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In order to solve the problem, that the hard rock fault with a large throw hinders the advance of a fully mechanized mining face, this paper analyzes the disadvantages of the traditional method for passing through the fault and the existing technologie. Also, the paper carries out a systematic study on the deep hole pre-splitting blasting tech-nology for passing through the fault with a large throw. Aiming at the problems of unclear occurrence of fault with a large throw and inaccurate designed path for passing through fault, it puts forward fault occurrence detection technology and the optimized layout for fault detection roadway. Based on the revealed information, the fault strike calculation model is established. Aiming at the problem that deep hole blasting technology is not suitable for working face and groove, it studies the key technology of pre-excavation blasting roadway, and puts forward the layout principle and calculation method of layout parameters of blasting roadway. It determines the scheme of deep hole pre-splitting blasting in blasting roadway, designs the construction method of ear chamber, and solves the problem of concentrated blasting with large amount of explosive. Based on the theory of rock blasting, combined with the characteristics of fault engineering with large throw difference, the blasting parameter selection and calculation method are completed by designing the hole diameter, hole depth, charge mass, plugging length, hole layout and blasting vibration safety control. The underground roadway of 2302 N working face at Xinjulong Coal Mine reveals a hard rock fault with a comprehensive drop 12. 5 m. Through the exposure points of lower roadway and six detection holes arranged in sequence, the initial strike of the fault extending to the working face is verified, and the vertical strike of the fault, the driving scheme along the floor of the coal seam and the driving scheme along the floor of the coal seam under the fault are designed. Based on the measured information, it plans the path through the fault. According to the change of fault occurrence in the path, it divides eight blasting regions, designs the blasting layout parameters in each region, and predicts and analyzes the blasting effect by means of numerical simulation. The application results show that the blasting fissure penetration effect is good, the consumption of shearer picks through the fault is reduced by 40%-50%, and the time is reduced to half compared with the time using traditional method through the fault. The technology for passing large throw fault have been successfully applied in many working faces in Xinjulong coal mine. It has achieved good results in ensuring high efficiency continuous mining, reducing the cost of passing through fault and ensuring blasting safety. The practice has proved that this technique is widely applicable in dealing with large throw fault at a fully mechanized mining face. [ABSTRACT FROM AUTHOR]

Based on variance theory and coal sampling basic formula, this paper analyzed main theoretical problems on coal sampling and derived their relationships quantitatively. In addition, the paper provides a clear guidance to coal sampling practice, which complements and enriches the coal sampling theory. The problems discussed include: lot precision estimation for sub-lots with the unequal mass, primary increment variance estimation under different mass of lots, coal mass on the influence of the sampling precision, the influence of the number of sub-lots on the sampling precision under the condition of constant number of increments taken from a lot, the relationship of the sampling precision with increment numbers for the same coal, increment numbers on the influence of the sampling precision for duplicate sampling, and the estimation of sampling precision for replicate sampling, etc. [ABSTRACT FROM AUTHOR]

Taking Tiaohu sag of Santanghu Basin as the research subject, this paper focuses on key problems of sequence stratigraphy subdivision and coal accumulation. Meanwhile it makes full use of the theoretical methods such as sequence stratigraphy of coal-bearing strata to discuss the coal accumulation of the Xishanyao formation. Detailed stratigraphic analyses of data from boreholes for the Xishanyao formation have been conducted in Tiaohu sag of Santanghu Basin and it is divided into three third-order sequences. Lowstand systems tract (LST), lake transgressive systems tract (EST), highstand systems tract (HST) are subdivided by the stacking patterns of stra-tigraphy, changes in lithology and lithofacies. A series of sequence-specific paleogeographic maps have been con-structed based on the contours of lithological parameters. The paleogeographic units include braided river, braided river delta and lacustrine sedimentary system facies. The preferred sites of coal accumulation is the transition region between braided river delta and lacustrine from the margin to the center. Furthermore, there are a range of thick coal seams at the contact interface between the delta front and the delta plains. The coal-accumulation features in sequence stratigraphic framework are clarified. Through analyzing coal seam change features, coal-rich zone, the accommodation rate in relation to peat production would have controlled on coal formation and preservation. During initial and late lake transgressive systems tract deposition, coal seams are thick and continuous while only thin, discontinuous and scattered coal seams are formed in the highstand system tract. The comprehensive coal-accumulation model is established based on the researches mentioned and the major coal seams are accumu-lated in the transition of the lake to the delta of the early and late EST. The results will not only provide a se-quence stratigraphical model and paleoenvironmental framework for understand of the whole Santanghu Basin for this interval, but also are of practical significance for after coal resources exploration in Santanghu Basin. [ABSTRACT FROM AUTHOR]

