Journal of China Coal Society, the 1st in the field of mining engineering, promotes the development of coal theory and practice, as well as academic exchanges at home and abroad to accelerate the transformation from scientific research to real productive forces. It is supervised by China Association for Science and Technology and sponsored by China Coal Society. Launched in 1964, it aims at providing key topics of coal scientific research and mining development. Its scope covers coal geology, geochemistry, geophysics, mineralogy and coal seam formation and evolution; petrophysics of coal; organic matter-rich shales, including mineralogy, formation, transport and storage of gases in coal and shales; unconventional energy systems (e.g. oil shales, shale gas, and other carbon-based fuels); ore deposits of materials and rare metals in coal and coal-bearing strata; and groundwater management.
The journal is included in CA, JST, EI, CSCD.
Editor-in-Chief Liu Feng
Associate Editor Fan Baoying, Xu Shengyang, Zhu Shuangcheng
In order to reveal the dynamic mechanism of support and surrounding rock in a fully mechanized mining face, the mining process was divided into several roof active cycles and every roof active cycle was divided into several mining cycles. The double period dynamic mechanism of support and surrounding rock was put forward, based on the bond-beam structure mechanical model, elastic base beam theory and Newton’s second law. During the roof active cycle, the results showed that the state of the block A in the bond-beam structure model touching the gangue was the key node to judge the variation trend of the final resistance. The resistance increased before the key block A touching the gangue, and reduced after touching. In the mining cycle, the study showed that the structure of bond-beam was mainly sustained by bases which had different elastic moduli and composed of coal wall, hydraulic support and goaf. According to the different increasing characteristics of the resistance, the interaction process of support and surrounding rock in mining cycle was divided into a given load stage and a given deformation stage, and the resistance function of dynamic increasing was put forward. The increasing curve in the given load stage followed an exponential function, and the curve in the given deformation stage followed a logarithmic function. The fitting results of the data measured in workface with the Sihe Mine and Xinyuan Mine, indicated that the field measurement was consistent with the theoretical analysis. The above research would provide a theoretical basis for roof disaster prediction and strata control.
In order to investigate the characteristics of the production of biogas from lignite with acid-alkali pretreatment, the authors carried out the fermentation experiments of hydrogen and methane production by using cultured bacteria from coal seam water in Guhanshan coal mine, as well as acid and alkali pretreatment of lignite in Yining Mine, Xinjiang. The authors measured the gas production, gas components, activity of hydrogenase, COD concentration, and tested XRD and FTIR for coals after gas production. The results show that ① the hydrogen production of coal with alkali pretreatment is the highest with the total gas production of 20.25 mL/g, that of coal with acid pretreatment is 17.05 mL/g, and the lowest hydrogen production is found in raw coal as 14.4 mL/g; ② the determination of HPE is basically corresponding to it, and the hydrogenase activity of hydrogen production from coal with alkali pretreatment is 4.35 mL/(mg·min); ③ the methane production of coal from acid pretreatment is the best, and the total gas production is 23.35 mL/g, while the effects of raw coal and the coal with alkali pretreatment are similar; ④ the concentration of COD in the combined production shows a decrease; ⑤ the organic matter degradation rate of the pretreated coal sample is higher, and the macromolecular structure is more easily degraded. The results show the fermentative biogas characteristics of pretreated coal, and it proves that the combined production of H
2-CH
4 is beneficial to the utilization of coal, which obviously improves the energy conversion rate.
The mathematical model of temperature field under unsteady state of surrounding rock was established based on the energy conservation law and Fourier’s law according to the heat dissipation characteristics of temperature field of roadway surrounding rock. The calculation program was worked out by using finite volume calculation method, and the temperature field of surrounding rock of roadway was calculated. Similar experimental platform for temperature field of roadway surrounding rock was established, and the simulation results of the finite volume method were verified by the experimental results. It was found that the calculation results of finite volume method coincided with that of similar simulation experiments. The variation trend of space-time curves of temperature field obtained by both methods is consistent. It shows that it is correct and scientific to apply the finite volume method to establish the mathematical model and the calculation program. Based on the simulation results and experimental results, the factors affecting the unsteady state change of the temperature field of the surrounding rock under constant air flow temperature were analyzed, and the variation law of unsteady state temperature field of roadway surrounding rock was obtained. The unsteady state process of temperature field of roadway surrounding rock was analyzed and the heat dissipation of surrounding rock was calculated based on the engineering background.
