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Coal mining involves extracting the resources from the earth. It will disturb the strata in the mining area, which inevitably causes strata movement and the change of stress and fracture fields, thus affect safety and environmental such as the occurrence of ground pressure, groundwater loss and surface subsidence. Therefore, mining-induced strata movement and its influence on safety and environment are the basic scientific problems of coal mining. The understanding of these laws will improve the scientific nature of coal mining. Because of the complexity of strata movement, however, there are still several issues to be addressed. This paper introduces the mining-induced strata movement of the block structure, which is followed by the review of advances and outstanding issues in the influence of strata movement on longwall face support, mining-induced fractures evolution, groundwater, surface subsidence, and mininginduced stress field. It is found that mining-induced strata movement is a combination of stress concentration caused by the span of thick and hard strata and the mechanical behaviors of the rock blocks associated with the breakage of the strata. During the collapse of thick strata and the corresponding rock block movement, the characteristics of mutations and discontinuities typically occur. In such a process, a structure that can sustain large deformation may be formed after the rock blocks are hinged. The “R.-S” stability of the structure causes significant influence to such phenomena as the occurrence of ground pressure, mining-induced fractures and surface subsidence. Mining-induced strata movement is like a “black box” system. Currently it is just explained in the aspect of control principle, and reaches the level of a “gray box” system. Therefore, strata control refers to “macroscopic” control in many engineering cases. The Voussoir Beam model has established longwall support theory and the estimation principle of support working resistance. In a general case, the support resistance that is determined as the weight of the overburden with a thickness of 4 -8 times the mining height could meet the safety requirements of most mining projects. Specially,8 times should be chosen for the longwalls with a large mining height or a thin immediate roof, a shallow cover depth,or the support crush risks. As for some particular conditions, however, support crush cannot be avoided by the single measure of increasing support resistance, but should be combined with other engineering precautionary measures. According to the stability of rock blocks of overburden key strata, three types were proposed to characterize surface subsidence for varied alluvium conditions in different areas of China. It is suggested that subsidence type should be considered during the selection of subsidence prediction, control and reclamation methods. The presence of key strata and the corresponding breakage characteristics play a vital role in the distribution of mining-induced stress. At present, the prevention of accidents caused by stress concentration is harder than that of methane accidents. With this in mind, it is suggested that only test-style mines could be established in the areas with tectonic stress concentration or a large depth. This paper points out the direction for the study of strata movement and the corresponding influence on safety and environment in the coal mining industry. [ABSTRACT FROM AUTHOR]

In Yushenfu mining area, the concept of water-preserved coal mining is based on the groundwater level decline and vegetation degradation caused by coal mining in the early stage. After theoretical research and engineering practice in many years, a key technical system for water-preserved coal mining has been initially established, which effectively guides the exploitation of coal resources and ecological environment protection in the ecological fragile mining areas. Under the high standards for the construction of national ecological civilization, the ecological environment protection of coal-water resources symbiosis areas in the arid and semi-arid regions of western China is facing a historical test. This paper reviewed the achievements of water-preserved coal mining technology, and concluded that the research on geological conditions, rock movement and water-preserved coal mining methods had basically solved the outstanding problems in single coal seam mining, while the investigation on water and ecological constraints on coal mining, and ecological restoration and reconstruction lagged slightly behind. By combing the relevant contributions, this paper explores the scientific issues in the study of five water-preserved coal mining and related fields. This includes the ecological constraints identification, the quantification and monitoring of the groundwater dependent on the mining area, the detection and prediction of the water conducting fissure zone under the conditions of large mining height and repeated mining, the quantification and evaluation of the thickness of the effective aquiclude, the overburden control and ecological reconstruction and restoration. Under the new situation, the responsibility and tasks of ecological protection in mining areas are significant. More research is needed to support the water-preserved coal mining in western China and promote the construction of green mining areas. [ABSTRACT FROM AUTHOR]

A clear restoration algorithm based on deep fusion network is proposed to solve the problem of over enhancement and insufficient applicability of the existing dust and fog image clear restoration algorithm. The deep fusion network mainly includes three parts, namely, the image pre-processing module, the feature fusion module, and the image output module. The image pre-processing module processes the input image based on the contrast enhancement function, the brightness enhancement function, and the gamma correction function to obtain an image sequence that characterizes different enhancement modes and degrees. Because the local information and global information of image need to be taken into account, this paper proposes a double pyramid module which can realize a dual-path context information extraction on the basis of spatial Pyramid pooling and context information aggregation network. The module consists of two series sub-blocks of dilated convolution, one is composed of a series of small to large scale dilated convolution on multiple scales, and the other is composed of a series of large and small scale void convolution on multiple scales. The image output module mainly processes the features acquired by the feature fusion layer, thereby outputting a threechannel image, that is, a clear image. In order to obtain the training data, this paper builds a large-scale training data set based on the dust fog image formation mechanism with the clear coal mine images. In the process of training, this paper uses the least square error loss function and the content loss function based on VGG network to optimize the network. In order to evaluate the effectiveness of the proposed algorithm based on deep fusion network, six other representative clearing algorithms are selected for comparison. The experimental results show that the proposed algorithm outperforms the other six algorithms in subjective evaluation and objective evaluation, which indicates that the proposed algorithm can effectively solve the over-enhancement phenomenon and improve the clarity and visualization of coal mine images. [ABSTRACT FROM AUTHOR]

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]

Currently more coal resource is buried in deep and more high-quality resource is located in the west of China. It makes a deep mining and a mining in the west become the new normal of coal resources exploitation. Thus a green mine construction, green mining development and green mining propulsion are imperative. This paper puts forward a"mining-dressing-backfilling+X"technical conception of green mining of coal resources. That is an underground integrated production system, which is integrated coal mining, coal-waste separation, and gangue backfilling with "active control of strata movement, gob-side entry retaining, gas extraction, disaster prevention, water-preserved-mining". The system forms a coal mining-dressing-backfilling+X(control, retain, extraction, prevention and preserved) collaborative production mode. The paper defines the"mining-dressing-backfilling+X"technical connotation and framework of greenmining, expounds "mining-dressing-backfilling+X"evolution of four generations, analyzes the specific technical advantages of its practice of green mining and gives the scientific engineering design method. The paper elaborates five aspects of typical "mining-dressing-backfilling + X"technology corresponding technical principle, engineering requirements, design process and methods, key technology and process equipment. Engineering practice of the Tangshan Coal mine, Zhaizhen Coal mine and 12 th Coal mine of Pingdingshan Group has respectively proved that "mining-dressingbackfilling+ control", "mining-dressing-backfilling + retain", "mining-dressing-backfilling + extraction " technologies have a remarkable technical superiority and the engineering demonstration effect. "Mining-dressing-backfilling + X "green mining extension in the future combines "mining-dressing-backfilling+processing", "mining-dressing-backfilling+intelligent", "mining-dressing-backfilling+adjustment"and "mining-dressing-backfilling +coordination". The overall formation of the "mining-dressing-backfilling+X"technology system can provide a strong technical support for the realization of green mining of coal and associated resources. [ABSTRACT FROM AUTHOR]

Based on the full analysis of the present situation at home and abroad, this paper puts forward the concept and core content of transparent mine and five principles to be followed in constructing transparent mine.Based on the latest development of spatial information technology, the paper expounds the architecture of transparent mine system including three-dimensional engine layer, intelligent coal mine platform layer and production operation layer,and introduced the solutions of the key technical problems of three-dimensional spatial modeling criterion for coal mine, the storage and integration of multi-source spatial-temporal data, the construction and dynamic modification of high-precision geological models, the three-dimensional visualization of massive data,and mechanical and electrical equipment modeling and simulation and three-dimensional automated remote control. Those establish a solid foundation for transparent remote management and control of coal mines.Some technologies have been applied in Yangquan Coal Industry (Group) Co.Ltd. [ABSTRACT FROM AUTHOR]

