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The rock mass is change during mining, according to their evolutionary characteristics, the model of movement and destruction of rock mass was built up. Then the authors researched on the correlation between attenuation index of mass subsidence factor and the breaking number of unit length rock according to the law of the rock mass rupture. After that, we gained the functional relationship between the fracture length of rock mass and the mining height by regression fitting using of underground measurement data of field observation, at the while, we derived to confirm the relationship formula of subsidence factor with the mining height and influence coefficient of lithology. The results show that the subsidence factor decreases with the increase of the mining height, which approximately presents the negative logarithmic function relationship between them, and under different lithology, subsidence factor has different value; the harder the mass, the smaller the value, vice versa. [ABSTRACT FROM AUTHOR]

In order to study the formation mechanism and evolution laws of gas flow channel in mining coal and rock, using relevant theories of fracture mechanics and rock mechanics with combinations of mining coal and rock's crack development characteristics, the gas flow channels in mining coal and rock ahead of working face were divided into isolated channel area, tensile fracture failure area, shear failure area,and failure area after abutment pressure peak. And according to the developmental process of crack in mining coal and rock and formation mechanism of gas channel in different areas, it's concluded that the first three areas belong to mesoscopic channels, and the fourth area belong to macroscopic channels. According to the relevant theories of material mechanics and deformation and mechanics characteristics of coal roof, crack developmental process and channel conduction property during mining process, roof macroscopic gas channels were divided into three areas from above to below; gas turbulent channel area, gas transition flow channel area and gas seepage channel area, and combined with simulation in laboratory, the development process of gas channel in overlying coal (rock) seams were analysed, which experienced the process of decompression, instability, crack initiation, mutation splitting, anastomosis contraction, accelerated closed, channel preservation, accelerated closed again and compaction closed completely. [ABSTRACT FROM AUTHOR]

Aiming at the problems of buried tube nitrogen injection that the nitrogen injection spot with intervals in the space causes the failure of continuous nitrogen distribution in goaf, leading to poor inert effect. In addition, the unrecycling of the nitrogen injection pipe causes great resources waste. Based on the principle that the shear capacity of the mining nitrogen injection pipe is superior to its tensile strength, new fire nitrogen injection process (rotating traction and non-interval) was designed, fundamentally solving major defects of buried pipe nitrogen injection, which can realize the synchronous movement between nitrogen injection point and the workface. According to the relevant principles of planar problems in elastic mechanics, the calculation method about dynamic parameter of non-interval nitrogen injection process for fire control was put forward. By using a geotechnical engineering numerical simulation software, the stress distribution of the nitrogen injection pipe in the goaf of Yanzishan Mine was simulated, and the traction power was computed based on it. [ABSTRACT FROM AUTHOR]

For studying the regularity of strata behavior in mining face in thin bedrock with thick surface soil, the stability of structure of main roof were analyzed based on Lijiahao Coal Mine, and numerical simulation software UDEC was used to analyze the regularity of strata behavior in mining face under different ratio of rock and loadings, combined with field measurement of mining coal, block degree of rock i and ratio of rock and loadings were separately put forward to judge the stability of structure of main roof. It was considered analysis that the three-hinge arch structures formed after main roof breaking and the monoclinic structure formed after contacting waste rock of main roof will occur sliding instability when the block degree of rock i is more than 0.40 and less than 1.57; overburden also takes place sliding instability phenomenon easily when first weighting or periodic weighting of the main roof comes; key strata represents sliding instability in thin bedrock with thick surface soil, while it is not large of the ground pressure of regional in front of coal wall when the roof weighting comes; during the roof weighting coming, the regularity of strata behavior in thin bedrock with thick surface soil is that main roof cuts and splits along the coal wall, and emerges roof steps, the dynamic load action on face shield comes obviously. [ABSTRACT FROM AUTHOR]

A sulfate-reducing bacteria(SRB) strain, named GY-2,was isolated from groundwater in a 705 m deep aquifer at a coal mine in Huaibei Plain for mechanism analysis on the abnormally low sulfate concentration in the coal measure strata groundwater, and was identified as Desulfotomaculum guttoideum by Phylogenetic analysis based on 16S rRNA genesequence. The strain GY-2 is found to be anaerobes, mesophilic and suitable in neutral or alkalescent, low or medium water mineralization environment, and Fe2+ significantly promote the SRB strain growth. It is explained with the relationship between sulfate-reduction, redox potential and chemical types of groundwater, why the ratios of Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. change from high to low and to high again as the depths of the water-bearing strata increase continuously. [ABSTRACT FROM AUTHOR]