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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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 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 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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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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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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As the coal body has a hysteresis effect during the unloading process, it cannot be unloaded to 0 when unloading, and the minimum unloading level was set for the four kinds of samples; that is, after unloading to 2% σ c, the loading was performed until the sample was destabilized.
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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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In the course of the experiment, the stress, strain and permeability of raw coal under loading and unloading conditions were recorded, and the specific experimental process was as follows: (1) First, the raw coal sample is scanned by CT apparatus, and then the sample coated with silica gel is installed in the pressure chamber. (2)
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Pollutants for Coal Storage, Loading, and Unloading in Ports A Case Study of Wharf in Tianjin Analysis of Dusting Links in Coal Storage, Loading, and Unloading The eld survey and literature review indicate main pollutants come from dust generated by agitation, dropping, or strong wind in the process of coal loading and unloading,
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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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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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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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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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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 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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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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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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Mining under the sea is a challenging task in China. Affected by blasting, tunneling, and other engineering disturbance, surrounding rock is often in a state of cyclic loading and unloading stress. In this study, in order to investigate the effect of cyclic loading and unloading on the deformation and damage characteristics of sandstone underneath the Bohai Sea, the GCTS test machine is used ...
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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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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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Load restraint: Load restraint includes lashing/unlashing, tie down, twistlock locking/unlocking for the purposes of ensuring a load is secured to the truck to meet the performance standards in the load restraint guide or unsecured in preparation for removal. Safe zone: is an area free of interaction between equipment/machinery and people. The safe
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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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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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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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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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A semicontinuous process system consisting of a singlebucket excavator, truck, crushing station, and belt conveyor is the main coal mining process system of a largescale hard coal openpit mine. Through analyzing the coal mining production process, the key issues of coal mining truck flow optimization are obtained. Statistical method of using triangular fuzzy numbers analyzes the key time ...
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The cumulative AE energy and energy dissipation density are linearly correlated during the cyclic loadingunloading process, which indicates a possibility in estimating the damage evolution and the dynamic failure risk of coal via cumulative AE energy, under the cyclic loadingunloading condition.
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A material supplier from Belgium would like to produce limestone powder for his custome...
India is rich in various mineral resources and it is an important mineral processing market
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