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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The residual strains has produced by the first loadingunloading of coal are 7 × 10 −5, × 10 −4, and × 10 −4, respectively. ... However, if the loadingunloading process was continued beyond this point, the residual strain reappeared. The occurrence of the nonresidual strain phenomenon was found to be directly related to the ...
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Permeability changes with confining stress loadingunloading: (a) is the PUC; (b) is the cataclastic coal; (c) is the mylonitic coal; (d) is the loadingunloading 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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CAMTECH and RDSO to identify equipments which could be used for unloading coal ... During the process wagons are getting damaged due to following action of the ... Loading/unloading machines can be divided on the basis of dumping height and type of bucket. The equipment with a dumping height of about feet are called Dumpers or
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Both coal companies and Railways have envisaged to jointly ensure per day coal loading of 415 rakes of domestic coal and 30 rakes of imported coal to the power sector. 'In the current month ...
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Thus, the axial stress in the experiment is equal to the confining stress. In this study, three loading and unloading seepage tests have been carried out to simulate the effect of three coal seams mining on the caving zone and the second and third loading and unloading stress paths are the same as the first loading and unloading stress path.
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The loadingunloading process is represented as follows: 0 ... In cyclic loading process, the coal samples first exhibit the appearance of microcracks at the beginning stage. With the increase in the axial stress, the damage gradually accumulates and produces irreversible plastic deformation. When the peak load is reached, partial area of ...
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in the study of the inuence of dierent loading and unloading rates on the coal body under the unloading path, it is often only considered to change the axial loading rate or only change the conning pressure unloading rate. The deformation and failure laws of coal under dierent loading and unloading rates are rarely systematically compared and
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During the process of underground mining, roadway excavation and heading face cause the surrounding rock to produce stress disturbance and break the equilibrium state of coal and rock, which is usually manifested as axial loading and confining pressure unloading. This phenomenon is more obvious during the deep mining of coal and rock.
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The size effect of coalgangue mass after loading and unloading test is the reflection of its inherent structural complexity, which is due to the existence of fracture network system in rock mass and the joint influence of loading and unloading process. Coalgangue physical and mechanical properties and particle distribution, as well as defects ...
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In the unloading process, the fracture space in coal sample extends and expands passively, instead of the compression of fracture under stress loading. The microcracks and beddings in the coal sample gradually connect, the number of gas permeation channels increases, and the rate of gas transport within coal becomes faster.
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Coal mining leads to stress loadingunloading variation in front of the working face, which influences the occurrence of disasters. In order to study the influence mechanism of stress loadingunloading to the coal failure, a series of experiments of gasbearing coal deformation and failure under triaxial stress were conducted and acoustic emission (AE) was monitored.
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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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Given the roadway deformation and surrounding rock control in the process of thin coal seam mining, the coalrock combination with inclination angles for 0°, 15°, 30°, 45°, and 60° was designed. The rock mechanic test machine was used to conduct a uniaxial compression test and a graded loading and unloading test on the coalrock combination; the failure characteristics of the two were ...
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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, which can cause gasdynamic disasters in severe cases.
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The coils are then loaded either on a reel style or cradle style uncoiling system. Cradle style uncoilers are relatively easy to load, you basically lower your coil onto the cradle, position the sides guides to center the coil and your coil is ready to be released. On a reel type the process is not as easy. You have a large heavy object either ...
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To investigate the influence of loadingunloading paths as well as loading and unloading rates on the deformation and failure behavior of coal, laboratory experiments and numerical simulations of unloading under axial pressure and confinement were carried out. The effect of different axial loading rates and unloading rates on the deformation and failure behavior of coal under the unloading ...
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The loading and unloading rate for uniaxial and cyclic fatigue load were mm/min. The Express8 AE monitoring system was adopted to continuously log the acoustic events/micro failure inside the coal samples during the whole loading process.
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Coal is an important, widelyused source of energy and a chemical raw material, which is transported globally in large quantities; more than a billion tonnes of coal per year are transported by sea (IEA International Energy Agency, 2020). However, its carriage as a cargo is associated with a number of hazards and coal must be carried in ...
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Ship Cargo Handling, Loading, Unloading: A commercial ship is usually a link in a "trade route" between distant points. Goods flowing in the route must be transferred to and from the sea link; they must also be given care while aboard the ship, and in turn they must not be a hazard to the ship and its crew. Ancient cargo handling consisted almost exclusively of manually carrying cargo in ...
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The D s characterizes the effect of a single loadingunloading cycle on a coal body permeability transformation. During the stress unloading process, the pore spaces in a coal body expand after it is unloaded from the highstress environment. The original fractures in a coal sample reopen during the effective stress reduction.
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The process of rock cycle loading and unloading results in the external force constantly performing work on the specimen. The external force is converted into elastic strain and dissipation energy. Using the principles of thermodynamics, energy transformation is the essential process by which the energy state of the specimen changes, as ...
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