The conventional study on scraper conveyor chain working condition only considers the bilateral same load chain working condition.This paper mainly studies the single side chain condition and its effect on the vibration characteristics of the scraper chain system torsional pendulum.The cause of the chain failure and the way of applying the load simulation are analyzed.Also,the paper investigates the mechanical model of scraper conveyor chain working condition,selects Voigt model to establish the dynamic model of scraper conveyor torsion pendulum vibration,uses Matlab software to establish dynamic equation and state equation,and constructs a function subroutine to the established dynamic equation.The preprocessing of dynamic analysis is realized.The vibration speed,acceleration and tension of the torsion pendulum of the scraper chain system are obtained by simulation analysis under four different working conditions of different materials before and after the chain position,and the experimental results are verified. The results show that the chain process will cause a strong torsion vibration of the scraper chain system,and the torsional pendulum vibration is more obvious when there is no material at the beginning.In the case of both front and rear materials,the vibration of torsion pendulum weakens slightly. [ABSTRACT FROM AUTHOR]

As a national strategy,deep resources mining has been of great importance.However,current theory,techniques and methods cannot satisfactorily solve the technical and environmental problems in deep mining.It is critical to reform the current methodology.Guided by the coal industry revolution and with an aim to solve the bottleneck difficulties for over 2 000 m deep mining,this paper systematically presents the scientific conception of deep in-situ mining,and the theory and technical system of fluidized mining for deep underground mineral resources.Specifically,four theories were depicted in this paper,including (i) mining induced rock mechanics,(ii) "three fields" visualization,(iii) in-situ multi-physics coupling and design,and (iv) the conversion and transportation of in-situ fluidized mining for deep underground coal resources.To support the four theories,ten techniques were provided,including ① geological safeguard,② accurate exploration and navigation,③ intelligent development and layout of mines,④ intelligent coal washing,⑤ in-situ intelligent mining-preparation-backfilling and conversion of electricity-steam-heat,⑥ intelligent transport and lifting,⑦ energy-induced physical fragmentation,⑧ in-situ chemical conversion,⑨ in-situ biological degradation,and ⑩ in-situ pulverized coal deflagration power generation.Finally,the strategy of deep in-situ fluidized mining was developed. [ABSTRACT FROM AUTHOR]

Rock burst occurring in deep coal roadway is a technical problem to be solved, 85% of which occurs in the roadway, and its frequency and intensity increase dramatically with the increase of mining depth. This paper analysis the instability mechanism of deep coal roadway roof based on the elastic-plastic mechanics and fracture principle, expounds the rupture instability mechanism of roadway roof strata with increasing stress and energy, derives the load, deformation and energy conditions of rock burst, and elaborates the fission instability evolution law of composite roof which turns roof into the vicious circle of "interlayer separation-rock beam cracking-dynamic crack by dynamic load" or even instant caving. The instability process of deep coal roadway roof is closely related to the cooperatively extension of six main cracks under the superposition action of high stress and dynamic pressure. The six cracks of "one horizontal and five vertical" extend together and form a "door" -like breaking block to push into roadway and cause damage. The paper presents the six manifestation pattern of rock burst and dynamic instability, puts forward the effective unit control timbering countermeasure of ‘‘roof truss cable+roadway center long cable+roadway drift angle bolt”. [ABSTRACT FROM AUTHOR]

Goal rock is naturally comprised of a large number of randomly-distributed discontinuities such as joints/ cracks and weak interlayers. The geometry, size, distribution, contact and infillings of the discontinuities essentially govern the physical/mechanical properties and failure mechanism of coal rock. It is intractable to theoretically and accurately characterize the discontinuities and the governing influences on the deformation and failure of coal rock. This paper presented a 3D finite element model of fractured coal rock representing the irregular geometry, complex contact, intersection, and network features of interior joints and cracks by means of high-resolution GT techniques and 3D reconstruction methods. The birth-death clement algorithm was employed to characterize and visualize the stress field distribution, spatial distribution of failed areas, energy dissipation and release during the deformation and failure of fractured coal rock when subjected to the varied unloaded conditions. The analysis discloses the determinative influences of the unloading paths and the properties of joints and cracks on the macro mechanical behavior and the failure mechanism of fractured coal rock. The paper presents a promising way to identify and characterize the governing effect of unloading due to deep excavation on real fractured coal rock. [ABSTRACT FROM AUTHOR]

For single-phase grounding faults in coalmine high-voltage power network, application and deficiencies exist in grounding protection principles, also the valuation and time limit coordination of selective protection are not easy to be satisfied between upper-stage and lower-stage, so grounding protection act without selectivity. A share of the underlying data of the whole station can be realized by intelligent substation, which providing a new opportunity to resolve the problem of grounding protection act without selectivity. Using quadrants which the zero-sequence total currents in as judgment basis, comprehensive protection criterion using fault information collected from multi branches was studied in this paper, PSCAD simulation results have verified that this method can ensure the transverse selectivity. A fault section location method based on optimal matrix algorithm was studied in this paper, network structure matrix and fault information matrix were constructed first, then fault judgment matrix was calculated to judge fault section, the superiority of this method was proved by the numerical example and PSCAD simulation. The implementation scheme of selective grounding protection based on coalmine intelligent substation was discussed, including the structure of multi-area centralized control coalmine intelligent substation and the process of selective grounding protection realization. [ABSTRACT FROM AUTHOR]

Coal mining in Jurassic coalfields of the arid Northwest area has damaged the local water resources greatly. Basing on the analysis of diachronic changes of the drainage and water balance of Jinjie Coal Mine, the paper gave some explanations of the changes of circulation patterns of groundwater before and after the mining. According to the changing characteristics of the water levels of pore water, fissure water and mixed water of double aquifers before and after mining, it was believed that the variation of the hydraulic properties of the roof aquifer in the mining area is mainly induced by the unified evolution of the transmission and closing property of roof aquifuge during the promoting process of mining face. The variation of the transmission and closing property of roof aquifuge changes the circulation pathways of mine groundwater, and the heavy-water deposits could be formed in the arid area. Also, the paper holds that the prediction method of real-time mine inflow based on variations of roof hydraulic properties will be one of the key issues in the future studies of deposit hydrogeology. [ABSTRACT FROM AUTHOR]

To solve the problem of high dust concentration caused by rock tunnel excavation, in view of the characteristics of dust produced and analyzing the processes of roadheader cutting rock, the paper used Fluent software to carry on numerical simulation of dust movement and analyse the dust characteristics of motion and concentration distribution. Simultaneously, this paper designed the foam dust suppression system applied to fully mechanize large cross-section rock tunnel excavation on the principle of foam dust suppression, and put it into application at the driving face of the north main haulage roadway in Zhuxianzhuang Coal Mine, Huaibei Mining Co., Ltd. The results show that the dust concentration on the exhaust section of the driving face, reaches a maximum at the leeward side of dust source. Foam making by the foam dust suppression system can enclose roadheader's cutting head and cover palisades, reaching the results of wetting rock, reducing dust content, depressing the generation of dust and blocking the spreading alleyway. The average dust-settling effect is 86. 2% and 84. 4% for the total dust and respirable dust, and the effect is 3. 6 and 4. 6 times comparing with water spray, achieving a good effect. [ABSTRACT FROM AUTHOR]

In order to effectively control gas unbalance phenomenon of gas occurrence in coal mine, this paper put forward the concept of gas enrichment area and gave the general characteristics of gas enrichment area. Based on geological condition in Zhaogu No. 1 Coal Mine, the paper discussed the gas geological features and analyzed the formation mechanism of gas enrichment area in the thick loess-thin bedrock coal seam, and then obtained the recognition method of gas enrichment area by the overlying bedrock characteristic of coal seam. On the basis of which, the gas enrichment area of Zhaogu No. 1 Coal Mine was confirmed, that was the bedrock layer thickness greater than 50 m and coal seam overlying bedrock gradient greater than 0. 06 or the bedrock layer thickness greater than 150 m area. Coal mining practice verified gas enrichment area identification and actual gas occurrence consistency. [ABSTRACT FROM AUTHOR]

