China University of MiningandTechnology

Tongshan, China

China University of MiningandTechnology

Tongshan, China
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Li Y.,China University of MiningandTechnology | Pan Y.,Ordnance Engineering College | Yan R.,China University of MiningandTechnology
Mining Science and Technology | Year: 2010

The static correction of a near-surface model may be improved by using travel time tomographic inversion. We discuss unfavorable factors in the inversion of surface seismic waves that have been analyzed by the first break. These factors show that sources and geophones arranged on the surface, or close to the surface, give a first break that only includes the direct wave and the up going wave from the down going to up going transition. These up going waves have weak directivity when they arrive at a geophone and so the rays passing through the grids have small directional differences and a narrow azimuth. Drawing lessons from the advantages of Vertical Seismic Profiling (VSP) acquisition mode we describe a pseudo well-surface simultaneous travel time tomographic inversion of a near-surface model. The well depth should be increased in the surface seismic study to produce a pure up going wave, to enhance the verticality of the rays and to increase the azimuth and shorten path length of the rays. Simulations of the effect of well depth on a pseudo well-surface simultaneous travel time tomographic inversion model are reported. The results show that the static corrections are improved significantly when the well depth extends below the weathered or sub-weathered layers. The root mean square error of the statics is 1.14 or 0.93 ms for these two situations, respectively. © 2010 China University of Mining and Technology.


Lei D.,China University of MiningandTechnology | Li C.,China University of MiningandTechnology | Zhang Z.,Henan Polytechnic University | Zhang Y.,Henan Polytechnic University
Mining Science and Technology | Year: 2010

Based on the particularities of gas outbursts, i.e., low gas bearing capacity and low gas pressure in the "Three Soft" coal seam in western Henan, we applied the theories of plate tectonics and regional structural evolution to investigate the mechanism of this seam and its impact on the coal seam gas formation. Our investigation revealed that coal and gas outbursts are distributed in a strip in a NW direction, with a number of high-penetration mines scattered towards the south side and low-gas mines largely located on the north side. We analyzed the statistics of 38 gas explosions and the rock-coal sturdiness number coefficient f of 167 sampling sites in the region and found the gas outburst mechanism that features a "low indicator outburst phenomenon". The mechanism is characterized by structural coal as its core, a low gas bearing capacity, low gas pressure and sturdiness coefficient f mostly less than 0.3. Our research results provide a theoretical foundation for effective control of gas disasters. © 2010 China University of Mining and Technology.


Guo X.,Xuzhou Normal University | Ma X.,China University of MiningandTechnology
Mining Science and Technology | Year: 2010

In order to realize the prediction of a chaotic time series of mine water discharge, an approach incorporating phase space reconstruction theory and statistical learning theory was studied. A differential entropy ratio method was used to determine embedding parameters to reconstruct the phase space. We used a multi-layer adaptive best-fitting parameter search algorithm to estimate the LS-SVM optimal parameters which were adopted to construct a LS-SVM prediction model for the mine water chaotic time series. The results show that the simulation performance of a single-step prediction based on this LS-SVM model is markedly superior to that based on a RBF model. The multi-step prediction results based on LS-SVM model can reflect the development of mine water discharge and can be used for short-term forecasting of mine water discharge. © 2010 China University of Mining and Technology.


Wu D.,China University of MiningandTechnology | Zhao Y.,China University of Technology | Cheng Y.,China University of MiningandTechnology | An F.,China University of MiningandTechnology
Mining Science and Technology | Year: 2010

In this study we measured the ΔP (initial speed of gas emission) index with different gas concentrations of carbon dioxide (pure CO2, 90 CO2+10 CH4, 67 CO2+33 CH4, 50 CO2+50 CH4, 30 CO2+10 CH4 and pure CH4) of coal samples from the No.2 coal seam in the Yaojie Coal Mine, Gansu province, China. The effect of carbon dioxide concentration, gas composition, coal strength and particle size of coal samples on the ΔP index was investigated. The experimental results show that with gas of various compositions, the ΔP value of three samples were clearly different. The ΔP index of coal samples A, B and C (0.2∼0.25 mm) were 4, 6 and 7 with pure CH4 and 22, 30 and 21 when pure CH4 was used. Carbon dioxide concentration affects the ΔP index markedly. The ΔP index increases with an increase in carbon dioxide concentration, especially for coal B. Hence, the ΔP index and K (another outburst index) values tested only with pure CH4 for prediction of the danger of outburst is not accurate. It is important to determine the initial speed of gas emission given the gas composition of the coal seam to be tested for exact outburst prediction. © 2010 China University of Mining and Technology.


