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Lu C.-P.,State Key Laboratory of Coal Resources and Mine Safety | Dou L.-M.,State Key Laboratory of Coal Resources and Mine Safety | Wang Y.-F.,Datong Coal Mine Group Corporation
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2010

By TDS-6 microseism (MS) test system, the MS effect of the compound coal-rock samples from Xinzhouyao Coal Mine was studied in the process of deformation, fracture and rockburst failure, especially the evolvement of MS frequency-spectrum before and after rockburst failure was revealed. Using SOS MS monitoring system, the MS activity patterns of working face 8929 of Xinzhouyao Coal Mine were measured. The achieved results are as follows. (1) The rockburst precursory signal shows low-frequency character, the shorter the interval time between precursory and mainshock signal is, the lower the main frequency is. The spectrum of mainshock signal is wider, but the low-frequency component (0-50 Hz) will increase obviously. The aftershock signal shows high-frequency feature. (2)The correlation between the events, the total energy and the main frequency of MS signals is negative. Especially when the pressure and rockbursts were induced by roof fracture, the main frequency of MS signals is lowest. (3) The main frequency of rockburst precursory signals is about 0-50 Hz by measurement in field, and amplitude is lower. The spectrum of rockburst signals is wider, and the low-frequency component (0-20 Hz) will obviously increase, simultaneously the amplitude reaches to maximum. After rockburst, MS signals show the high-frequency and low-amplitude feature, and main frequency is about 0-200 Hz.


Zhang Q.,China University of Mining and Technology | Zhang Q.,State Key Laboratory of Coal Resources and Mine Safety | Zhang J.,China University of Mining and Technology | Zhang J.,State Key Laboratory of Coal Resources and Mine Safety | And 4 more authors.
International Journal of Mining Science and Technology | Year: 2012

Based on the principle of fully mechanized backfilling and coal mining technology and combined with the Xingtai Coal Mine conditions, we mainly optimized the coal mining equipment and adjusted the coal mining method in the Xingtai Coal Mine 7606 working face for implementation this technology. Firstly, we define the practical backfilling process as the "(from backfilling scraper conveyor's) head to tail backfilling, step by step swinging up of the tamping arm, gradual compacting, moving formed backfilling scraper conveyor when the second tamping arm cannot pass and connecting the immediate roof by back material push front material movement". Meanwhile, the stress changes of backfill body in coal mined out area was monitored by stress sensors, and the roof caving law was analyzed by monitoring the dynamic subsidence of -210 west roadway of this face. The site tests results show that using this new backfilling and coal mining integrated technology, the production capacity in the 7606 working face can reach to 283,000 ton a year, and 282,000 ton of solid materials (waste and fly ash) is backfilled, which meets the needs of high production and efficiency. The goaf was compactly backfilled with solid material and the strata behavior was quite desirable, with an actual maximum vertical stress of the backfill body of 5.5 MPa. Backfill body control the movement of overburden within a certain range, and there is no collapses of major areas in the overlying strata upon backfilled gob. The maximum subsidence and speed were 231 mm and 15.75 mm/d respectively, which proved the practical significance of this integrated technology. © 2012 Published by Elsevier B.V. on behalf of China University of Mining & Technology.


LU Y.,State Key Laboratory of Coal Resources and Mine Safety | LU Y.,China University of Mining and Technology | TU S.,China University of Mining and Technology
Mining Science and Technology | Year: 2010

In order to study the rules of distribution in a plastic zone of rocks, surrounding a roadway, affected by tectonic stress, we first analyzed the mechanics of a roadway affected by tectonic stress and derived a theoretical formula for the plastic zone of rocks surrounding a roadway. We also analyzed the distribution characteristics of the plastic zone under different levels of tectonic stress, vertical pressure, cohesion and friction angle of the surrounding rock. Secondly, we used numerical simulation to analyze the range and shape features of the plastic zone of rocks surrounding the roadway, given different tectonic stress levels. Finally we used a rock drilling detector to carry out field measurements on the broken state of rock surrounding the roadway at the -700 substation and channels in the Xinzhuang mine of the Shenhuo mining area. Given the measured ground stress, we analyzed the relationship between tectonic stress and the distribution of this plastic zone. Our results show that the range of the plastic zone at the top and bottom of the roadway increases with an increase in tectonic stress and this increase is especially obvious at the roadway corner. © 2010 China University of Mining and Technology.


