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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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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A scheme of the uniaxial cyclic loading and unloading tests is shown in Fig. 2b. The test process used the displacement control method, and the loading and unloading rate was mm/min, with 6 ...
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Conventional and cyclic unloading tests with different unloading rates were conducted to study the influences of unloading patterns and rates on the deformation characteristics and mechanical properties of tectonic coal. The results demonstrate that, under continuous unloading, a lower unloading rate promotes an increase in the circumferential strain but inhibits increases in axial strain.
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For unloading, cranes with grabs are the norm, although specialised equipment may be used for certain cargoes. When vessels unload using cranes and grabs, personnel and vehicles are often placed inside the holds to assist the process. Cargo is usually unloaded into hopper barges, then transferred by conveyor to silos or open storage.
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True triaxial loadingunloading tests of coal samples were performed using a multifunctional true triaxial fluidsolid coupling experimental system. The deformation, seepage, damage, strength, and failure characteristics of the coal samples were analyzed. Based on this, the variation mechanism of the permeability and yield conditions under different gas pressures was investigated, and the ...
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The effects of repeated loading and unloading paths on the raw coal samples were studied by analyzing the samples' permeability, energy dissipation and AE characteristics. ... During the loading and unloading process, the work done by the effective confining pressure on coal mass is far smaller than that of the axial effective stress ...
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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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Coal isn't carrying the burden for other commodities anywhere except on the subdivisions that are almost nothing but coal. At present, coal supplies % of electricity, nuclear %, natural gas %, oil %, hydro %, and other sources (mostly biomass, but also wind, geothermal, and solar) about %.
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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 damage in coal cyclic loading was quantitatively characterized by the damage variables and damage constitutive equations based on electrical resistivity. The results show that the response of resistivity and DIC is regular and complementary. ... The results show that during the true triaxial cyclic loading and unloading process, the ...
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The underground coal mining process is closely associated with frequent energy storage and consumption of coal mass with natural and induced fractures. Exploring the energy evolution characteristics of intact and fractured coal samples could be helpful for dynamic disaster control. In this study, laboratory true triaxial tests on the energy evolution characteristics of intact and fractured ...
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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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Scholars have examined the mechanical 22,23, the damage 24,25, and the energy characteristics 26,27 of coal under cyclic loading and unloading. In the process of cyclic loading, some scholars ...
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Fig. 3 presents the influences of gas pressure on coal permeability during gas loadingunloading processes at temperatures of 30 °C, 40 °C, 50 °C, 60 °C, and 70 °C, respectively. In the loading process, the coal permeability decreases gradually. As the pore pressure rises from MPa to MPa, the coal permeability decreases rapidly.
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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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In order to attain high efficiency, carefully matched loading and unloading terminals are necessary. In one example, a unit train transporting 17,400 tons per 1,200kilometre round trip from mine to plant has a turnaround time of 72 hours—including a 4hour loading and 10hour unloading and servicing time per train. Onhighway trucks
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The working process of the underground coal bunker was actually the loading or unloading of coal for the silo wall. And the stress environment of the silo wall and surrounding rock continually changes, resulting in the deformation of the silo wall under the inner lateral pressure. Stress Analysis
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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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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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As a result, the crack of saturated coal samples cannot keep stationary in the initial stage of loading and unloading and it slips throughout the loading and unloading process. A large number of macrotensile cracks appeared in the failed coal samples with pore water, as the pore pressure provides tensile force to the cracks and promotes the ...
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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 it during loading.
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To study the weakening process, deformation, and failure characteristics of rock masses surrounding deep chambers under complex stress environments, triaxial loading tests along with triaxial loading/unloading followed by uniaxial loading tests were conducted on sandstone specimens. The internal microcracks of the specimens under the loading and unloading of triaxial confining pressure were ...
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to start at full load. Coal handling system for modern power plants Tanjung Bin Power Plant with 3x700 MW, located in the southern state of Johor, Malaysia, is one of the largest coalfired power plants in Asia. The contract for the design, manufacture, supply, erection and commissioning of the coal handling system was awarded to TKF.
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Experimental Device. The "gascontaining coal thermalfluidsolid coupling threeaxis servo seepage system" developed by Chongqing University (Fig. 2) was used to study the effect of variable confining pressure unloading rate on coal deformation and permeability characteristics during the alternate loading and unloading device has a maximum axial force of 1000 kN, a ...
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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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Discussion on bulk carrier loading and unloading operations and freight safety for the owner's and master's responsibilities and ... Hu SP, Jin YX, et al. Performance simulation of the transportation process risk of bauxite carriers based on the Markov Chain and Cloud model. J Mar Sci Eng 2019; 7(4): 116. Crossref. Google Scholar. 7. ...
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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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A new energydissipation method to identify crack initiation and propagation thresholds is introduced. Conventional and cyclic loadingunloading triaxial compression tests and acoustic emission experiments were performed for coal specimens from a 980m deep mine with different confining pressures of 10, 15, 20, 25, 30, and 35 MPa. Stressstrain relations, acoustic emission patterns, and ...
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In this paper, the alternate loading and unloading by stages tests of raw coal samples were carried out by using the "Triaxial seepage test device of thermal fluid solid of coal and rock", the conclusions are as follows: The axial strain change rate ε 1 ′, the radial strain change rate ε 3 ′ and the permeability change rate k′ under unit stress state are used to represent the ...
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Compared with the axial loading rate, the hoop unloading rate is the main reason for the change of the rock failure mode . Ma et al. found that the rapid unloading intensified the damage of coal samples before and after rupture, resulting in a sharp increase in the damage curve. Therefore, in actual production, the excavation speed of coal and ...
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Coalburst is a violent dynamic failure of coal during underground mining. It is of significance to study failure pattern as well as energy evolution and transition during coalbursts and how they are influenced by preconfinement. This paper presents unloadinginduced coalburst simulations using the distinct element method via a combined staticdynamic loadingunloading strategy.
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During the cyclic loading and unloading process, assuming that there was no energy exchange between the machine and the external environment, the test equipment transferred energy to the sample through mechanical work, part of which was converted into elastic energy stored inside the coal body, and could be completely released during unloading ...
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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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