Zhang H.,China University of MiningandTechnology | Wang L.,China University of MiningandTechnology | Gao F.,China University of MiningandTechnology | Yang H.,China University of MiningandTechnology
Mining Science and Technology | Year: 2010

We adopt the concept of generalized plane strain to model a roadway in a stress field. This can avoid limitations caused by simplifying the stress analysis as plane strain. FLAC3D was used to investigate the maximum tensile stress and displacement of a roadway in a known stress field for angles, between the roadway axial direction and the maximum principal stress of 0°, 30°, 45°, 60° and 90°. This theory was applied to the analysis of an engineering case. The results indicate that stress and displacement of the surrounding rock increase as the angle, increases. This provides some significant guidance for a reasonable layout of roadways in a known stress field. © 2010 China University of Mining and Technology.


Ji J.,China University of MiningandTechnology | Zhang J.,China University of MiningandTechnology | Chen J.,Lanzhou University of Technology | Wu S.,China University of MiningandTechnology
Mining Science and Technology | Year: 2010

In order to study the evacuation behavior of miners during accidents, we analyzed the rational layout of a safe chamber, and improved evacuation efficiency. A visual model of evacuation was developed and used to simulate the evacuation process of mines, given their special underground environments. In our simulation, the working faces of a coal mine and nearby tunnels were divided into 0.5 m×0.5 m grids to reflect the location of occupants and obstacles. Based on a "flow potential of the occupant", we determined the direction of movement and routes of occupants. In the model, evacuation speed changed as a function of crowd density, with an average speed of 1.30 m/s. The model also takes into account detection time of the disaster and the personnel response time. Evacuation time, exit flow rate and evacuation path were obtained by simulation. The results indicate that using simulation technology can present a more visual evacuation process and show the behavior of occupants. Our establishment of a mine safety evacuation system has merit as reference value. © 2010 China University of Mining and Technology.


Luo Y.,China University of MiningandTechnology | Zhang D.,China University of MiningandTechnology | Wang Q.,China University of MiningandTechnology | Liu H.,China University of MiningandTechnology | And 2 more authors.
Mining Science and Technology | Year: 2010

Reliability and wear resistance of cutting picks play a significant role in coal mine exploitation with coal shearers. Tool bit separation, blade breaking, severe erosion of the cutting body and fatigue fractures are the main reasons for failure of cutting picks. We carried out carburization on a 30CrMnMo alloy to synthesize a new cutting pick material with improved mechanical properties and high wear resistance. The results indicated that carburization can effectively strengthen the surface of the 30CrMnMo alloy by forming a thick carburized layer and thus significantly improve the surface hardness and wear resistance. In addition, the excellent toughness of 30CrMnMo alloy as a substrate of cutting picks can prevent brittle ruptures and fatigue fractures under high impact stress conditions. The significant decrease in both frictional coefficient and rate of erosion of this carburized 30CrMnMo alloy suggests that this alloy is a potential material for cutting picks of coal shearers after rational carburization. © 2010 China University of Mining and Technology.


Song D.,China University of MiningandTechnology | Wang E.,China University of MiningandTechnology | Wang C.,China University of MiningandTechnology | Xu F.,China University of MiningandTechnology
Mining Science and Technology | Year: 2010

Rock bursts are serious natural disasters encountered worldwide in coal mining and rock engineering. In order to forecast rock bursts more effectively, a new rock burst forecasting index E, consisting of intensity and the number of pulses, is proposed, on the basis of abnormal characteristic symptoms of electromagnetic radiation (EMR) generated before rock bursts, combined with statistical theory. The index is distributed as a χ2 distribution with 2 degrees of freedom, i.e., E∼. Via this index, a quantitative comprehensive forecasting criterion of EMR was initially established. E values were calculated when the occurrence probability of the occurrence of a rock burst was 50, 70 and 90. Appropriate measures should be taken when using these values on the scene. Using EMR data collected in the Nanshan Mine of the Hegang mining area, we verified that the analytical result were consistent with actual situations. This index is of theoretical importance and as a reference for forecasting rock bursts in coal mines. © 2010 China University of Mining and Technology.

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