In this paper, ligent GIS system of underground coal mine,the intelligent development plan and the working face design, the intelligent roadway rapid drivage technology, the intelligent technology of fully mechanized coal face, the intelligent main/ auxiliary transportation technology, the hazard sources intelligent perception and early warning technology, the intelligent washing system,the intelligent comprehensive support technology, and the comprehensive control system and operating platform of mine Internet of things. Furthermore,the development direction of intelligent open pit coal mine was expounded. The development ideas of constructing the information system of open pit coal mine, developing the intelligent continuous mining technology of open pit coal mine, establishing the integrated space-air-ground safety warning system in open pit coal mine,and promoting the coordinated green development of ecological environment in open pit coal mine were put forward. It is important to vigorously develop intelligent manufacturing of coal mining equipment, improve the reliability and adaptability of coal mining equipment, promote the robotized substitution of coal resource development, and provide intelligent equipment support for intelligent development of coal mining. Some policy suggestions were put forward, such as increasing policy support for intelligent development of coal mine, setting up special projects for the intelligent standard system construction of coal mine,and establishing a national experimental platform for the intelligent technology innovation of coal mine. a scientific idea was proposed,i. e. ,the intelligent coal mine is the core technology support for the coal industry development. The definition and general requirements of intelligent coal mine were expounded. The development goal of intelligent coal mine is to build smart coal mine. The connotation and relationship of coal mine intelligence, wisdom, informationization and digitalization were analyzed. Also,the construction principles and goal of intelligent coal mine were proposed. The top-layer design of intelligent coal mine was carried out,and the ideas of the integrated planning development mode of intelligent coal mine, the scientific design on the overall framework of intelligent coal mine,and the construction of 100 intelligent demonstration coal mines were put forward. In addition,the main development routes of intelligent coal mine were discussed including the precision geological exploration and 4d- inteli [ABSTRACT FROM AUTHOR]

In order to achieve the technology for a large-scale ground control between sections and improve the stability of steeply dipping seam longwall face “Roof-Support-Floor” system, based on the analysis on the section of gob surrounding rock instability mechanism, this paper established an inter section rock instability model, researched the stress distribution law and instability criterion of the section coal pillar, and determined the rea-sonable size of the section coal pillar. The results show that the steeply dipping seam section of surrounding rock movement can be summarized as two modes of “extrusion-bend down" and “crush-dumping” . In order to realize this technology, the surrounding rock of the gob will lose stability in a “crush-dumping” mode. When the overburden structure exists in the form of “beam arch combined beam” , the strength of the section coal pillar determines the movement mode of the surrounding rock in the gob section. When the overburden structure is in the form of “double arch continuous beam”, the size of section pillar determines the pressure behavior characteristics of the “crush-dumping” mode and the gob’ s three-dimensional spatial form after the deformation and failure. Thus the key of this technology lies in the design of the section coal pillar. According to the strength and instability criterion of the section coal pillar, it is determined that the width of k must satisfy the k>kZH condition and meet the k>kSK condition as much as possible. In a case study at the multi-section mining of steeply dipping seam in Gansu DONGXIA coal mine, the comparative analysis of the theoretical calculation and similar simulation experiment was carried out, and the mechanism of the pillar instability was verified. [ABSTRACT FROM AUTHOR]

