scholarly journals Specific Energy of Hard Coal Under Load

2015 ◽  
Vol 37 (1) ◽  
pp. 9-16 ◽  
Author(s):  
Anna Bogusz ◽  
Mirosława Bukowska
Keyword(s):  
Kinetic Energy ◽  
Total Energy ◽  
Uniaxial Compression ◽  
Specific Energy ◽  
Compression Strength ◽  
Longitudinal Strain ◽  
Full Range ◽  
Dissipated Energy ◽  
Uniaxial Compression Strength ◽  
Recoverable Energy

Abstract The article presents results of experimental tests of energy parameters of hard coals under loading, collected from research sites located within five main geologic structures of Upper Silesian Coal Basin (GZW) - Main Trough, Main Anticline, Bytom Trough, Rybnik Trough and Chwałowice Trough. Coals from12 mines were analysed, starting with seams of group 200, through groups 400, 500, 600 and, finally, seams of group 700. Coal of each of the groups of seams underwent uniaxial compression stress of the energy parameters, in a servo-controlled testing machine MTS-810NEW, for the full range of strain of the tested coal samples. Based on the tests the dependence of different types of specific energy of longitudinal strain of coals on the value of uniaxial compression strength was determined. The dependence of the value of dissipated energy and kinetic energy of coals on the uniaxial compression strength was described with a linear function, both for coals which due to their age belong to various bed sand for various lithotypes of coal. An increase in the value of dissipated energy and in kinetic energy was observed, which was correlated with an increase in uniaxial compression strength of coal. The share of dissipated energy is dominant in the total energy of strain. Share of recoverable energy in the total energy of strain is small, independent of the compression strength of coals and is at most a few per cent high. In coals of low strength and dominant share of dissipated energy, share of recoverable energy is the biggest among the tested coals. It was shown that following an increase in compression strength the share of recoverable energy decreases, while the share of dissipated energy in the total energy increases. Further studies of specific energy of longitudinal strain of rocks in the full-range strain will be the next step inperfecting methodology of research into natural rock burst susceptibility of Carboniferous rock mass and changes in the susceptibility resulting from mining activity.

scholarly journals Freeze-Thaw Cycle Effect on Sputtering Rate of Water-Saturated Yellow Sandstone under Impact Loading

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Yunbing Hu ◽  
Tianzhu Duan ◽  
Penghui Xian ◽  
Liang Chen
Keyword(s):  
Kinetic Energy ◽  
Specific Energy ◽  
Impact Loading ◽  
Freezing Temperature ◽  
Dissipated Energy ◽  
Particle Sizes ◽  
Loading Test ◽  
Freeze Thaw ◽  
Water Saturated ◽  
The Impact

In order to explore the impact of freeze-thaw temperature on the sputtering rate of water-saturated yellow sandstone under impact loading, in this paper, the Hopkinson pressure bar is used to conduct impact loading test on the water-saturated yellow sandstone at the same strain rate (74.22 s−1) under five different freeze-thaw temperatures. After impact loading, the yellow sandstone fragments are graded and screened by using the sizing screen, and the mass of fragments with different particle sizes after screening is counted. By transforming the fragments into spheres with the corresponding particle sizes, and combining the dissipated energy, the surface specific energy of yellow sandstone with different freeze-thaw temperatures is calculated. Finally, the sputtering rate of the fragments is obtained by using the relationship of total work, dissipated energy, and kinetic energy. The main conclusions are as follows: The freeze-thaw temperature has a significant effect on the fracture degree of yellow sandstone. The lower the freeze-thaw temperature is, the higher the fracture degree of yellow sandstone is, and the smaller the particle size distribution of fragments is. The fractal dimension of yellow sandstone increases with the decrease of freeze-thaw temperature, indicating that the damage of yellow sandstone is more serious. The dissipative energy of yellow sandstone increases with the decrease of freezing temperature, while the kinetic energy increases gradually when the freeze-thaw temperature is −30°C to −15°C and decreases gradually when the freeze-thaw temperature is −15°C to −5°C. The surface area and surface specific energy of yellow sandstone fragments both increase with the increase of freeze-thaw temperature. And the sputtering rate of yellow sandstone fragments increases gradually at freezing temperature from −30°C to −15°C and decreases gradually at −15°C to −5°C. Therefore, from the perspective of dynamic destruction process, the sputtering of yellow sandstone fragments at freezing temperatures of −15°C, −20°C, and −30°C is more intense than that at −5°C and −10°C. The results can provide some guidance for production in winter and winter regions.

Influence of the Dry Bulk Density on the Properties of Ceramic Paver Body

2014 ◽  
Vol 805 ◽  
pp. 536-540
Author(s):  
Veronica Scarpini Candido ◽  
Regina Maria Pinheiro ◽  
Sergio Neves Monteiro ◽  
Carlos Maurício Fontes Vieira
Keyword(s):  
Water Absorption ◽  
Bulk Density ◽  
Uniaxial Compression ◽  
Compression Strength ◽  
Technological Parameter ◽  
Uniaxial Compression Strength

This work has as its objective to evaluate the influence of the dry bulk density in precursor body formulations developed to fabricate ceramic paver. Cylindrical specimens were uniaxial press-molded into two dry bulk density ranges, 1.99-2.05 g/cm3and 2.18-2.23 g/cm3, from three formulations elaborated with clays, argillite and grog and then fired at 850 and 950oC. The evaluated properties were: water absorption and uniaxial compression strength. The results indicated that the packing during the forming stage is an important technological parameter that significantly influences the evaluated properties.

scholarly journals Mechanical Behavior of Frozen Porous Sandstone under Uniaxial Compression

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-6
Author(s):  
Hong-Ying Wang ◽  
Qiang Zhang
Keyword(s):  
Tensile Strength ◽  
Longitudinal Wave ◽  
Uniaxial Compression ◽  
Wave Velocity ◽  
Compression Strength ◽  
Peak Strain ◽  
Secant Modulus ◽  
Longitudinal Wave Velocity ◽  
Uniaxial Compression Strength ◽  
Porous Sandstone

The influence of low temperature on longitudinal wave velocity, uniaxial compression strength, tensile strength, peak strain, secant modulus, and acoustic emission characteristics of yellow sandstones was studied. The results show that the secant modulus increases with decreasing temperature when the axial strain is less than 0.6%, and a contrary influence performs for the subsequent stage due to the fracture of the pore ice. With the decrease in temperature, the uniaxial compression strength first increases and then remains at a relatively constant value of 34.44 MPa at about -40°C while the temperature ranges from -40°C to -70°C. The tensile strength shows an approximate linear increment as the temperature. The peak strain gradually increases with temperature in a three-stage piecewise linear form, and the increasing rate gradually decreases with the decreasing temperature. The phase transformation from liquid water at a temperature of 20°C to solid ice at a temperature of -3°C significantly increases the longitudinal wave velocity from 1.55 km/s to 3.36 km/s. When the temperature is lower than -10°C, the longitudinal wave velocity approximately increases linearly at a rate of 2.67 × 10 − 3   km / s · ° C − 1 with decreasing temperature.

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