Goaf roadway poses a vital threat to coal mine safety and miner’s life. The scale of the goaf roadway volume is relatively small, therefore, the ordinary geophysical prospecting method can hardly detect it accurately. Also, the drilling method can rarely hit the target precisely. For the purpose of detecting the goaf roadway more precisely, a roadwayborehole transient electromagnetic method( TEM), belonging to a 2 D operating method with fixed source and dynamic reception device, was proposed. This method, by arranging a fixed transmission cable over the borehole and shifting a receiving probe along the borehole to implement three-component observation, realized a high-precision detection for the borehole radial geological anomalous bodies. The device, with more complex observation curve, had harder inversion difficulties. By analyzing the data characteristics adopting asynchronous parallel GPU plus CPU finite-different time-domain 3 D numerical simulation method, this paper presented a related sliding time window wave-field inverse transformation algorithm, combined the both advantages of time segmentation and full time wave-field transformation algorithm, to transform data with higher accuracy. By studying the characteristics of time-distance curve of 2 D transient electromagnetic virtual wave field data, a corresponding dynamic correction algorithm was derived. By adopting equivalent conductive plane method, initial velocity model was constructed. Ultimately, based on virtual acoustic medium hypothesis, the roadway-borehole TEM data pseudo-seismic inversion was realized by the means of conjugate gradient full-waveform inversion technique. The inversion results of 3 D numerical simulation, flume simulation experiment and coalmine on-site simulation data showed that it had acquired favorable effect in exploring small-scale anomalous body on the radial direction of the borehole. In order to test the practicability and availability of this operating method in detecting water-logged goaf roadway’s shape, characteristics and scale, the author’s research group has conducted an case study in Shanxi’s coal mine. The research showed that the roadway-borehole TEM detection method is a great combination to underground geophysical exploration technology and drilling technology, and to make them supplement to each other. It is an effective application in goaf roadway with water detection. [ABSTRACT FROM AUTHOR]

The change of coal permeability related to gas pressure is important to coal mining and CBM exploitation.The permeability evolution of various kinds of coal is different and changes with stress conditions. To investigate the permeability evolution of coal samples changed in gas pressure, the strain and permeability of coal samples collected from the No.9 coal seam in Zhaogezhuang mine,Kailuan,China were measured during gas pressure reduction under constant temperature, axial and confining stress by using Triaxial servo-controlled seepage rig.The experimental results showed that coal shrinkage strain increased with the decrease of gas pressure.And the permeability of coal cores may increase gradually or decrease firstly and then increase( The gas pressure cor-responding to permeability rebound is less than 1.0 MPa).When the gas pressure reduced to 0.3 MPa,the perme-ability was 1.9-2.9 times of the initial condition( gas pressure was 2.0 MPa).Considering that coal axial and radial strains are approximately equal,a theoretical model was established to describe the permeability evolution of the three-dimensional deformation coal.The model also reflected the effects of gas pressure and gas desorption on coal permeability.The analysis showed that in the process of reducing gas pressure, the permeability of coal will change from decreasing to increasing at a certain gas pressure( rebound gas pressure pr). The equation of rebound gas pressure pr was derived.It indicated that prwas determined by coal volume modulus ,K, and Langmuir coefficients related to the adsorption, εpand pL.The greater volume modulus K and the adsorption deformation coefficient εpare, the higher pris.And prwas independent of the external stress and the internal gas pressure. According to the derived permeability model, the permeability curves and the rebound gas pressure pr of coal samples under various stresses and gas pressures were calculated by referring to the experimental data of this paper and other published articles. The numerical results were close to the experimental data with a maximum relative error less than 8.9%.The trend of coal permeability changing with gas pressure in the experiment depends on the rebound gas pressure prand the experimental gas pressure.When pr≥pmax( the maximum gas pressure in the experiment), coal permeability decreases with gas pressure increasing.When pr≤pmin( the minimum gas pressure value in the experiment), coal permeability increases with gas pressure.When pmin

Under the influence of open-pit mine stripping and internal backfill,there is a significant difference between the roof structure, overburden rock activity law and mining press show rule in longwall mining face of open-pit slope mine,which is different from the conventional formation condition working face. Therefore, calculation method of roof pressure also needs to be studied theoretically and experimentally according to the special roof overburden structure characteristics and stress field environment of the open-pit mine slope coal. The west side slope and south side slope coal seam in heidaigou open pit No.1 mining area is research background. The characteristics of the side slope coal seam roof overburden structure are analyzed. The coal seam at the low open-pit bench is internal backfill, and the stripping is more.This thinner and lower strength bedrock roof is covered with massive loose dumping.There is essentially no key stratum in the roof of the thick loose overburden of the weak thin bedrock. The weak thin bedrock under the bench of open-pit mine only provides a limited protective effect as immediate roof of longwall mining face.The crushing of weak the thin bedrock is also more serious because of the thick loose dumping loading.According to the traditional underground pressure theory,the roof pressure calculation of the thick loose overburden of the weak thin bedrock with no key stratum should be calculated according to the weight of all rock stratum above the support.However, according to the experimental results of similar materials, the actual pressure of the support is much smaller than the weight of the rock stratum above it.Experiments show that some protective structures still exist in roof strata with no key stratum.Based on the experimental observation and the analysis of underground pressure theory, combined with drawing theory, a hybrid model of the thick loose overburden of weak thin bedrock is proposed. The model is composed of the ellipsoid arch structure and the self-stability of immediate roof.In the open-pit mine slope coal, there are also another with no internal backfill roof overburden types of thin bedrock without overburden.For this roof overburden type,a hybrid model of thin bedrock without overburden is proposed. The model is composed of step cantilever beam structure and the selfstability of immediate roof.This paper summarizes the types of three roof overburden in the open-pit slope coal,and deduces and establishes an analytical formula for calculation method of roof pressure under the condition of three roof structures in longwall mining face of open-pit slope mine. According to the hybrid model of the thick loose overburden of weak thin bedrock,that is, the roof pressure calculated by the hybrid mechanical model combining ellipsoid arch structure and the self-stability of immediate roof is consistent with the result of similar materials experiment.Considering the self-stability of immediate roof of the calculation of the roof pressure than the traditional do not consider the self-stability of immediate roof of the roof pressure is about 14% less. Using experimental and theoretical analysis methods, the problem of ground pressure, such as roof caving,overburden strata movement,roof pressure calculation and so on, is systematically studied in longwall mining face mining process of open-pit slope mine. [ABSTRACT FROM AUTHOR]

Aimed at the challenges, such as long overhanging top-coal, poor cavability, low recovery and incoordination of coal cutting and coal drawing,faced in longwall top coal caving( LTCC) mining with extra-thick and hard coal seam in Yushen mining area, the authors discussed the feasibility and necessity of LTCC operation with super-large cutting height( greater than 6.0 m), and analyzed the coupling between hydraulic roof support and surrounding rock. Based on the coupling of strength, stiffness and stability of support-surrounding rock, a structure coupling theory of support-surrounding rock in LTCC mining with super-large mining height is put forward. The concepts and theories of "small structure" primary coupling, active supporting, and "large structure"secondary coupling,passive bearing,in the support system of hydraulic supports and the surrounding rock are explained from the perspective of the interaction mechanism between them.The authors analyzed the influence of "large and small structure"coupling of surrounding rock on the supporting effect and adaptability. It is pointed out that the structural design of hydraulic support used in LTCC not only needs to meet the requirement of adaptation of small structure supporting system to the strong dynamic load caused by periodic failure and instability of large structure, but also needs to consider the influence of the structure of hydraulic support( especially the structure of coal drawing mechanism) on the caving and migration law of hard topcoal,as well as the load evolution process of the support. The coupling between the structure of hydraulic support and the structure of caved top-coal can realize a smooth drawing of top coal and improve the recovery rate of top-coal.The methods of theoretical analysis, similarity simulation, numerical simulation and field investigation are adopted to analyze the caving and drawing structure of hard top coal and the arching effect during the coal drawing process. The influence of the structure height of hydraulic support on the caving structure and resource recovery rate of the top coal is discussed. The effect of caving mechanism structure on the arch structure of top coal and the secondary crushing effect of caving mechanism structure on top coal are studied. The structural improvement and optimization strategies of the strong coal drawing mechanism are put forward, and the mechanism and effect of coal breaking are discussed. This paper would provide guidance and reference for the coupling theory of hydraulic roof support and surrounding rock in similar hard and extremely thick coal seam. [ABSTRACT FROM AUTHOR]