The flotation microscopic model considers that the attachment behavior of coal particles and bubbles is the key step to achieve flotation. Therefore, the direct research on attachment behavior is very important. A device was designed by ourselves to directly measure the attachment behavior of coal particles and bubbles. In this paper, the raw coal of Inner Mongolia Gongwusu was taken as the experiment subjects and the attachment behavior of 0. 1-0. 15 mm coal samples with different densities was directly observed. Then, it was analised by the multi-target tracking software. The results showed that coal particles would flowed around the bubble before collision occurrence, and the velocity and direction of coal particles would changed. The velocity of coal particles decreased to minimum when coal particles colliding with bubble. The sliding velocity of coal particles on the bubble surface firstly increased gradually, and sliding velocity reached the maximum at the bubble "equator" position. After crossed the "equator", the sliding velocity of coal particles gradually decreased, and finally coal particles attached to the bottom of the bubble. The attachment efficiency of coal particles and bubbles decreased with the increase of collision angle. At the same collision angle, the attachment efficiency and the critical attachment angle decreased with the increase of coal density. With the increase of terminal velocity, both the attachment efficiency and the critical attachment angle decreased. Therefore, the regulation of the attachment efficiency of different density was verified. [ABSTRACT FROM AUTHOR]

The rib spalling is a technical problem to be solved urgently in steeply dipping thick seam mining. Based on the geological conditions and characteristics of strata behaviors at No. 25221 working face in 2130 Coal Mine, the load and instability characteristics of coal wall is investigated by theoretical analysis, numerical simulation, physical analogue material simulation, and field monitoring. Results show that the asymmetry characteristics of mining pressure and strata behavior of large mining height face is higher than that of general mining height face in steeply dipping seam, which is due to mining height increase. Because the inhomogeneous characteristics of the overburden filling are further enhanced, the asymmetric characteristics of the supporting pressure of the coal wall are also obviously increased. During the process of mining, the mechanical properties of coal wall will gradually deteriorate, coal wall crazes and slip body appears. Then the slip body slides along the slip surface, rib spalling emerges, when the surrounding constraints of slip body are relieved or support pressure increases. In inclination direction, the central area is the high incidence area of rib spalling, upper secondary and lower minimum, which is consistent with the asymmetric loading characteristics of coal wall. Besides, in vertical direction, the displacement at the upper part of coal wall is larger than that at the lower part, and rib spalling is easy to occur near the roof area. And under the influence of the gravity tendency component of coal wall, the rib spalling is easy to spread to the upside. On the basis of safety production demands at No. 25221 working face in 2130 Coal Mine, some control measures have been proposed in the paper. [ABSTRACT FROM AUTHOR]

Trace elements in coal exist in many forms, most of which are combined with organic matter. Coal organic matter content also determines the degree of integration and the bound state of trace elements in coal. In terms of lignite, bituminous and anthracite coal, this paper analyzed the trace element content monitored by ICP-MS, studied the fluorescence spectroscopy characteristics of the dissolved organic matter (DOM) existed in coal using 3D-EEM Absorbance and Fluorescence Scanning Spectrometer, and conducted a further investigation on the relationships of DOM with the degree of coalification, the levels and status of trace elements in coal with a utility of PARAFAC system. The conclusions indicated that there was significant difference in trace elements. The highest content was ranked by As, Mg, Cd and Mn in lignite, while Li and Sr in anthracite. There was no significant difference in the content of Cu and Co. The fluorescence spectrum characteristics of dissolved organic matter revealed that only humic-acid fluorescence peak was detected in lignite and both the peaks of humic acid and protein in bituminous, while no fluorescence peak in anthracite. Also the fluorescence intensity decreased with the increase of coal rank. It was found that the occurrence of certain trace elements related with the dissolved organic matter in coal, which the higher fluorescence intensity of humic acid, the richer the contents of trace elements for As and Mg, while the rarer for Li and Sr. [ABSTRACT FROM AUTHOR]

