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 ...
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 .
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 ...
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 .
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 ...
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 .
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 ...
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 ...
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 .
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 ...
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 ...
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 .
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.
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.
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.
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 .
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 .
WEBMay 4, 2020 · Coal mining and production activities lead to static loading and unloading changes of coal stress in front of the working face, and the stress change process has a significant influence on the ...
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 ...
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.
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
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 .
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 .
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 ...
WEBSep 1, 2021 · For cyclic unloading, a lower unloading rate is beneficial to the compression of tectonic coal in the initial unloading stage. Previous experimental results have shown that the permeability of the ...
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.
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
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