The distribution and evolution characteristic of the stope pressure is a key factor to controlling sur-rounding rock in underground coal mining. The whole life cycle of stope is referred to the entire process from first cut to the termination of mining operation in this paper. The stope pressure consists of two parts including the advanced abutment pressure and mining face roof pressure. Aiming to analyze the dynamic evolution characteristic of the stope roof pressure, UDEC simulation analysis and different surrounding rock mechanical models of over-lying strata at corresponding multi-time-space conditions were applied. It is demonstrated in this study that the maximum advanced abutment pressure occurs earlier under time dimension and spatial dimension, as compared with the mining face roof pressure during a single periodic weighting process. When the mining face has advanced to the critical extraction point, the advanced abutment pressure and mining face roof pressure reach their extreme value successively. Thus, the whole life cycle of stope can be divided into three stages, which are initial stage (I), growing stage (II) and stable stage (M). The initial stage (I) corresponds to the period from first cut to first weighting,in which the stope stress increases softly. The growing stage (II) is from the periodic weighting to the critical extraction point between non-fully mining disturbance and fully mining disturbance. From critical extraction to the finish line is defined as stable stage (ID). During stage II, the stope stress increases faster than that in stage 1, and during the last stage HI, the stope stress changes stably. According to the dynamic evolution of stope pressure featured in life cycle of stope, it could be used to predict the high stressed zone, and the reinforcement support or pressure-relief methods could be applied and adjusted in advance, which can provide a safer mining environment. [ABSTRACT FROM AUTHOR]

The protection and utilization of groundwater resources in coal mining process is the prerequisite and necessary condition for realizing green mining at the ecological fragile mining area in western China. Among them, the extensive application of water-preserved mining and underground reservoir technology provides the possibility for solving the problem of coal-water co-production. In this paper, with the background that the stability of the coal and rock boundary of underground reservoir changed under the conditions of repeated immersion in water, the sandy mudstone of the No.3-1 coal seam roof of Wulanmulun Mine was investigated. The natural water absorption law of the sample was obtained by non-destructive water immersion test, and the water immersion time of the sample water content reaching saturation state was obtained. According to the immersion time, the sample was dried-saturated and repeatedly immersed in water. It was found that the water content increased exponentially with the number of immersion, whereas the shear strength and the number of water immersion in the sample decreased exponentially. The cohesive force decreased with the increase of the number of immersion times, while the internal friction angle increased first and then decreased, indicating that the uniformity of the material, and the shape of the fracture surface and the shape, size and direction of the fracture caused the internal friction angle to increase. The cycle immersion later was the dominant factor to make the internal friction angle decrease. Based on the relationship between cohesion, internal friction angle and number of dry-saturated cycles, the Mohr-Coulomb criterion was established based on the number of dry-saturated cycles. The acoustic emission counting curve had a strong correspondence with the shear stress curve. The acoustic emission event increased significantly at the moment of sample failure, corresponding to the obvious rising phase of the cumulative acoustic emission counting curve. The sample mainly had a low RA value during the failure process, and the failure time corresponded to a high RA value, i.e. , the common type of crack in the failure process of the specimen was tensile crack, and the moment of failure corresponded to the obvious shear crack. These results show that the strength of coal and rock pillars in the groundwater reservoir boundary changed significantly under the action of water immersion-water loss during the impoundment-pumping process in the groundwater reservoir. It is suggested that the weakening effect of water on the strength of boundary coal and rock pillars should be considered when constructing the underground reservoir. [ABSTRACT FROM AUTHOR]

In order to explore the hydrogeological conditions of the Cretaceous Luohe Formation in Binchang mining area, this paper proposed the Luohe Formation’s refined exploration concepts from the perspective of water-preserved coal mining, gave a comprehensive water-rich index method which can be used to evaluate the vertical water-richness of confined aquifers. The Luohe Formation was layered according to vertical water-richness. Luohe formation’s vertical hy-drogeological conditions and characteristics, hydraulic connection between the vertical aquifers of Luohe formation before and after mining, and the significance of water-preserved coal mining of the lower aquifer of Luohe formation were studied. Calculation method of water-rich index is given as follows:the indexes of lithology, thickness and porosity are assigned, and their weights are 0.3, 0.4, and 0.3 respectively;the value of water-rich index（fi） can be obtained by the cumulative multiplication of values of indexes and weights;then, the comprehensive water-rich index of each layer can be obtained using the following formula Fi=0.5fi+0.15fi-1+0.1fi-2+0.15fi+1+0.1fi+2. Grading standards of comprehensive water-rich index for aquifers in Luohe Formation are given:F<0.003 289 is aquiclude, 0.003 289≤F<0.012 339 is weak water-rich, 0.012 339≤F<0.015 504 is medium water-rich, and F≥0.015 504 is strong waterrich. According to the comprehensive water-rich index, the Luohe Formation of T1 and T2 drilling in Gaojiabu mine field were divided into the upper, the middle and the lower aquifers vertically. The results shows that:（1）the comprehensive water-rich index method could be used to evaluate the vertical water-richness of a confined aquifer, and it is simple and easy to use. （2）Mudstone formations were found in Luohe aquifer in some areas, but have not yet formed an aquiclude in the area. （3）The lower aquifer of Luohe formation could not only slow down the destruction of the upper and the middle aquifers structure from water flowing fractured zone, but also prevent the water inflow which was from the upper and the middle aquifers from entering working face. It is beneficial to protecting the groundwater of Luohe aquifer during coal mining;（4）During mining the first face of Gaojiabu mine, the controlling height of coal mining was used to protect the groundwater of Luohe aquifer, and the groundwater level in the middle and upper aquifers of the Luohe formation decreased by 26.71-43.06 m. Through the analysis of groundwater volume, water level, and water quality, it have achieved the goals of protecting the aquifer’s structure of Luohe formation and safely mining the deep coal seam. [ABSTRACT FROM AUTHOR]

Yushenfu coal field is located in the Maowusu Desert and the Loess Plateau convergence zone in China, where ecological environment is fragile and ecological water resources are scarce. The heterogeneous distribution of main aquifers and mine water inflow influence the safe production of coal mines. Thus, the protection and uti-lization of water resources are of significance to coal mine production and ecological construction. After analyzing the distribution and water abundance of the main aquifers, such as Salawusu Formation, burnt rock and weathering bedrock, combining the thickness of overlying bedrock and water inflow on field, the operating coal mines and unplanned areas could be divided into four types which are the areas of water scarcity, water richness, water abundance and surface water source. The study area has been divided into sub-regions according to the classification and their distribution. Based on the classification, the concrete measures for water preservation and mine water utilization have been proposed such as storage and purification in goaf area, industrial utilization, agricultural irrigation, wetlands construction and artificial lakes. In the paper, the scientific content of water-preserved mining has been extended and interpreted as that both preserving shallow main aquifers and effectively utilizing coal mine water resource should be taken simultaneously. It proposes that mining damage and ecological self-repair should be considered before coal mine construction. It also proposes that the idea of using economic benefits to repay the local ecosystem and green economy which provides certain references for mining area planning and construction. [ABSTRACT FROM AUTHOR]