Zhai C.,State Key Laboratory of Coal Resources and Mine Safety | Zhai C.,China University of Mining and Technology | Hao Z.,State Key Laboratory of Coal Resources and Mine Safety | Hao Z.,China University of Mining and Technology | And 2 more authors.
Procedia Engineering | Year: 2011

Aiming at the shortcomings of the traditional sealing materials of borehole for gas suction such as yellow mud and cement-sand grout, which indicated that the traditional sealing materials of borehole are easy to shrink after sealing, the sealing length of borehole is short and the sealing quality is not satisfactory, and the sealing price of the highwater material and polyurethane are also high. In this study, taking cement as a base material, a new composite sealing material mixed by expansion admixture, additive, fibrin and coupling agent was developed and the sealing performance and expansion performance of the material were also studied and analyzed. At the same time, the microscopic image handling system was used to investigate the microcosmic structure of material. The studying results showed that the new composite sealing material possessed a good expansion performance and a definite fluidity convenient for grouting. The material after solidification could combine closely with the borehole wall, and there was certain strength and it was not easy to shrink. Additionally, the suction gas concentration by borehole sealing exceeded 40%. It can be seen that the sealing performance of the composite sealing material is advantageous. © 2011 Published by Elsevier Ltd.


Lu Y.,China University of Mining and Technology | Lu Y.,State Key Laboratory of Coal Resources and Mine Safety | Liu C.,State Key Laboratory of Coal Resources and Mine Safety
Mining Science and Technology | Year: 2010

In order to study the mechanism of bolt support and the behavior of strata in a coal roadway under tectonic stress, deformation and destruction of a roof, floor and sides were studied using an experiment in similarity simulation. We also studied the mechanism and types of bolt support functions in the coal roadway. The results show that with an increase in horizontal tectonic stress, the strata in the roof and floor of the roadway gradually separate and become shear failure areas. Coal in side walls moves, but its integrity remains intact. Side bolts are mainly affected by tension and roof bolts by the effect of shear. © 2010 China University of Mining and Technology.


Zhang J.-X.,China University of Mining and Technology | Zhang J.-X.,State Key Laboratory of Coal Resources and Mine Safety | Li J.,China University of Mining and Technology | Li J.,State Key Laboratory of Coal Resources and Mine Safety | And 3 more authors.
Meitan Xuebao/Journal of the China Coal Society | Year: 2010

Based on the analysis of the deformation characteristic of overlying stratum in fully-mechanized coal minning technology and backfilling with fully-mechanized coal minning technology, the mechanical model of key stratum in the raw waste backfilling with fully-mechanized coal minning technology was founded, and the bending deformation characters of the key stratum was analyzed by the theory of beam on elastic foundation. The maximum deflection and intensity of the key stratum, and the relation between lithological parameters and elastic foundation factors of the stratum below the key stratum was presented. According to the field geological conditions of a certain coal mine, the maximum deflection of the key stratum in backfilling with fully-mechanized coal minning face was calculated, and the relation between the deflection of key stratum and the elastic modulus of fillings was researched through changing the characters of the fillings. The research results provide that the bending deformation of the key stratum can be reduced by increasing the elastic modulus of fillings, and raw waste backfilling can restrict the deformation of the key stratum and the subsidence of surface can be controlled by raw waste backfilling.


Lang L.,China University of Mining and Technology | Fu-bao Z.,China University of Mining and Technology | Fu-bao Z.,State Key Laboratory of Coal Resources and Mine Safety
International Journal of Coal Geology | Year: 2010

The traditional identification of spontaneous combustion hazard of coal in China is unilateral and inaccurate, which is singly attributed to the properties of coal. Based on current research findings on coal fires, we've reconsidered the influential factors that lead to the spontaneous combustion of coal seams, and have ultimately built a comprehensive system for evaluating the hazard of spontaneous combustion. Applying holistic scoring method and Analytic Hierarchy Process, we integrated all of the factors into a quantitative model, and classified the ratings into five levels. Additionally, a Visual Basic 6.0 based application program has been developed to assist the evaluation, as well as three domestic colliery cases with varying fire hazards have been tested. Through practical application, the hazard evaluations have proved to be objective and valid, so the system is applicable to Chinese coal mines. © 2010 Elsevier B.V.


