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 ...
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 ...
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
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.
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 ...
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.
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 ...
Cyclic Loading and Unloading Process. Based on the results of AE filtering experimental results, the loading process for the ultrasonic test experiments carried out in this study is as follows: measure the ultrasonic wave parameters before the process of loading, load up to kN and maintain the force for 34 minutes; load up to kN and maintain the force for 34 minutes; unload up ...
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 ...
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 %.
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.
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 ...
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 ...
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.
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.
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.
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 ...
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.
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 ...
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.
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 ...
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.
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 ...
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.
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 ...
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
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. ...
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 ...
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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