The exploitation of underground coal resources can easily lead to the loss of precious shallow water resources, which leads to the death of surface vegetation and the imbalance of ecosystem. To protect the shallow water resources( river, lake and diving of quaternary sand aquifer), which maintains the ecological environment of the western mining area, especially to protect the underground diving( ecological) water level, the concept of water conservation mining in short-distance coal seams was put forward based on the previous theoretical achievements of water conservation mining in shallow single coal seam and the experience of rock control engineering. The concept integrated the protection of ecological water level, and the prevention and control of water inrush. In order to achieve an efficient water conservation mining under the mining conditions of short-distance coal seams and extremely short-distance shallow water resources, this paper studied the technical problems, such as the collaborative control of strata water-conducting fractures in the disturbed area of repeated mining, the low-damage control of ultra-thin barrier layers and the monitoring and warning of water inrush( outburst) on mining surface. The study presented the long wall water conservation mining method, the water conservation mining under continuous mining and filling with wall system and the infrared monitoring and warning methods for water inrush in working face to realize the safe and efficient mining. More specifically, the methods included the strata control of short-distance coal seams, the calculation of the height of water-conduct fractures, the deformation calculation of aquicludes, the infrared radiation theories of loaded coal and rock, the control of water diversion fractures in the disturbed area of repeated mining, the filling body actively connected to the roof and the rapid operation technology among mining, supporting and transportation. Meanwhile, the weak areas of water conservation mining were determined. Based on water resource protection, the optimized working face layout of shallow buried and short-distance coal seams, mining method allocation and water resource movement monitoring, an efficient mining theory was formed. The achievements have been achieved in the practice of water conservation mining in north Shaanxi and north China, which provides supports for green mining in China. [ABSTRACT FROM AUTHOR]

Vegetation distributed in arid and semi-arid regions, due to insufficient precipitation to maintain long-term survival, requires groundwater to provide part or all of its water demand, and thus is phreatophyte. When the underground mining destroys the aquifer, the groundwater level will drop significantly, which will cause water stress to phreatophyte, and control the ecosystem evolution process. In this paper, the authors investigated the basic characteristics of groundwater level change caused by coal seam mining in Yushen mining area, and proposed a method to determine groundwater level threshold under ecological constraints in mining area. As long as the roots are in contact with the groundwater capillary rise zone, the groundwater can be utilized by plants. Therefore, the sum of the maximum capillary rise height and the root length is regarded as the maximum critical depth of the groundwater. Under the guidance of capillary flow theory, the formula to calculate maximum capillary rise height is established by the relationship between particle arrangement and pore diameter, and the method of determining the maximum capillary rise height by particle gradation curve is given. According to the calculation, the maximum capillary rise height of the Mu Us aeolian sand is 0.7-2.0 m and the lower limit of the water level under the ecological constraints in the mine area is 4.0 m. Based on the groundwater flow field in 2016, the Yushen mining area is divided into ecologically restricted areas and unconstrained areas with a water depth of 4.0 m. Vegetation with a water depth of less than 4.0 m is highly dependent on groundwater and belongs to the ecological confinement zone. The decline of groundwater level caused by coal seam mining is very likely to cause water stress on vegetation, which is the focus of ecological environment protection in mining areas. This illuminates the limitations of ecology and water level on coal mining in Yushen mining area, which lays a theoretical foundation for further promoting water-preserved coal mining technology. [ABSTRACT FROM AUTHOR]

The stability of sandwiched water-resisting strata plays a significant role in the closed multiple-seam mining. The upper accumulated water in the upper gobs can seeped and flow into the lower mining space once the stability of sandwiched water-resisting strata is destroyed. In some situations, a sudden release of upper accumulated water is occurred, which brings serious threats for the safe mining of lower coal seam. The basic concept of water-resisting control strata under the influence of multiple mining was proposed in this paper. The damage parameter（D）calculation model of interbuRDen was established based on theories of damage mechanics. The relationships between the damage parameters（D）and the compressive strength/the damage range of interbuRDen were analyzed, respectively. Then, the influence of multiple mining damage on the stability of water-resisting control strata was investigated. The results showed that（1）The water-resisting control strata referred to the strata which did not broken under the multiple mining influences and played a significant role in preventing the downwaRD seepage and expansion of accumulated water in the upper gobs. （2）The damage parameter（D）could be used to measure the damage range of interbuRDen under multiple mining influences. （3）The relationship between the compressive strength （RD） of the interbuRDen and the damage parameter（D）was:RDof the interbuRDen showed a linear decreasing trend with the increasing of D. The reduction factor was 1-D. （4）The maximum failure depth/height(Hmax)and the maximum distance to the working face (Lmax) increased with the increase of damage parameter（D）. The larger the damage parameter（D）, the greater the increase of Hmax and Lmax. （5）The stability of water-resisting control strata was closely related with the superimposed damage induced by the multiple mining. It was necessary to comprehensively evaluate the damage range of interbuRDen under the multiple mining of upper and lower coal seams. The stability of water-resisting control strata under six different conditions were determined and the reasonable control measures were then complemented to ensure the safety of lower coal seam mining. The study on the influence of multiple mining damage on the stability of water-resisting control strata can provide a theoretical guidance for the safe mining of lower coal seam under the water accumulation area. [ABSTRACT FROM AUTHOR]

Coal mining with water protection is an inevitable choice for the sustainable development of ecologically fragile mining areas. The study and application of coal mining with water protection is an urgent problem to be solved in coal development planning, construction and production in northwest China. Taking Yushen mining area in northern Shaanxi Province as an example, this paper studies the types of water-preserved coal mining coalmines in combination with the quantity distribution of shallow water resources( water-preserved coal mining target seam) and the impact of coal mining on shallow water resources. Firstly, the spatial occurrence structure characteristics of eco-water-coal measures strata in the study area are analyzed. Also, the eco-geological environment types for the purpose of water-preserved coal mining are proposed, which are divided into oasis type with phreatic water and bottomland in desert, oasis type with surface water and valley river, loess gully type with surface runoff, and regional deep groundwater enrichment type. Secondly, the distribution of total storage per unit area of shallow water resources is calculated and determined. Then, based on the influence degree of coal mining on ecological layer and shallow water, four types of environmental engineering geological patterns( basically unaffected model, gradually restored model after destruction, gradually deteriorated model and disaster model) are proposed. Based on the analysis of the key indicators affecting the division of environmental engineering geological patterns, including the height of the water-flowing fractured zone and the mining water-resisting of residual aquiclude, etc., the zoning threshold and determination method for environmental engineering geological patterns is established. Finally, based on the distribution characteristics of shallow water resources and environmental engineering geological patterns, the grade types of water-preserved coal mining coalmines are put forward for the first time, which is divided into normal mining mine, water-preserved coal mining first-class mine, water-preserved coal mining second-class mine and water-preserved coal mining third-class mine. [ABSTRACT FROM AUTHOR]

The natural runoff condition of high intensity mining in north Shaanxi coal energy base is easy to affect ecophreatic in its adjacent regions. In this paper, aiming at the disturbance of coal resource exploitation to groundwater flow field around nature reserve, a mine field in Yushen mining area is studied. By constructing the hydrogeological model of coal-water spatial structure, the occurrence characteristics and its law of eco-phreatic in the study area are analyzed systematically. By means of physical simulation, numerical simulation and field measurement, the combined structure of coal overburden lithology, the distance between coal seam and key layer, the thickness of coal seam, the depth of coal seam, the length of coal face and so on are analyzed synthetically. The correlation analysis method is used to propose the height of the fractured zone suitable for the study area. According to the hydrogeological conditions and the mining mode of coal seam, the change of eco-phreatic flow field of Sarawusu formation after coal mining is simulated by using the method of numerical analysis of groundwater, and the characteristics of disturbance of eco-phreatic after coal seam mining are analyzed. The results show that the eco-phreatic of Sarawusu formation is developed in the whole area and its occurrence is controlled by the form of bedrock surface, and the eco-phreatic level is affected by topography, aquifer thickness, groundwater watershed and surface water. Under the influence of sedimentation, the key layer is missing in the southeastern part of the study area to form a "skylight" aqueduct. The overburden structure is mainly composed of hard-soft-hard and hard-hard-soft. The type of overburden structure plays an important role in the development height and shape of the water fractured zone. Based on the statistical analysis of the development height of several water fractured zone, it is proposed that the maximum fissure ratio is 28. 1 times in Yushen mining area, which has an important guiding significance for water-preserved mining and water hazard prevention in Yushen mining area. It is found that after coal seam mining, the loss of red soil in Baode formation in the southeast of the study area will result in the loss of eco-phreatic water and the decline of water level, with a maximum depth of 10 m. In order to protect the eco-phreatic water resources, it is suggested that when mining the coal seam of the "skylight" in the southeast part, the corresponding water-preserved mining method must be adopted. [ABSTRACT FROM AUTHOR]