In terms of the exploration of coal and coalbed methane,the advantage is a high exploration degree of coal and coalbed methane (CBM) and the disadvantage is a high overlap rate of mining right for CBM exploration and development in a coal mining area.Therefore,the study of spatial-temporal relationship of exploration and development is of significance for the safe and efficient coordination development of CBM and coal in a coal mining area.Based on the comprehensive analysis of the spatial-temporal replacement characteristics of coal and the present mining right situation of coal and CBM,with coal mine or exploration area as a basic unit,Huainan-Huaibei coalfield can be divided into seven different blocks.Based on the system analysis of the exploration and development sequence of CBM and coal and the development mode of CBM,combined with CBM geological conditions,with the spatial and sequence arrangement as mainline,this paper discussed the exploration and development principle of CBM and coal,the development mode of CBM,the distribution of key blocks,the gas bearing area,and the quantity of resource,and built up the pattern of spatial-temporal collocation for CBM and coal.The study provided a technical solution for the mining right overlap,and also provided a theoretical direction for the coordinated development of CBM and coal in Huainan-Huaibei coalfield. [ABSTRACT FROM AUTHOR]

In slime flotation, the flotation of coal is closely related to its surface wettability. In this paper, the lignite and coking coals with different surface wettability are investigated. The formation process of the three phases contact during the collision between bubble and coal surface is studied. First, the differences of the two kinds of coal interface properties are analyzed. At the same time, the I-SPEED 3 high speed dynamic camera is used to record and analyze the micro process of the collision and adhesion between air bubble and coal surface. Results show that under a certain condition of collision velocity, the bubble and coal surface should go through several collision process, contact-bounce-contact, and finally form the gas-liquid-solid three phase contact periphery. Three-phase contact surrounding is formed in the coking coal surface with bubble after the second collision, and the area is 8.2 mm2. Three-phase contact surrounding is formed after 3 times of collision in the surface of lignite, and the bubble in coal surface spreading area is 4.6 mm2. The greater contact angle of coal surface is, the shorter the three-phase contact formed around the time will be, and the greater bubble in the spreading area of coal surface will be. From the microscopic point of view, the effect of surface hydrophobicity of coal on the process of bubble mineralization is verified. [ABSTRACT FROM AUTHOR]

An analytic model of coal wellbore stability under non-uniform in-situ stress and drilling fluid pressure is established with the consideration of the random distribution of coal cleat and crack, and the coal near wellbore cutting into blocks. In this paper, the authors consider coal bed near wellbore as quasi continuum, and get the stress distribution of coal bed using continuum theory and rock fracture mechanics. The analytic form ula of block sliding , which is considered as a limit condition of coal wellbore collapse，is deduced. Considering positions and area of coal sliding block as control conditions, the PFC software that is one of DEM software is used to verify the accuracy of the analytical model. The results show that the bigger drilling fluid pressure is, the worse wellbore collapse is. Type I and type III block are extremely easy to slide，in contrast，type II block is not easy to slide and the sliding conditions of type II block is that the adjacent block should slide first. For the block that slide along the face cleat，the angle of internal friction and the cohesion of end cleat have little influence on block sliding. For the well named Qin 12-10-70-X ， when the drilling fluid pressure is about 9. 5 M Pa, borehole collapse has the lowest level, and the increase or decrease of drilling fluid pressure can intensify borehole collapse. [ABSTRACT FROM AUTHOR]