Based on the calculation theory of box-counting dimension, a calculation method to calculate the fractal dimension of blast-induced cracks is proposed, and the relationship between fractal dimension and damage degree by blasting is established. A box-counting dimension algorithm based on digital image is compiled using Matlab software. The fractal character of blast-induced cracks under both ordinary charge blasting and slit charge blasting is analyzed using the boxing-counting dimension algorithm, and the damage degree of different regions around borehole is determined. The results show that, in ordinary charge blasting, the damage degree induced by blasting reduces with crack propagation, but almost the same in the same regions away from the borehole. In slit charge blasting, the damage degree of blast media presents a significant regional and orientated character. In region I, compared with that induced by the ordinary charge blasting, the damage degree induced by blasting along the slit direction slightly decreases, which reduces significantly in the non-slit direction. In region II, the damage degree induced by blasting along the slit direction increases compared with that in the same region in ordinary charge blasting, while the damage degree decreases in the non-slit direction. In region III, the damage degree along the slit direction increases significantly, while it decreases in the non-slit direction. The calculation of damage degree induced by blasting based on fractal dimension can be used to quantitatively evaluate the spatial distribution characteristics of blast-induced cracks, so as to explore a new way to study the evaluation law of damage degree induced by rock blasting.
By establishing thin plate mechanical model of main roof with elastic foundation boundary and using the finite difference theory, the paper studies the effect of elastic foundation coefficient
k, main roof thickness
h, main-roof Young modulus
E, the hanging roof length
a1, the ratio
k/
E and
k/
h to the main-roof primary bending moment and periodic fracture regularity. It is concluded that with the increase in the
E or
h, the absolute maximum primary moment
Md of short side and
Mc of long side, and the maximum primary moment
Md of suspended roof’s rear boundary all increase; while with the increase in the
k, the primary moments
Mc,
Mb and
Md all decrease, and the decrease amplitude of the
Md is the biggest. According to the fracture criterion of primary moment, the value of
E,
h or
a1 is big, or the value of
k is small. The upper surface of the short side ahead of the coal wall first fractures, whereas the long side ahead of the coal wall first fractures; if the ratio
k/
E or
k/
h3 is unchanged, the primary moments
Mc,
Mb and
Md are unchanged and the initial fracture position of main roof is unchanged. The periodical fracture types of main roof with elastic foundation boundary are: ① long side upper surface → short side upper surface → lower surface of suspended roof’s rear boundary; ② short side upper surface → long side upper surface → lower surface of suspended roof’s rear boundary.
The abundant coalbed methane exploration in the southeast margin of Junggar Basin has not made a great breakthrough for its complicated geological structure and reservoir formation mechanism. Therefore, its accumulation mechanism and main controlling factors become the most critical constraint issues for CBM exploration. On the basis of the fine dissection about geological conditions of the coalbed methane here, the characteristics of coalbed methane accumulation and the reservoir formation mechanism are revealed. The authors found that the coal seams controlled by complicated geological structure, with east-west fault and anticline, are mainly developed in the Tianshan piedmont fault fold belt. And the coal seams and sandstone were superposed. Also, the high porosity of coal has good pore connectivity. As a whole, the gas content is generally high in the west and low in the east. Therefore, this paper established a mixed gas source enrichment model of the coalbed methane accumulation pattern of sealing property by structure and hydrodynamic water in the steeply inclined coal seam. And it is concluded that the sealing zone with relatively high pressure is the favorable area for coalbed methane accumulation. So the relatively high point of the structure and the transitional zone between surface water and groundwater should be optimized in the exploration of coalbed methane. Therefore, the authors suggest to carry out stereoscopic exploration in the Fukang-Mount Huangshan favorable target area.