Shenfu mining area is a China’s important coal production base and a typical high intensity mining field, and also a typical fragile ecological environment of arid and semi-arid areas, in which the burnt rock aquifer is one of the main groundwater resources. In order to study the influence and the protection of the burnt rock aquifer, taking the 5-2 coal mining in the first mining area of Zhangjiamao Mine field as an example, by studying the hydrogeological structure system and the water flowing fractured zone of 5-2 coal roof, this paper investigates the types and characteristics of water resources, establishes the water-preserved mining target of 5-2 coal seam, divides the water-preserved coal mining partition of 5-2 coal seam, and puts forward a new water-preserved coal mining technology which is burnt rock grouting curtain interception method. The results show that there are six main types of water resources in the study area, where only the burnt rock aquifer of 4-2 coal seam has the significance of water-preserved mining and the 5-2 coal mining area is divided into anhydrous mining area and water-preserved limited mining area of the 4-2 coal burnt rock aquifer. In the water-preserved limited mining area of 5-2 coal seam, the designed curtain wall spatial morphology, the position and quantity of curtain line and the row spacing and structure of grouting drilling are reasonable. In addition, the procedure and processes of drilling and grouting planed are scientific, and the implemented key technologies of grouting curtain, such as dual-site bidirectional water diversion grouting, zoning grouting of burnt rock full section, immediate test of anti-seepage and interception effect, are feasible. The pre-drainage of the 4-2 coal burnt rock aquifer of the working face before mining, and the measurement of the working face water inflow after mining in the water-preserved limited mining area of 5-2 coal seam show that the static reserve and the dynamic recharge of the 4-2 coal burnt rock aquifer water quantity are about 20 000 m3 and less than 5 m3 per hour respectively. It means the grouting curtain closure realizes the effective isolation of the 4-2 coal burnt rock water inside and outside the curtain, and greatly reduces the water discharge of the 4-2 coal-burnt rock water and the Changjiagou reservoir water with which it has direct hydraulic connection, and the protective mining effect of water resources is remarkable. [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 the western part of China, mine disasters such as support failure, surface stepped subsidence and mine earthquake, are prone to occur when lower coal seam is extracted which is closely beneath the coal pillars left after room-and-pillar mining with shallow overburden. In this paper, physical modelling and numerical simulation method were adopted to investigate the dynamic instability process of upper coal pillar group and the mechanism of support failure under the influence of lower coal seam mining. According to the measured statistics in some mines after coal mining of Yuyang District, only when the proportion of elastic core area of the coal pillars is greater than 31% can the room coal pillars keep long-term stability. The simulation result after mining lower coal seams shows that the failure form and instability sequence of the upper coal pillars have close relations with the positions relative to the lower coal seam working face. The damage and instability of room coal pillar occur in the positions of open-off cut, working face, and the middle of goaf successively. Furthermore, the coal pillars in the open-off cut and working face mostly show horizontal shear failure, while the coal pillars in the middle of the goaf show vertical fracturing damage. According to the numerical simulation results of Shigetai Coal Mine, the peak abutment pressure of coal pillar in upper 2-2 coal seam increases from in-situ stress 2. 8 MPa to 12 MPa after coal mining with the stress concentration factor at 4. 28. After the lower 3-1 coal seam working face mined, the peak abutment pressure of the retained pillar in upper 2-2 coal seam continually increases to 30 MPa with the stress concentration factor up to 10. 71. The open-off cut side of the lower coal seam working face showed uneven horizontally bearing with the coal pillar directly above the lower coal seam working face and the influence of horizontal tensile deformation are the main reasons for the diagonal failure mode of the boundary coal pillars. After the instability of two sides coal pillars, the roof instantaneously occur overall shear breakage, causing mine earthquake, and multi-layered strata in the roof settled suddenly in the form of "rigid body motion"and hit against the floor, leading to the collapse of the room coal pillars in the middle of goaf. At the same time, the huge impact force further leads to the full cutting of the strata between the upper and lower coal seams, which results in the roof cutting and support failure in the lower coal seam working face. It was found in the experiment that there was only about 0. 45 seconds from the failure of the first coal pillar in the overlying coal pillar group to the overall unstable movement and the final stability, among them, the full cutting of the strata between the upper and lower coal seams only took about 0. 05 seconds. [ABSTRACT FROM AUTHOR]

When using synthetic aperture radar interferometry(InSAR) technology to monitor coal mining sub-sidence, the displacement of radar line of sight(LOS) obtained is the vector superposition of three-dimensional dis-placement of surface points in vertical, north-south, east-west directions. Decomposing the LOS displacement into the surface subsidence and the horizontal displacement along the strike and incline of the working face is the basis for studying the law of mining subsidence and obtaining the parameters of surface movement. At present, the main method of inverting mining subsidence three-dimensional displacement based on InSAR LOS displacement is using three SAR images of different orbiting satellites to establish LOS displacement equations for solving three-dimensional displacement components. According to the prediction model of mining subsidence, the horizontal displacement of surface is regarded as the correlation function of subsidence, and the subsidence and horizontal displacement are calculated from a single SAR image. The LOS displacement is projected into the sub-sidence component through directly ignoring the influence of horizontal displacement. Based on the analysis of the limitations of the above methods and the basic characteristics of the surface subsidence and horizontal displacement of the near-horizontal coal seam mining on the main section of the mobile basin, the geometric equations of the multi-period InSAR LOS superposition displacement on the symmetry point of the surface moving basin was established. The equations are superimposed and differentially processed to derive the function model for LOS displacement inversion three-dimensional mining displacement. During the advancement of the working surface, because of the hysteresis of the surface movement, the center of the dynamic subsidence basin deviates to the side of the open hole. According to the characteristics of the central surface subsidence of the moving basin reaching the maximum and the horizontal displacement approaching zero, the dynamic center position of the surface moving basin is automatically searched based on the superposition and difference of the LOS displacement of adjacent pixels. Thereby, the decomposition of the dynamic three-dimensional displacement of the surface during the advancement of the working surface is realized. In this paper, the above three-dimensional displacement inversion model is implemented based on the platform of Matlab, and the model was validated by multi-phase In SAR data. The inversion results of subsidence and horizontal displacement are in a good agreement with the measured data, which is obviously superior to the method of directly decomposing surface subsidence without considering horizontal displacement. This model can be used to decompose the three-dimensional displacement monitored by InSAR in the process of surface movement stability and dynamic movement in near-horizontal coal seam mining. [ABSTRACT FROM AUTHOR]

Coal bump often occurs in the mining process between two adjacent mines under the control of large geological bodies. In order to study the coal bump mechanism between adjacent working faces of two adjacent coal mines under the condition of large fault and huge thick overburden conglomerate, this paper investigates the 23070 working face at Yuejin coal mine and the 21220 working face at Changcun coal mine in China. The analyses of monitoring data are carried out on the characteristics of coal bump behavior, microseismic spatio-temporal evolution and microseismic energy. Furthermore, the theoretical analysis and numerical simulation of stress distribution of overburden structure during the mining process of two working faces are conducted. The results show that the activation of F16 thrust fault and overall control of massive conglomerates in Yima mining area provide the stress conditions for coal bump. During the mining process of two mines’ adjacent working faces, the "asymmetric T-shaped"structure is formed between the rock beamabove the goaf and coal-rock pillar between two mines. The coal bump around the 21220 working face leads to the stress transfer onto the two mines’ pillar and the 23070 working face, which induces the coal bump around the 23070 working face. Mining disturbance between two mines leads to stress transfer and induces rock burst, which is closely related to the initial bump intensity and mining length of later working face. Finally, based on theory and engineering monitoring, a coal bump controlling technique with chain-weakening and consumption-increasing between two coal mines is put forward, which regards the weakening of the structural chain of high stress transfer as core. The results provide a theoretical basis for the study on the mechanism and control of coal bump between two adjacent working faces in two adjacent mines. [ABSTRACT FROM AUTHOR]

