Hunan Coal Science Research Institute

Abstract Coal elasticity and gas expansion are important factors for coal and gas outburst. During the outburst process, the elastic strain energy of coal is mainly released from the stress region, and the gas expansion energy near the working face is larger, and it is not a continuous release process. To reveal the mechanical characteristics and energy evolution of outburst coal seam, uniaxial and triaxial compression tests were carried out on outburst coal seam samples under different loading methods. The experimental results show that the elastic characteristics become more obvious with the increase of loading rate, the peak strain increases, the elastic modulus is linearly related with the loading rate，and the overall degree of fragmentation increases with the increase of loading rate, which is consistent with the severity of macroscopic coal failure. The failure mode of coal under uniaxial compression conditions is often manifest as brittle failure. The strength characteristics of coal under different loading rates comply with the Mohr‐Coulomb criterion, and the peak strength is linearly related to the failure time and loading rate. With the increasing confining pressure causes the failure of coal samples to transition from ductile to brittle, and the failure mode develops from local shear to overall splitting. The elastic energy evolution curve is consistent with its stress‐strain curve. With the increase of confining pressure, the limiting elastic energy and peak total energy increase in a quasi‐linear manner. The accumulated limit elastic energy plays an important role in the failure of coal samples, and the macroscopic manifestation thereof is that the coal samples fail more severely under high confining pressure conditions than under low confining pressure conditions. The research results are of great significance for the comprehensive prevention and control of coal and gas outburst.

Aluminosilicate phosphors have been successfully applied in laser technology and fluorescent lamps due to their high luminescence properties and excellent chemical stability. Consequently, research on novel aluminosilicate phosphors has a good application prospect. Rare earth (RE) ions doped SrAl2Si2O8 phosphors were prepared by solid-phase method. Excited at 350 nm, the phosphor doped with Dy3+ ions emits a blue light peaking at 482 nm and an orange light peaking at 575 nm, respectively, and its optimum doping concentration is 0.8 at.%. At the NUV excitation of 377 nm, the phosphor doped with Tb3+ ions shows emission peaks at 489 nm, 544 nm, 585 nm and 623 nm, and the luminescence intensity is the strongest when the content of Tb3+ is 9 at.%. The concentration quenching mechanism of Dy3+ and Tb3+ RE ions is the electric dipole–dipole interaction. For SrAl2Si2O8:Tb3+, Sm3+ phosphors, the energy transfer efficiency is 85.4%, and the mechanism is electric dipole–quadrupole interaction. For SrAl2Si2O8:Dy3+ and SrAl2Si2O8:Tb3+, Sm3+ phosphors, the best CIE coordinates are (0.275, 0.308), (0.316, 0.386). The consequences display that RE ions doped single matrix SrAl2Si2O8 phosphors can achieve effective white light emission and have high application value in white LEDs.

This research intends to obtain the pressure relief angle of protective scope through research and study of the protective scope and effects after mining of coal seam No. 2 as the protective seam of coal seam No. 5 in mining area No. 23 of Jinzhushan Mining Co., Ltd. CBM flow attenuation coefficients of taps within protective area are reduced from 0.016 and 0.015 d-1 before mining to 0.008 and 0.011 d-1; and average CBM extraction amount in seven days is raised by two to three times. This research provides scientific basis for mining of protective seams for the mine.