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Currently, mine safety is the focal point in mining activity. As a new and advanced approach for geophysical prospecting, the ground penetrating radar (GPR) is used in the mine disaster detection. Aiming to solve the restriction of low resolution and limited depth of the GPR in the deep coal seam detection, the computed tomography (CT) technology is employed for deep disaster detection in this paper. A large number of coal seam digital simulation model, including different internal diseases, are established, and the simulation data are processed by using the Least Square QR-factorization (LSQR) inversion algorithm, which has the good performance in saving computational time and memory space. Additionally, the influences of iteration precision and grid size on the effect of inversion are analyzed. The inversion results show good agreements with simulation model feature configurations, and the diseases objects can be detected.

The ground cracks caused by mine activities lead to soil destruction in sandy area. Most of the previous literatures focus on the soil properties change before and after the large area subsidence, and the research of the ground crack impact on soil are inadequate. This paper takes the soil around the static cracks as the research object, analyzes the impact law of the soil total nitrogen by using the comparative analysis method. The impact law and impact range of the soil total nitrogen by ground crack, and the impact mechanism of the soil porosity and soil particle size, are analyzed. The result show that: within 200cm away from static cracks, the soil total nitrogen content is decreases in the close distance, increases in the middle, and keeps gentle change in the long distance; The effect boundary of the total nitrogen by static cracks is about 100cm, providing information for further study on the soil quality influenced by coal mining in the sandy area.

Removed at authors request

In this paper, α-Si3N4 was mixed with Y2O3 and MgO by ball milling. Spray granulation was adopted to fabricate spherical powder. The influence of the sintering temperature and the holding time on the thermal conductivity of the powder was studied. The results show that α-Si3N4 raw powder was transformed into β-phase after sintering. Spherical powder, of which the diameter is about 20 μm, was fabricated. Some compounds such as YMgSi2O5N, Y4Si2N2O7 and Y2Si3N4O3 were generated in the samples. The thermal conductivity of the pressed powder first increased then decreased with the sintering temperature rising, showing a maximum at 1800°C. Also the thermal conductivity first increased then decreased as the holding time getting longer, showing a maximum at a sintering time of 2 hours.