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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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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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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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 .
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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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WEBNov 1, 2023 · To further validate and promote the proposed damage constitutive model, the loadingunloading process of coal material is also simulated. Because energy is continuously transformed during loading, in the loadingunloading process, the damage variable is also defined by energy dissipation.
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WEBApr 1, 2017 · In underground operations, the coal cutter cut the coal seam, and large coal blocks were cut off from the coal wall. Then, the coal blocks were transported to the laboratory and processed into cylindrical specimens with diameters of 50 mm and lengths of 100 mm in accordance with the ISRM standard (Fairhurst and Hudson, 1999).The .
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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 ...
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WEBJun 28, 2023 · Some of the activities related to loading and unloading include: Loading. Loading involves the process of loading cargo into a transport vehicle, such as a truck or container. This involves efficiently and safely managing loads within the vehicle to prevent damage or loss during transportation. Demolition. Unloading is the activity of removing ...
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WEBFeb 8, 2019 · Rock burst is a astrophic dynamic disaster caused by sudden failure and instability of coal, loading paths play an important role in the failure of coal, the coal failure process is associated with charge exception information. Hence, violent coal failure mechanics and time–frequency domain distribution of charge signal such as rock burst .
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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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WEBMay 25, 2019 · To explore the differences in deformation failure and energy evolution and simulate the real excavation conditions of coal masses at different depths during the coalmining process, an unloading failure experiment was conducted. The experiment included coal samples at different depths from the no. 15 coal seam of the Ji group in the .
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WEBMar 29, 2024 · Conventional triaxial loading and unloading test scheme. A substantial amount of research indies that the stress distribution in the overlying strata in front of the coal face can be divided ...
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WEBOct 8, 2019 · Discussion on bulk carrier loading and unloading operations and freight safety for the owner's and master's responsibilities and obligations as per charter Party requirements. Master's Thesis, Department of Shipping Technology, National Kaohsiung University of Science and Technology, Kaohsiung, Taiwan, 2018.
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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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WEBJan 22, 2024 · Protective seam mining is the most economical and effective measure for eliminating coal and gas herniation. To study the unloading effect of the mining of a protective seam on the protected layer, and to better grasp the effect of the protective layer on the abatement, conventional triaxial tests were conducted on coal samples with the .
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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, 2014 · To comprehensively understand the differences in mechanical behavior of coal during the mining process at different depths, cyclic triaxial loading and unloading (CTLU) experiments with acoustic ...
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WEBApr 28, 2017 · During the postpeak loading and unloading process, the flow rate of the coal sample will decrease with the loading of confining pressure but increase with the unloading of confining pressure, and ...
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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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WEBJan 7, 2023 · By testing permeability during the loading and unloading process of coal samples, key parameters of the fractional permeability model were obtained to enter specific values into the model to ...
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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.
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WEBUnloading and loading freight happens so often that workers and management can become complacent to the inherent dangers that exist in the process. Unloading and loading freight is almost always under some sort of time constraint. This issue and tighter supply chain windows can exacerbate the problem and create an even more dangerous .
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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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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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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 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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WEBSep 24, 2022 · Effect of Cyclic Loading and Unloading on the Deformation and Damage Properties of Sandstone from Beizao, a Coal Mine underneath the Bohai Sea in China September 2022 Geofluids 2022(3):111
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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 ...
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WEBAug 1, 2019 · The results showed that the change trend of permeability was negatively correlated with the confining pressure in the process of loading/unloading of coal and it was divided into three stages for ...
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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 ...
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WEBOct 23, 2023 · Compared with the loading approaches mentioned above, the cyclic loading–unloading testament is an effective approach in revealing the mechanical response of coal and rock under repeated disturbance of excavation, 47, 50, 51 through parameters, such as peak strength, elastic modulus, and energy dissipation features. .
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