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Shan R.L.,China University of Mining and Technology | Zhang C.J.,China University of Mining and Technology | Zhang C.J.,Datong Coal Mine Group | Zhao X.,China University of Mining and Technology | Wu S.J.,China University of Mining and Technology
Applied Mechanics and Materials | Year: 2014

With the development of the economy, and investment structure is more complex, more investment direction is more diversified, capital investment efficiency is affected by more factors. Deep analysis and evaluation of the efficiency of investment and the objective and fair to find the factors that are critical for any investment or personal legal person. Based on the research of domestic and foreign scholars, this paper analyzed the influencing factors of coal mine construction investment efficiency from the theoretical level. © (2014) Trans Tech Publications, Switzerland. Source


Lin C.,Tsinghua University | Deng J.,Tsinghua University | Liu Y.,Tsinghua University | Yang Q.,Tsinghua University | Duan H.,Datong Coal Mine Group
Journal of Petroleum Science and Engineering | Year: 2016

Hydraulic fracture geometry is of paramount importance to enhance fracture effect in colliery hard roof control. Near wellbore complexity often resulted in low lateral dimension of induced fracture hence the fracking effect of the treatment. In the past, near wellbore fracture geometry is mainly believed to be controlled by the interaction between hydraulic fracture initiation and natural fracture infiltration/opening. Recently, lab experiments have proved that transverse notch plays a role in lowering breakdown pressure and also in reducing near wellbore complexity. Besides, colliery hard roofs are often over-pressured, therefore, with the increase of pore pressure, the influence caused by stress difference is weakened, and the role of notch becomes significant. In this paper, a series of lab experiments are conducted to gain in-depth understanding of the role transverse notch plays on near wellbore geometry and fracture reorientation. Hydraulic fracture process is physically simulated by injecting water (green dyed) at some certain rate into a pre-installed tube in a block (300×300×300 mm) under tectonic stress condition. Different notch parameters and fracturing regimes are used to make comparison. The notch changes the local stress and strain field in the blocks and affects the way blocks deform and fail. Post-mortem analysis and photo image of the block clearly show: (i) the length and angle of initial notch play a role in determining: near wellbore geometry and fracture reorientation; (ii) near wellbore fracture complexity may be reduced by making a longer initial notch and picking an appropriate notch angle; (iii) better understanding can be achieved by conducting further researches under normal stress condition and taking more factors into consideration. © 2015 Elsevier B.V. Source


Xie Q.,China University of Mining and Technology | Yao X.,China University of Mining and Technology | Yang C.,China University of Mining and Technology | Jiang Y.,China University of Mining and Technology | And 2 more authors.
Meitan Xuebao/Journal of the China Coal Society | Year: 2015

A series of granular activated carbons (GACs) were prepared by briquetting method from five typical Chinese coals of different coalification degrees (Shengli lignite, three subbituminous coals including Lingwu coal, Shenmu coal and Datong coal, and Taixi anthracite). The effects of coalification degree on the pore structure development of activated carbon were investigated with the aids of the mineral constitution and content of the coal and the crystalline parameters of the char. The results show that: (1) layer thickness (Lc) and graphitization degree (G) increase with the increase of the coalification degree (Cdaf), which leads to larger BET specific surface area (SBET) and smaller average diameter (da) of the activated carbon; (2) Mineral matters in the coal also affect the pore structure of activated carbon significantly: high mineral content means less organic carbons available for pores shaping while Fe-and Ca-containing minerals in the char catalyze the gasification reaction, promoting pore structure development. The pore structure of activated carbon prepared by briquetting method is highly affected by coalification degree because chars with different crystalline sizes and mineral constitutions are formed after carbonization. ©, 2015, China Coal Society. All right reserved. Source


Jin W.,University of Sichuan | Gao M.,University of Sichuan | Yu B.,Datong Coal Mine Group | Zhang R.,University of Sichuan | And 2 more authors.
Environmental Earth Sciences | Year: 2015

Roof-coal recovery rate and the performance of gas extraction are essentially controlled by the fractures within coal-rock mass. Thus, it is important to generate the accurate fracture network ahead of mining face. In this study, ten boreholes located differently from the 8212 working face of Tashan Mine in Datong coal mining group, China, were drilled. With the help of borehole video instruments, the location, orientation of each fracture and the fracture number of different intersection type on each borehole wall were mapped with the advancing of mining face. These data were analyzed using the Matlab Toolbox RJNS3D and Dips to determine structural homogeneity zone, to find the number of fracture sets that exist in the coal-rock mass, volume density frequency for each set and the probability distributions of orientation, fracture size in 3-D. Sampling biases associated with orientation, spacing were corrected during the process. The constructed fracture networks were validated by comparing the observed mean spacing along normal vector of mean orientation for each set and the predict value on similar scanlines. © 2015, Springer-Verlag Berlin Heidelberg. Source


Yu B.,Datong Coal Mine Group | Zhang R.,University of Sichuan | Gao M.-Z.,University of Sichuan | Li G.,University of Sichuan | And 2 more authors.
Thermal Science | Year: 2015

Numerical study of mining-induced stress evolution of coal during the top coal caving process under different coal seam thicknesses is carried out, and the numerical prediction agrees well with the field test data. Main characters on stress distribution and dangerous area are elucidated. For the same coal quality, coal layers under 7 m thick fail earlier than thicker coal layers; correspondingly, the internal fracture networks of thin layers are more easily developed. During the mining of a coal layer less than 7 m thick, stress monitoring of the "dangerous area" in the middle of the top coal should be emphasized, whereas during the mining of coal layers less than 11 m thick, stress monitoring of the "dangerous area" at the bottom of the top coal should be highlighted. The research is to optimize caving technique and extraction process. Source

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