In order to solve the outstanding problems faced by the coal mining, the key core technologies of the future development direction and the urgent breakthrough of the coal mining are found, the domestic and foreign energy structure and the coal status are analyzed. It is pointed out that using the scientific and technological progress to realize the safe and efficient green mining and clean and efficient utilization is the development direction of the coal, and the development of intelligent coal mine is an inevitable choice for the development of the coal industry. The connotation of intelligent coal mine and three basic theoretical problems and research directions are put forward:(1) the unified expression of multi-source and heterogeneous data and the information dynamic correlation relationship in digital coalmine;(2) the mechanism of complex surrounding rock environment-mining system and the theoretical basis of intelligent control of the whole path and attitude of equipment group;(3) the system health condition prediction and maintenance decision-making mechanism of mine equipment group. Eight operational management platforms of intelligent MOS multi-system integrated management, underground robot cooperative intelligence and feed management, underground precise positioning and navigation and 5 G communication management, geological and mine mining and transportation information dynamic management, video enhancement and real-time data-driven 3 D scene reproduction remote intervention, environment and hazard perception and security early warning system management, systematic management of intelligent unmanned working face and the health management of the whole mine equipment and facilities are conceived. The functions, characteristics and key problems of each platform are analyzed, and the corresponding construction paths and methods are put forward. By analyzing the composition and construction target of intelligent coal mine, the paper puts forward eight key technology short-boards and key technologies that need to be broken in intelligent mining, and puts forward the measures to promote the development in the aspects of both technology and management. At the technical level, there are three main directions: data acquisition and utilization, intelligent decision making and equipment R & D. At the management level, scientific production capacity layout, specialized operation service and the establishment of new standard rules and regulations system are put forward. The development goal and realization path of intelligent coal mine and intelligent mining technology are pointed out. [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]

To explore the law that rotary wind from drums influences on lateral dissipation of coal dust from cutting, this paper simulated the flowing and dissipation law of wind-coal dust before and after rotary wind from drums into the face, and took the breathing zone as a height range to analyze the coal dust concentration distribution. According to the results of the study and research, a shear scrubber was developed, meanwhile, the application effect was investigated and the results of numerical simulation were verified by the measurement of coal dust concentration. Research indicates that the rotary wind from drums has a strong stability and it has very obvious entrainment to coal dust from cutting, the coal dust from TG drum enter into sidewalk by floor at the leeward 14.2 m of center of shear, the coal dust from MG drum enter into sidewalk by floor at the center of shear, soon afterwards, swarming with wide range at the leeward 2.9 m. At the breathing zone of sidewalk, the peak concentration distribution area is located in the leeward 18.3-21.8 m of center of shear, the coal dust concentration is about 300-400 mg/m3. The relative error of initial measured coal dust concentration compared with the results of numerical simulation is less than 15%. The dust-laying rate of shear scrubber is maintained at 50-80% and its average dust-laying rate is 66.9%. [ABSTRACT FROM AUTHOR]

HJC model has been widely used to describe the dynamic failure process of concrete. However,due to the reason that HJC model contains many parameters, the accurate determination on the parameters of HJC model for rock materials is a challenge. In this paper,the authors performed some laboratory experiments to determine the HJC parameters of sandstone samples that were collected from Weiyuan City,Sichuan,China. Specifically,the authors determined the elasticity modulus,Poisson's ratio,and uniaxial compressive strength of sandstone by uniaxial compression experiments, and the tensile strength by Brazilian disk splitting tests. The strength, strain rate, pressure and damage model constants were determined by fitting the HJC model to the experimental data obtained from the triaxial compression tests and uniaxial SHPB tests. The obtained HJC parameters were used to numerically simulate the SHPB tests of the sandstone samples using finite element program LS-DYNA. The results show that the stress-strain curve predicted by the HJC model is in good agreement with the experimental data. The mean error of dynamic peak stress and corresponding stain obtained by numerical simulation does not exceed 10%. This demonstrates the rationality and validity of the experimental method for determining the HJC parameters. [ABSTRACT FROM AUTHOR]

In order to study the mechanical mechanism of chamber surrounding rock in the process of excavation-supporting, the circular chamber was divided into elastic zone, plastic softening zone and plastic residual zone in accordance with mechanical characteristics of surrounding rock. The surrounding rock softening,dilatation,spatial effect and anchorage mechanical effect were considered and the softening modulus of strength parameters,coefficients of dilatancy and dilatation angle were introduced. The analytical solutions of elastoplastic stress,displacement and plastic zone radius were obtained.In addition, an example was analyzed to study the effect of different factors on the stress of plastic zone, surrounding displacement and plastic zone radius of chamber. The results show that anchorage mechanical effect can decrease plastic range and plastic zone radius for the large softening modulus of surrounding rock.While considering spatial effect when the shorter distance from excavation face to supporting face named value of x is, the bigger stress and displacement are and when value of x is greater than 10 m, the spatial effect is fail basically.Dilatancy coefficient h3 has a more important influence than h2 for surrounding displacement. Surrounding displacement of chamber under anchor bolt of different lengths can provide reference for the reserved rock deformation of supporting structure. The study in this paper can provide a theoretical basis for excavation-supporting of chamber. [ABSTRACT FROM AUTHOR]

The mechanism of force chain formation and its evolution laws in the non-continuous structure system of top coal and overlying strata are the important foundation for the calculation of support loading, the optimization of coal mining technology and the control of mine pressure. By photoelastic experiment of particles under biaxially loading and bilaterally flowing conditions, the distribution of force chains in top coal and overlying strata of fully mechanized caving mining is captured and force chain network structure is studied by topology. The study shows that the distribution of force chain in overlying strata and top coal is uniform in the initial state. After mining, the arched chain is formed near the drawing opening, and extends towards the front and upper part of the working face as the working face advances. Three main configurations of force chains in overburden strata and top-coal are identified, namely, chain, loop and chain-loop coupling respectively, which are distributed in front of the working face, undisturbed overlying strata and mining disturbed overlying strata. Besides, these configurations can be described by Betti number. Through the analysis of the distribution characteristics of the force chains in mining field, the paper reveals the forming mechanism of the supporting pressure in front of the working face and the mechanical essence of the loading action of the working face. Based on the statistical analysis of force chain strength, force chain azimuth and contact force frequency, the force chains in top coal and overlying strata display statistical features as follows; strong chain distribution of undisturbed areas in the upper overburden is relatively uniform, whereas in the mining disturbed area strong force chains develop along the arch line;In front of the working face, the vertical force chain is the majority all the time. [ABSTRACT FROM AUTHOR]

The problem of roadway support in deep coal mining or hard roof can be solved by special surrounding rock pressure release of stagger layout roadway. In this paper, the surrounding rock characteristic of gob-side roadways with or without coal pillar were analysed. Then the movement of main roof which has large impact on the stability of surrounding rock of gob-side roadway was discussed. The mechanical mechanism of pressure releasing and deformation yielding of surrounding rock structure system was studied by mechanical analysis and laboratory experiment. Results shows that the stagger layout enables roadway to be away from the stress concentration zone which transfers the pressure and avoids the problem of high ground stress. The gangue pillar structure cushions the dynamic load of falling roof and undertakes the weight of key block. The roof made up by gangue gives enough space for hard roof’ s movement which in another way protects the roadway. [ABSTRACT FROM AUTHOR]