In order to establish a technical foundation for the investigation of the effect of the soluble compounds of small molecular organic-matters in coal with Sc-CO2 on the CO2 sequestration, and the development of a method of Sc-CO2 extraction biomarker in coal at a mild condition, an experiment apparatus of coal extraction with Sc-CO2 was built based on the interaction between supercritical CO2(Sc-CO2) and the organic matter in coal in the fields of greenhouse gas CO2 sequestration into deep and unmineable coal seams. The apparatus could be employed in coal extraction with Sc-CO2 in both static and dynamic extraction modes under the controlled conditions based on the low content of extracted matter in coal and easier penetration of coal dust into gas line. The paper describes in detail on the technique of CO2 pressure enhancement and coal dust control, the regulating method for extraction conditions, and the process of extract collection and enrichment. The apparatus consists of CO2 pressure enhancement, coal extraction, collection and enrichment of extracts. The apparatus can be used to carry out the Sc-CO2 extraction of trace amounts of soluble organic matters in coal at high pressure and under a controlled condition. [ABSTRACT FROM AUTHOR]

The study on rare metals in coal and coal-bearing strata is a hot point issue in the field of coal geology. Rare metals that could be highly-enriched in coal and coal-bearing strata and thus can be industrially utilized include Li, Sc, Ti, V, Ga, Ge, Se, Zr, Nb, Hf, Ta, U, rare earth elements (lanthanides and Y), and noble metals. In this paper, the geological origin, modes of occurrence, and evaluation methods for coal-hosted rare metal deposits including Ge, Ga, U, Nb, rare earth element ore deposits are reviewed. The study on coal-hosted rare metal ore deposits can not only provide important evidence of coal geochemistry and coal mineralogy for coal formation origin, coal-seam correlation, coal basin formation and epigenetic deformation, regional geology-evolution, and sudden geological event, but also are practically significant for the development of coal circular economy, environmental protection during coal utilization, and for the security of national rare metal resources. [ABSTRACT FROM AUTHOR]

Seismic while mining, using coal shear as sources, can achieve real-time coal face detection, however, the method of valid signal extraction of coal shear seismic data is still an issue. In this paper, using cross-correlation as the main data processing method, comparative study the wave field characteristics in different frequency bands while the shearer in different positions; also compared the effect of the reference signal detector in different positions; an initial detection of a known pitchout in-seams conducted using seismic while mining method. The study found that using cross-correlation interferometry can stably transformed shearer's continuous vibration into like-pulse shot-gather, and shot-gather has a higher signal to noise ratio in the 1-500 Hz band and 700 m propagation distance, where the wave-in-seam and roadway surface wave is the main phases, and the choice of the reference signal has a certain influence on the result of the interference. Studies suggest that using cross-correlation interferometry method can extract valid information from seismic signal of shearer; the energy and bandwidth are correspond with the requirements of seismic while mining. [ABSTRACT FROM AUTHOR]

Currently the seismic exploration technique is mainly used to reveal the structure of coal beds, and cannot be used to evaluate the distribution of deformed coal, the permeability of coal beds and their roof/bottom, which are related to gas outburst. In other words, it cannot evaluate the lithology of coal beds and rock strata. In recent years, some geophysicists suggest to investigate the lithology of coal beds and rock strata, and define the deformed coal distribution and gas concentrated area with AVO technique. In this paper, a 3D seismic cube of deformed coal model was initially obtained using seismic simulation. Subsequently, AVO inversions for the 3D seismic cube were calculated using different Zoeppritz approximate equations, and many AVO attributes were obtained. Through the analysis of AVO attributes, it was proposed that the B-value cube inversed with Aki & Richards approximate equation, and the G-value cube and Δσ cube inversed with Shuey approximate equation are used as the basis of AVO interpretation. Finally, AVO inversions for real 3D coal seismic data were performed to define the distribution of deformed coal and gas concentrated areas using AVO attributes. [ABSTRACT FROM AUTHOR]

