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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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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Unloading PRB coal cars with a Dravo rotary dumper
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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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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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Coal failure is often the precursor of dynamic disaster. The energy evolution behaviour at different stress values was analysed under the gradation of equal amplitude cyclic loading/unloading. Based on the energy dissipation behaviour, the energy evolution model of the coal specimen was established. The multiparameter energy behaviour predicting model was proposed.
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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 sample. M ...
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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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In this study, coal fly ash was functionalized, using a simple onestep process (loading with Al3+ and sulfonation), to yield a solid acid catalyst (S/AlCFA) with strong acid sites. The catalyst was then used to produce furfural from xylose in a biphasic system (H2O(NaCl)/tetrahydrofuran). The furfural yield reached 82% at 180 °C60 min with catalyst/xylose ratio of : (w/w). With the ...
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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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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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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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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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Compared with the loading approaches mentioned above, the cyclic loadingunloading testament is an effective approach in revealing the mechanical response of coal and rock under repeated disturbance of excavation, 47, 50, 51 through parameters, such as peak strength, elastic modulus, and energy dissipation features. 33, 47, 48, 52 Though many ...
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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 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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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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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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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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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
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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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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 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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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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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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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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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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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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To study the anisotropic mechanical properties and energy evolution of layered rock masses under the action of cyclic loading, uniaxial graded cyclic loading and unloading tests under different upper and lower stress limits were carried out on samples with different bedding angles (0°, °, 45°, °, and 90°) to explore the deformation and mechanical response characteristics of bedded ...
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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 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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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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