gypsum, and highwater material. Based on the results of the study, the following conclusions are drawn.
WEBMar 7, 2021 · In coal mining activities, the abutment stress of the coal has to undergo cyclic loading and unloading, affecting the strength and seepage characteristics of coal; additionally, it can cause ...
WEBNov 20, 2022 · The paper represents a test investigation of the mechanical properties and acoustic emission (AE) characteristics of lowstrength coal specimens subjected to cyclic loading and unloading. From the lab tests, the following conclusions can be obtained: (1) The axial strain is very well linear with the loading–unloading cycle number, and the .
WEBMar 12, 2023 · The load–unload tests of coalrock combination were carried out in this study, and the specific setting is as follows: Scheme I conventional triaxial compression test. ... In addition, in the process of unloading confining pressure, the axial strain of the sample changes little before failure, and it starts to increase significantly when ...
WEBSep 1, 2022 · The mining of coal resources causes the stress on the front and both sides of the working face to be in a complex loading and unloading process, and the gas contained in the coal body migrates ...
WEBAug 1, 2022 · In the cyclic loading and unloading process, the load ing and unloading elastic modulus of coal samples experi ences a rapid increase at the beginning stage of the cyclic
WEBSep 26, 2023 · The rock mass in fault zones is frequently subjected to cyclic loading and unloading during deep resource exploitation and tunnel excavation. Research on the mechanical and hydraulic characteristics of fault rock during the cyclic loading and unloading is of great significance for revealing the formation mechanism of water .
WEBJan 1, 2020 · In the coal mining process, the stress state of the coal seam will change due to unloading caused by coal mininginduced, which may lead to the occurrence of coal and gas outburst disasters.
WEBSep 1, 2017 · The mining of coal resources causes the stress on the front and both sides of the working face to be in a complex loading and unloading process, and the gas contained in the coal body migrates ...
WEBIn the excavation process, the coal pillar will undergo shear failure due to repeated loading and unloading from mining stress. Meanwhile, plastic flow will occur after shear failure. The permeability change of the coal pillar under plastic flow is closely related to the loading path. Through a permeability test of the coal sample after shear yielding under .
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