An investigation was conducted on the characteristics of surface current induced by coal under uniaxial compression. An interpretation of the mechanisms governing the electrical behavior of the coal structures under uniaxial stress tests was presented in this paper. The experimental results show that the current signal is generated during the deformation and fracture process of coal samples. When the load is applied, the electric current makes its initial appearance and increases rapidly after a considerable time lag at 8C, until after the stress reaches a value δc ≈0.75δmax where δmax is the maximum applied stress before sample fracture. There is a good correlativity between the current and the load, and the correlation coefficient between them can reach up to 0.8 to 0.9. The current peaks occur under sudden loading and unloading. It suggests that the current is closely related to the loading. The status of coal loading level may be determined by the current signal. The intensive study on coal surface current can provide a way for monitoring the stability of coal and rock. [ABSTRACT FROM AUTHOR]

The paper introduced in detail the structure and function of μ225 kV micro-focus CT system with <3 μ m focus size and 0. 5 (xm resolution ratio, and 0. 3% density resolution ratio, which is the most advanced CT system in domestic and provided advanced equipment for micro-mecro structure research of rock. Using this system, pore and crack structure of coal in different temperature were observed, the research results indicate that, during the pyrolysis of anthracite from room temperature to 600 °C, the parameters of pore structure increase at the beginning and then decrease, the structure of pore change most acutely from 100 t to 200 °C, the quantities of the small and big pore all increase, the connectivity of coal goes up;at 500-600%, porosity and specific surface area decrease, connectivity falls; During the pyrolysis of anthracite from room temperature to 600 t, a lot of cracks grow up suddenly and the crack fractal dimension is the largest at 200 °C, during the temperature increasing gradually, the crack fractal dimension decreases gradually and the evolvement of cracks is mainly "extension-anastomosis-connection". [ABSTRACT FROM AUTHOR]

Taking into consideration the differences of disaster prevention in gas and spontaneous combustion of coal seam and goaf cross-scale fracture fields, the cross-scale fractures field of coal and rock mass were defined in this study. In addition, this paper studied the symbiotic disaster prevention and control mechanism, and technical change in cross-scale fractures field flow distribution, through the rational elimination of gas and coal spontaneous combustion symbiotic disaster, that is, the symbiotic region was equal to 0. The authors also proposed two new control technologies, which are: to change coal- rock fractures leakscale through solid-phase media transport, and to change the goaf temperature field and the gas concentration field through low-temperature liquid inert gas seepage. A network graph theoretical model of a particle transport of fine solid phases to change coal-rock fractures scale had been developed in this study, which reveals that solid phase media can be embedded.in the pneumatic transport blocking air leakage in the coal-rock fractureds field, to reduce air leakage fractures scale and the effective fissure numbers, and change the scale of coal-rock fractures leak field, as well as to increase air leakage resistance to ensure the safety of coal spontaneous combustion for high gas extraction. Also, the authors built an experimental simulation platform for investigating liquid nitrogen extinguishing characteristics, and the results show that the liquid nitrogen injected into the fire area can quickly cause heat expansion, resulting in a large number of low-temperature nitrogen pockets in the goaf, forming a three-dimensional buffer zone to reduce the external air leakage into the goaf or fire zone, to isolate the goaf or fire area. At the same time, the low-temperature nitrogen gas carries water vapor condensation into the goaf, exchanging heat with hidden heat source ( fire source), which can reduce the temperature of the heat (fire source) to below the temperature of flammable point and actively engulf the heat source (fire source). [ABSTRACT FROM AUTHOR]

Based on research results of motion parameters of coal-gas flow, this paper analyzes the formation mechanism of shock waves at different states of coal-gas flow in the coal and gas outburst process. While the ejected coal-gas flow has not exceeded the critical state, nor has it reached the state of low under-expansion, both the flow velocity after complete expansion in the roadway, and the overpressure of forming shock wave will be small. While the high or super high degree of under-expanded flow expands in the roadway, the flow will speed up with an explosive process if the roadway space is big enough. Conversely, if the roadway space is limited, the final overpressure of forming shock wave will be smaller, but the dynamic pressure of the two-phase flow and gas static pressure in the expansion process could seriously damage mine production equipment or facilities. The results of these tests are significant to the pre- warning and prevention of outburst disasters, the formulation of contingency plans, and the optimization of mine safety facilities. [ABSTRACT FROM AUTHOR]

