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 .
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 .
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 .
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 ...
WEBJun 1, 2015 · To simulate the unloading process of cemented backfill in the deep highland environment of coal mine, triaxial unloading confining pressure tests of cemented coal gangue fly ash backfill at different unloading rates after curing at different temperatures (20 ℃, 35 ℃ and 50 ℃) were carried out by the Rock Triaxial Testing System, and the ...
WEBFeb 1, 2021 · The samples collected from Banxi coal mine in Chongqing, Southwest China, have been used to study on damage of coal based on permeability change rate (PCR) and loadunload response ratio (LURR ...
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 ...
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.
WEBThe occurrence of coal–rock dynamic disasters is determined by mininginduced stress loading and unloading. Therefore, it is of great significance to analyze the precursory information of coal deformation and failure during true .
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.
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 .
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, 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 ...
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.
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 ).
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 .
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 .
WEBNov 1, 2023 · Coalrock combinations is a composite structure often encountered in mining engineering. At present, the research on coalrock combinations mainly focuses on the loading mechanical properties. However, when mining engineering involves excavation, the mechanical characteristics of the coalrock combination during unloading are very .
WEBAbout Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright ...
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 .
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 ...
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 .
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.
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.
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 .
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 .
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 .
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 .
WEBMay 14, 2024 · This study investigates the stability of an artificial dam used in an underground reservoir in a coal mine under periodic weighting imposed by overlying rock strata. For this purpose, cyclic loading and unloading tests with different stress amplitudes were designed. Differences in the mechanical performance of the artificial dam with and .
WEBResearch on energy and damage evolution patterns of gascontaining coal under constricting pressure unloading conditions is urgently needed in the process of deep underground mining and is crucial for understanding the mechanisms underlying coal and gas composite rockburst occurrences. Prior reaching peak stress, cyclic loading and .
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 .
WEBDec 1, 2019 · This loadingunloading process can also occur in roomandpillar mines as the cascading pillar failure occurs. Fig. 1 (c) shows a series of gascontained pillars each subject to the same tributary area loading. If one of the weak pillars fails (Fig. 1 (c1)), the load will transfer to neighboring pillars causing an abrupt pillar loading .
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
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 .
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 ...
© DZCrusher - كل الحقوق محفوظة
