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Chen G.,China University of Mining and Technology | Chen G.,Huaibei Mining Group Company
Energy Education Science and Technology Part A: Energy Science and Research

By describing the design and construction of directional drilling long borehole and the effect of the gas drainage, the paper indicated that the process is stable, low cost and convenient to control, by which the gas will be extracted after been relieved by the protective layer. Compared with the other processes being used on the ground, the advantages are more prominent, the process is valuable in promotion and application. © Sila Science. All Rights Reserved. Source

Wang J.-M.,North China Institute of Science and Technology | Yu D.-H.,Huaibei Mining Group Company
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering

Hazards due to stratum separation are a type of roof water hazards that unexpectedly happen under the conditions without any water reservoir. However, the hazard origins have not been understood or explained, resulting in great difficulties in control of water hazards in coal mines. To solve the problem, Haizi Coal Mine is taken as a case study. The hydrogeological, geotechnical and mining conditions are analyzed. The roof stratum failure and displacement are analogized physically and simulated numerically. A new type of water hazards is found finally, and a new theory for the mine hazards, i.e. water hazards caused by burst of water cells formed by overburden stratum separation, is put forward. The drilling and borehole camera scanning have verified the above theory. According to the theory, the dynamic draining measures are proposed and used successfully in the control of water hazards. The research achievements are applied to other working faces with the similar hydrogeological conditions for coal mining safety. The investigation on the hazards by simulations not only theoretically fills the gap of water hazard classification for coal mines, but also finds a way for the control of water hazards in coal mines. Source

Chen G.,Huaibei Mining Group Company
Meitan Xuebao/Journal of the China Coal Society

According to the special geological conditions of the ultra soft, combustible and special thick seam in Zhuxianzhuang Mine of Huaibei mining area, a rational allocation was conducted for the coal mining face equipment. The tip to face control of coal wall was realized by the top coal control and water injections to the shallow borehole of the coal mining wall. With the lab simulation and the mine site technique experiment, the top coal caving technique with the "two coal mining passing and one top coal caving operation" and the multi sequence top coal caving was set up. The coal spontaneous combustion in the goaf during the face mining period could be effectively prevented and controlled with the buried tube grouting, the gel grouting at the top and bottom corners of the coal mining face, and other comprehensive fire prevention and control measures. With the effective mine site management, the fully mechanized top coal caving mining under the ultra soft, combustible and special thick seam was successfully applied to 8 coal mining faces in Zhuxianzhuang Mine with a coal mining rate over 87%. Source

Jiang J.,Shandong University of Science and Technology | Zhang P.,Shandong University of Science and Technology | Nie L.,Huaibei Mining Group Company | Li H.,Shandong University of Science and Technology | And 2 more authors.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering

An elastic model of thin plate with three edges fixed and one simply supported was established as the mechanical model of high and thick strata of hard magmatic rock at working front 10416 in Yangliu coal mine, A flexural function and an analytic expression of stresses for the hard and thick strata were derived with Rayleigh-Ritz method. A formula of fracture span was obtained; and then a method of calculating the length of drawing pace of fracturing according to fracture morphology of overburden was proposed. The analysis of monitored results of microseism, supporting pressures and surface subsidence revealed the fracture process and the dynamic response of high and thick strata of hard rocks. The point of maximum deflection prior to fracturing of strata is at the location of x=a/2 and y=13b/(10π), where a is suspension length along the strike of hard-thick strata; b is suspension length along the tendency of hard-thick strata. Fracture first happened along the dip clamper edge if a<1.049b, along the strike clamper edge otherwise. The initial form of fracturing is "O-X" shaped, which is symmetrically along the strike but asymmetrically along the tend. Microseismicity intensified during the process of fracturing and movement of strata leading to the strong microseismicities activities to be generated and the supporting pressure and surface subsidence significantly be increased. Fracturing of high and thick strata of hard rocks causes strong dynamic response which can be analyzed and predicted by theoretical calculation and microseismic monitoring. Source

Zhao L.,University of Science and Technology Beijing | Liu J.-H.,University of Science and Technology Beijing | Zhou W.-J.,Huaibei Mining Group Company | Ji H.-G.,University of Science and Technology Beijing
Meitan Xuebao/Journal of the China Coal Society

Some experiments were conducted to simulate the mechanical characteristics and deterioration of concrete under sulfate and wet-dry cycle environment. The parameters were tested and analyzed, including compressive strength, splitting tensile strength, bending strength, the variation of mass and ultrasonic velocity and stress-strain curves over attacked time. The damage development was evaluated by multi-index of attacked concrete based on damage mechanical theory. The relationship between the corrosion damage and stress-strain characteristics was analyzed. The damage model of corroded concrete was established considering the effects of the parameters such as corrosion time and strain on the damage evolution. According to the ESEM images and XRD results, the damage mechanism was obtained by analyzing the microstructures of concretes at different erosion periods. The research results show that: (1) Under the coupling action of sulphate attack and drying-wetting cycles, the parameters, including the compressive strength, splitting tensile strength, bending strength and ultrasonic velocity, increase first and then decrease with erosion time, and especially the splitting tensile strength and bending strength signature are more sensitive to damage and deteriorate more seriously. According to data regression, the corrosion damage evolution equations were developed. In the equations these performance indicators were regarded as damage variables. Linear functional relationship exists among different damage factors. (2) In the long term, with corrosion time the peak stress decreased while peak strain increased. Elastic modulus and deformation modulus also decreased. The damage caused by corrosion and the one caused by load were unified by means of mathematical model, which revealed the relationship between and among sulphate attack, load and damage to concrete in complex underground environments. (3) During the erosion time, the combined expansions of ettringite, gypsum and the crystal of sodium sulfate decahydrate cause micro fractures. With the increase of corrosion time, the micro-cracks developed and their number increased. © 2016, Editorial Office of Journal of China Coal Society. All right reserved. Source

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