This paper studies the characteristics of the breaking process of overburden rocks in shallow coal workface through physical analogous simulation, and obtains the key characteristics of overburden breaking process. Based on the field observation, the study finds the law between roof weighting and overburden fracture development. The results show that the breaking process follows the key points as the breakage of immediate roof, the initial breakage of main roof, the periodic breakage of main roof, the fracture belt's initial connectivity with the surface, and the fracture belt's periodic connectivity with the surface. The internal mechanism of roof pressure existing for long and short periods under shallow buried longwall working face is the fracture belt's connectivity with the surface, and the breakage of the main roof occurs periodically. During the mining process of shallow buried longwall working face, the breakage of main roof easily results in the fracture belt's connectivity with the surface. Therefore, in order to avoid the crushing accident of fully mechanized supports, the working face advancing speed should be accelerated during the period of the pressure change at working face. [ABSTRACT FROM AUTHOR]

To investigate the characteristics of adiabatic oxidation phase and build the prediction model of coal spontaneous combustion critical point, the adiabatic oxidation experiment data of eight coal samples are given in this paper, based on the adiabatic oxidation experiment, element analysis experiment and industrial analysis experiment. The phase heating rates of adiabatic oxidation of these samples are also calculated. Then using the thermodynamic parameter calculation method, Tr0.05 and TΔmax are defined and obtained. Furthermore, based on the Levenberg-Marquardt method, the relationship between the coal element content, volatility, the phase heating rate of adiabatic oxidation and Tr0.05 are established. The results show that the content of N or S correlates positively with Tr0.05 Osand that O, C, or H content correlates negatively with Tr0.05. However, the link between these elements and stage-heating rate is the opposite. The law also suggests that stage-heating rate will be much faster and coal spontaneous combustion will be easier when Tr0.05 becomes much lower. The more volatile coal is, the lower Tr0.05, and the more likely it is to spontaneously combust. [ABSTRACT FROM AUTHOR]

Based on the mechanical model of the coal-wall in extraction opening under high bearing pressure, this paper analyzed the basic distribution of the stress on the interfaces between the coal and rock and the axial force of coal. It first mechanically derivated the total horizontal displacement of the coal and established a new theoretical width formulas about the limit equilibrium zone in sidewalls. On this basis, discussed the main factors of the width without failure zone. The analysis results show that the stress and level pressure of the coal in the limit equilibrium zone distributes at the pattern of hyperbolic function. The vertical stress of the sidewall coal changes by the roadway height and mechanical parameters on the interfaces between the coal and rock. The horizontal displacement increases with the lateral pressure coefficient and peak stress of the elastic-plastic interface and the width of the limit equilibrium zone, while inversely proportional to the average elastic modulus of the coal. The width of the limit equilibrium zone depends on the external factors such as extraction opening depth, the average density of the overburden, the strength parameters of the interfaces between the coal and rock, stress concentration factor, lateral pressure coefficient, extraction opening height as well as composite elastic modulus of the coal. It increases with the addition of the extraction opening depth and extraction opening height and decreases with the addition of the internal friction angle and cohesion interfaces between the coal and rock. Finally, the rationality of these results were verified by an engineering example. [ABSTRACT FROM AUTHOR]