Miao X.-X.,China University of Mining and Technology | Miao X.-X.,State Key Laboratory for Geomechanics and Deep Underground Engineering | Zhang J.-X.,China University of Mining and Technology | Zhang J.-X.,State Key Laboratory of Coal Resources and Mine Safety | Guo G.-L.,China University of Mining and Technology
Meitan Xuebao/Journal of the China Coal Society | Year: 2010

The development course of backfilling mining technology was briefly reviewed, and pointed out two difficulties in developing the technology, that was to build the strata control theory in filling mining and to solve some technical approaches of transporting backfill to the goaf, the transport passage, the power and so on. Furthermore, the equivalent mining height method of the strata control in solid filling mining and the ground subsidence prediction was built. The principle and method of solid filling in fully-mechanized coal mining(SFFMCM) adapted to the traditional fully-mechanized coal mining(FMCM) technology was provided and the filling mining system and equipment self-developed were introduced at length. Industrial tests show that by using this technology not only can achieve the solid stowing to control strictly strata movement and ground subsidence prediction but also can achieve the economic benefit with high production and high recovery and environmental benefit.


Li Q.,State Key Laboratory of Coal Resources and Mine Safety | Li Q.,China University of Mining and Technology | Lin B.,State Key Laboratory of Coal Resources and Mine Safety | Lin B.,China University of Mining and Technology | And 2 more authors.
Journal of Natural Gas Science and Engineering | Year: 2014

Pulse hydraulic fracturing (PHF) is a new stimulation technique to enhance effectively permeability of coal seams, increasing the efficiency of gas extraction. However, the mechanism of PHF is still unclear, especially the effects of the key parameters. In this study, a series of experiments using a triaxial loading system were conducted to investigate the effect of pulse frequency on the fracture propagation and extension during PHF. The changes of pressure and acoustic emission (AE) energy rate during PHF were analyzed, and the relationships between frequency and pressure amplitude, fracture initiation pressure and duration were discussed. The results indicated that: (1) The changes of pressure during PHF can be divided into three periods: rising (R), plateau (P) and declining (D), and the P is the key period. (2) A lower frequency corresponded to a smoother pressure curve with a longer P period. In this case, the sample was "softened", the fracture initiation pressure was decreased and more complicated fractures may be created. A higher frequency corresponded to a more seriously fluctuating pressure curve with a shorter P period. In this case, fractures may be easily formed due to the rapid increasing of pressure. (3) The grading PHF could take both the advantages of lower frequency and higher frequency, and thus could strike a balance between the fracture extension effect and the working efficiency. This study can provide a foundation for the improvement of pulse hydraulic fracturing in coal mines. © 2014 Elsevier B.V.


Ying-ke L.,China University of Mining and Technology | Fu-bao Z.,China University of Mining and Technology | Fu-bao Z.,State Key Laboratory of Coal Resources and Mine safety | Lang L.,China University of Mining and Technology | And 2 more authors.
International Journal of Coal Geology | Year: 2011

This study investigates the deformation and the resultant pressure relief of highly gassy coal seams where a double seam mining operation takes place at lower depths at the Wulan Coal Mine, China. In order to predict the depressurization effect in the overlying coal seams, we simulate the extraction process by constructing a scaled model in the laboratory using similar rock materials. Analyses of experimental results concluded that due to the mining-induced stress redistribution, the pressure within target coal seams, which were 109. m above the mined seams, could be fully relieved to attain the statutory approval for gas drainage.In addition to scaled-model studies, computational modeling studies were conducted using UDEC (Universal Distinct Element Code), which showed that the features of deformation resulting from the double-seam extraction were different from that of in the case of single-seam extraction. The results of the numerical studies revealed that in addition to the panel margin on the air return side, areas near the intake entry could also be considered as borehole drilling positions. Besides, it was found that the gob of the extracted seams below the gassy one provided a "buffering effect" for the would-mined protective coal seam and that the depressurization effect was largely weakened.The laboratorial findings are instructive to the field practice of methane drainage. During the mining operation, a "displacement comparison method" was adopted to measure the dilated amount of protected coal seams, and as expected, the maximum dilation percentage was much more than 0.2% - the critical value upon which the target coal seam is appropriately depressurized to allow gas drainage to be safely and effectively implemented. © 2011 Elsevier B.V.

Loading State Key Laboratory of Coal Resources and Mine Safety collaborators
Loading State Key Laboratory of Coal Resources and Mine Safety collaborators