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 .
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WEBFeb 1, 2019 · the pressure loading and unloading process was explained theoretically based on a tight fourparticle packing unit, whic h provides a reasonable explanation for the experimental results
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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 ...
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WEBJun 1, 2020 · As the coal body has a hysteresis effect during the unloading process, it cannot be unloaded to 0 when unloading, and the minimum unloading level was set for the four kinds of samples; that is, after unloading to 2% σ c, the loading was performed until the sample was destabilized.
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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 .
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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.
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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 ...
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WEBDec 15, 2023 · Then, gas seepage tests of the coal rock damage process with different hydrostatic pressure and gas pressure conditions under triaxial stress loading–unloading were carried out. Finally, the model was verified based on the experimental results of this paper and other studied presented in the literature, and the verifiion results were ...
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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 ...
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WEBSep 1, 2018 · However, the loading and unloading rates have an important influence on the mechanical properties of the coal, and are closely related to the excavation steps of the working face. During an actual excavation process in a coal mine, the coal miners often reduce the excavation steps in order to prevent coal and gas outburst.
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WEBJun 26, 2023 · Coal mining often causes periodic disruption in the rock mass around the stope. The study of the deformation and failure characteristics of cyclic loading and unloading sandstone is very critical for gaining a thorough understanding of the mechanisms of rock damage, degradation, and failure. This kind of investigation is very .
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WEBFeb 1, 2024 · In the process of coal seam mining, the coal is disturbed by periodic pressure. This disturbance can be simplified to the loading process under different stress environments [5], [9], [10], [45], and the characteristics of the mining stress path are different under different advancing speeds [46]. Fig. 3 shows the loading path of the .
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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 ...
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WEBAug 20, 2022 · The strain of coal mainly occurs in the first loading process. Compaction occurs largely during the loading process, and the fracture closure during this stage is mainly irreversible plastic deformation. The volume and morphology of the sample after unloading cannot be fully restored to the situation at the initial loading stage.
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WEBJun 1, 2020 · In the loadingunloading tests, the PER value was calculated based on the initial porosity and the relative increment in the volumetric strain during the whole loadingunloading process. A lower ...
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WEBMar 20, 2023 · In the process of coal formation, the internal structure is different from the occurrence of primary cracks. As a result, the new crack generation and primary crack development of different samples are affected to different degrees during loading and unloading. Energy characteristics under true triaxial loading and unloading
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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 .
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WEBFeb 9, 2024 · Horizontal well cavern completion and stress release is considered a potential technique for efficient development of coalbed methane in tectonically deformed coal (TDC). Pulsating loading and unloading is a key technique for the controlled expansion of caverns and broader stress release within the reservoir. However, current understanding .
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WEBThe permeability characteristics of a broken coal mass under repeated loading and unloading conditions exert significance on spontaneous combustion of coal in goaf during the mining of coal seam groups. Considering this, by using the seepage test system for broken coalrock mass, seepage tests under cyclic loading and unloading .
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WEBDec 1, 2020 · Fig. 9 shows that coal rocks with fracture networks of different levels of complexity all undergo essentially the same permeability evolution process under loadingunloading conditions, although differences in the final increase in permeability can be observed. The higher the complexity of the initial fracture structure is, the higher the final ...
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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 .
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WEBJan 1, 2011 · Introduction At present, coal is the preeminent fuel of thermal power plant. Continuing up the large unit, and large capacity, the demand of coal is very large. Coal need to process from loading and unloading to stockpile, this procedure can finish by coal conveying system.
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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.
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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 ...
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WEBFeb 27, 2023 · The damage and fracture of coal is accompanied by a complex energy conversion process, and these different stages of energy evolution are closely related to coal failure. In this paper, an evolution model describing the behavior of coal failure was proposed using the energy dissipation under cyclic loading/unloading. The energy .
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WEBJan 23, 2021 · On the premise that the point of the maximum abutment pressure is the demarion point of gas migration, an experimental research was conducted on gasbearing coal by using a thermofluid–solid coupling test system. The research results demonstrate that irreversible strain and elastic modulus increase with increase in .
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WEBJan 22, 2024 · Su 21 studied the AE and damage characteristics of coal and rock under cyclic loading. ... There is an energy conversion process for loading and unloading rocks. Based on the principle of energy ...
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WEBJul 31, 2017 · The repeated mining causes the unloading and loading of the caved zone, so that the pore structures of caved zone change accordingly, and thus affect the permeability value, which controls the gas migration in the caved zone. The main factors affecting the permeability of the unloading process are different from those controlling .
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WEBNov 12, 2020 · Stressstrain curves of coal from unloading tests under different confining pressures As shown in Fig. 5, the recovery of deformation and permeability occurs in the coal sample with the unloading ...
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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.
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WEBJun 1, 2015 · Fig. 3 (a) compares the deviatoric stress–strain complete process in coal I under both constant and unloading confining pressures. Fig. 3 (b) plots the complete process of coal II under only unloading confining pressure. Firstly, the deviatoric stress–strain complete process is observed to be almost identical before the loading .
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WEBNov 30, 2018 · Moreover, pressure relief mining produces loading and unloading processes in the protected coal seam, and we also find the permeability heavily depends on the loading or unloading process, ...
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WEBOct 15, 2022 · Under the stress loading condition, the coal matrix and fractures of PUC samples were compressed simultaneously, and the permeability was regulated by the porefissure structures in the coal matrix. ... Research on the permeability response characteristics of the stress loadingunloading process can provide some clarifiions .
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