Employing a lot of lab tests, this paper investigated the impact of salt solution on the expansibility, the roller recovery rate and the permeability of coal rock samples collected from No. 3 coal seam in Jincheng. The impact of salt solution on drill pipe's corrosivity was also investigated. Here salt solution includes various types of salt such as NaC1, KCl, CaCl2, HCOONa and HCOOK with the concentration varies as 5%, 10% and 20%. The results show that: firstly, fresh water can bring formation damage to gas bearing coal seam when it is used as drilling fluid in coal seams with a high content of clay minerals; furthermore, in presence of salt solution, adsorption and swelling of coal rock matrix can be restrained and even the matrix can shrink, increase of weight percent results in better inhibitive performance when same type of salt is used; finally, with the integrative consideration on technology feasibility and economic cost, HCOONa and HCOOK have better inhibitive performances and lower corrosivity compared with other salts and the optimal concentration are 10%. [ABSTRACT FROM AUTHOR]

Based on depth study of the influence law of key strata on the height of fractured water-conducting zone, this paper proposed a new method to predict the height of fractured water-conducting zone by location of key strata. The engineering measurements and theoretical research results show that the key stratum location affects the height of fractured water-conducting zone in the roof, when the distance from key stratum to the coal seam is less than a critical value, the fracture of key stratum will develop to water-conducting fracture, and the same goes to the fracture of the overlying strata controlled by key stratum leading to a synchronous breakage with key stratum. The critical height of key stratum fracture can be roughly estimated to be (7 ~ 10) M, where M is coal mining height. When it is less than (7 ~ 10) M from the primary key stratum to coal seam, water-conducting fracture will grow to the location above the roof of the bed rock, then the height of fractured water-conducting zone is equal to or greater than the height of the bed rock. When the distance from the primary key stratum to coal seam is greater than (7 ~10) M, water-conducting fracture in the roof will develop to the position below the nearest key stratum being (7 ~ 10) M more away from the coal seam ,and then the height of fractured water-conducting zone equals to the distance of the key stratum to coal seam. The prediction method is able to predict the height of fractured water-conducting zone in the roof with different mining heights, meanwhile, it also can be utilized to distinguish the abnormal development of the height of fractured water-conducting zone induced by structural changes of key stratum, and its reliability is verified by engineering measurements results. [ABSTRACT FROM AUTHOR]

In order to effectively control rock burst disaster due to the process of corner coal pillar recovery, it is available to use the theoretical analysis and numerical simulation to analyze the overburden structural characteristics and induced mechanism and control measures depending on characteristics of isolated coal pillar with trilateral gob. It shows that isolated corner coal pillar working face with trilateral gob has anti-arc overlying rock structure composed of "T" and "Γ" structure, which can make the coal pillar form an anti-arc high stress and elastic energy accumulation district around the working face; the main reason which induced rock burst is that the cyclical movement of "Γ" structure leads to the anti-arc overlying rock structure being in the dynamic process and the comprehensive role of the static and dynamic stress affect the steady state of the coal body in the process of recovery. This paper puts forward the non-symmetric control countermeasures weakening the implementation of relief along the coal side of roadway and strengthening support to narrow coal pillar side, to reduce the impact of anti-arc structure of overlying strata and control the impact of risk. [ABSTRACT FROM AUTHOR]

Microscopic mechanism of adsorption heat's generation was expounded systematically. On the basis of the potential energy model, two-energy-state model was got and the computational formula of the corresponding adsorption heat was deduced. On the basis of the grand canonical ensemble theory, the Langmuir monolayer model of statistical mechanics was got, and the computational formula of the corresponding adsorption heat was deduced. This paper cited De Broglie thermal average wavelength, and got the approximate computational formula of adsorption heat based on the Langmuir monolayer model. To compare the two models, it shows that adsorption heat is much affected by the adsorption capacity, adsorption centers and the average distance between molecules, and that we should use different physical models for analysis towards the outer layer of methane (relative to the coal surface) and the inner methane. On the basis of the Langmuir monolayer model, from perspective of adsorption, the fractal features of pore structure and fracture structure was studied, the two-dimensional fiat surface adsorption to the fractal surface adsorption was extended, and a fractal dimension based on De Broglie thermal average wavelength was got. [ABSTRACT FROM AUTHOR]