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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WEBDec 20, 2021 · In the true triaxial cyclic mechanical experiment of coal, most of the total work done by the three principal stresses is accumulated in the coal with elastic potential energy (the elastic strain energy will be released in the unloading process of external force, approximately equal to the negative work done by the external force in the ...
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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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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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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 .
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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 ...
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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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WEBSep 19, 2023 · This paper presents two experimental schemes, graded cyclic loading and unloading, and variable lower limit cyclic loading and unloading, to investigate the energy evolution and acoustic emission characteristics of rocks under different cyclic loading and unloading paths. The experiments were conducted using a WAW300B microcomputer .
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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 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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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 ...
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WEBJul 11, 2022 · The change of elastic modulus of coal samples with the moisture. content of % is the largest in the first and sixth cyclic loading–unloading, decreasing. Mpa and Mpa ...
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WEBApr 5, 2021 · For example, in the loading and unloading process, much elastic energy accumulates in the coal and rock mass with increasing elastic deformation. Under unloading, elastic energy is released. In the test process, the total energy density and elastic energy density of the coal mass can be expressed as Formulas ( 2 ) and ( 3 ).
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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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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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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 ...
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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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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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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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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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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 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 7, 2024 · 5. Signage and Communiion: Clear and visible signage plays a crucial role in promoting safety during loading and unloading activities. Signage should indie designated loading zones, maximum load capacities, and potential hazards. Effective communiion between workers, drivers, and other personnel involved in the process .
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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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WEBMar 16, 2023 · Research on the mechanical properties and damage evolution of coal during true triaxial cyclic loading and unloading is of great significance for maintaining the longterm safety and stability of underground engineering structures in coal mines. In this paper, firstly, the deformation, strength and fracturing characteristics of coal during true triaxial .
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