To make it a complete system of the mechanism, prediction and control of rockburst, disturbance response instability theory is deeply studied in this paper. Control quantity, disturbance quantity and response quantity of coal rock deformation system is proposed. Rockburst is concluded as a instability phenomenon of coal rock deformed system which happens when disturbance response approaches to infinite and disturbance response instability conditions of rockburst are given,if the coal and rock deformation system is in an unsteady equilibrium state, characteristic displacement of plastic softening deformation area will increase infinitely no matter how small the disturbance increment is. The analytical solution of rockburst happens in circular roadway is derived strictly observe disturbance response instability theory, and it indicates that there are critical indexes for disturbance quantity and response quantity, the critical indexes are determined by control quantity. Monitor and control of rockburst are narrated from the angle of control quantity , disturbance quantity and response quantity. Monitoring methods such as mining stress monitoring are aimed at disturbance quantity, while monitoring methods such as drilling cuttings methods and microseismic methods are aimed at response quantity. Prevent methods such as rational mining layout, mining protective layer, rational coal pillar retention , break roof are aimed at disturbance quantity, while prevent methods such as coal seam drilling, coal seam water injection,coal seam blasting, strengthening support are aimed at disturbance quantity. [ABSTRACT FROM AUTHOR]

With the deep coal mining in China, the contradiction between the mine water inrush from aquifer underling the coal seam and the decline ecological water level is more and more serious. Based on the analysis of the assemblage characteristics between the No. 5 coal seam and the aquifer(auifuge) in Chenghe mining area, the present study is to investigate the depth of destroyed floor by combining the theoretical calculation and in-situ measurement. The influence of coal seam mining on the confined water underling the coal seam has been studied from the perspective of aquifer structure, ecological water level and water quality. The results indicate that the maximum depth of destroyed floor of the No. 5 coal seam is 8-10. 8 m, and the main control factors of the depth of destroyed floor are the dip length of working face and the lithologic association of floor. And there is a positive correlation between the dip length of working face and the depth of destroyed floor, a negative correlation between lithologic association of floor and the depth of destroyed floor. Influence degree of the aquifer structure from large to small can be divided into Ⅰ,Ⅱ,Ⅲ level area, and the Ⅰ level areas are mainly distributed in the central-south and north,which covers an area of 6. 78 km2,accounting for 45． 2% of the total area; there is no obvious effect on water level and water quality. The paper puts forward a grouting reinforcement technology to protect water resources and stabilize the ecological water level in mining, and finds an effective way for the healthy development of coal industry in Weibei region. [ABSTRACT FROM AUTHOR]

Due to the special environment of coal mine, the images are generally blurred and have weak edges, and the image super-resolution reconstruction algorithm based on dictionary learning is usually that all blocks are reconstructed by single dictionary, ignoring the differences among them and being bad for reconstructing the mine images. Combined with the characteristics of mine images, this paper proposes a multi-dictionary learning image super-resolution method with edge fusion. In the method, all image blocks are classified according to the gradient statistics and dictionary libraries are trained. Finally, the image blocks reconstructed by different dictionaries are merged into a complete high resolution image. In order to perfect the edge information, the preprocessing stage of the low-resolution image performs edge fusion to enhance their features. The high-resolution image reconstructed by dictionary learning uses the prior knowledge to fuse the edge information, thus correct the errors in the reconstruction process. The experiment shows that the effect of this method is improved compared with other super-resolution image reconstruction methods based on dictionary learning, which can reconstruct the edge details of the image well and suppress the ghosting and ringing effect, and the value of average PSNR is increased by 1. 19 dB. [ABSTRACT FROM AUTHOR]

The deep mining of coal mines leads to some significant changes in the physical properties of coal and rock, stress environment and gas occurrence law. The perturbed range of overlying rock and level of dynamic-static load have also increased significantly. In addition, the disaster effect caused by the linkage of mine groups and the control effect of large geological bodies appear in deep mining. The same disaster effect with the coexistence and conversion of rock burst and coal & gas outburst occurs. Therefore, above characteristics make the prevention and control of dynamic disaster in deep coal mines become a problem to be solved urgently. Considering the situation that the conditions of disaster breeding and mutual transformation mechanism are complex and still unclear, the quick detection method, prevention- control technology and equipment are still lacking, in this paper, the key scientific and technical problems of prevention- control for dynamic disaster in deep mining are condensed, the thought of prevention and control with different sources in multi-scales for coal and rock dynamic disasters in deep mining is proposed, the research direction of prevention and control technology for dynamic disaster in deep mining is determined, and the theory and technical framework of prevention and control with different sources in multi-scales for coal and rock dynamic disasters in deep mining are established. Based on the above achievements, the theory and technology system of prevention and control with different sources in multi-scales for coal and rock dynamic disasters in deep mining are formed successfully, which can provide a theoretical and technical support for the prevention and control of rock burst, the outburst of coal and gas or compound dynamic disaster in deep mining of coal mines in China. [ABSTRACT FROM AUTHOR]

Taking the large Changjiagou reservoir in Shenfu coal mine as an example, using hydro-geological exploration, drill hole measurement, theoretical calculation and numerical simulation, the hydrogeological conditions in the vicinity of Changjiagou reservoir were investigated. A formula of the height of water flowing fractured zone was put forward. Also, this paper studied the prevention and controlling technology of the coal seam mining for the vicinity of Changjiagou reservoir. The result shows that the height of water flowing fractured zone is about 72. 8 m, which mainly include the burnt rocks water inrush, Salawusu formation water-sand inrush, and Changjiagou reservoir water inrush. The water disaster problems surrounding Changjiagou reservoir mainly include the burnt rocks water inrush, Salawusu formation water-sand inrush, Changjiagou reservoir water inrush during mining. Based on the water inrush, the water control measures were put forward, which are coal protection pillar reserved, the curtain grouting and drainage underground, the water exploration-drainage underground combined with the drainage ground, the exploration and drainage of the goaf water overlying the coal seam, the channel cracks buried. During the 15207 working face mining, there were 28 boreholes drilled in the 4-2 coal burnt hydrothermal rock, and the curtain grouting was 625 m, the cumulative water discharge was 33 523 m3 based on coal protection pillar reserved. [ABSTRACT FROM AUTHOR]

In terms of the characteristics of stability control of hydraulic support under the condition of the fully mechanized working face with large seam dip angle, rotating, large mining height and false bow oblique, and combining with the geological and engineering conditions of fully mechanized working face numbered 12124 in Pan’er Mine, this paper studies the mechanism and method of stability control of broken roof and hydraulic support and scraper conveyor under soft coal conditions. Based on the analysis of field observation data, two instability modes including the dumping and falling of hydraulic support in fully mechanized working face with large dip angle are constructed to analyze the force characteristics of the supports by comparison. The relationships between the instability of the supports and seam dip angle, beam of support, the friction coefficient of the direct top are revealed. Then "threshold with pressure" of moving hydraulic support with pressure is derived, and the method of moving support with load, laying metal net, contacting roof and chasing coal winning machine are provided. The ratio of adjusting oblique in the rotating mining area is designed to be 1 ∶ 3 by comprehensive analysis, and the decline value of conveyor in bow pseudo-inclined mining area is determined to be less than 304 mm. With the measures of preventing sliding and falling of "three machine" which are installed jack with preventing sliding and falling, and the effective control on the "three machine" stability, wall caving and roof falling, the safety and high efficient mining of thick coal seam with large seam dip angle are realized. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of advancing speed of working face on the rockbursts in working faces by means of case studies and microseismic monitoring data analysis. Its mechanism is then revealed based on the identification of relationships between rockburst and advancing mode or speed. A dynamic control method for the advancing speed effect is presented through analyzing the microseismic characteristics of similar working faces. The results show that the rockburst hazard of working faces is associated with the advancing mode or speed. Two advancing modes, high speed and inconstant speed, tend to induce rockbursts in working faces. Advancing at a high speed can lead to the transformation of potential energy in roof strata and the release of strain energy in coal seams. Advancing at an inconstant speed can lead to the localized release of strain energy in coal seams. A dynamic method for controlling advancing speed effect is presented based on microseismic response characteristics, and its successful applications in a number of coal mines demonstrate that it can provide a guideline for the active prevention and control of rockburst hazards in deep mining. [ABSTRACT FROM AUTHOR]

In recent years, coal gangue backfill mining technology has been widely applied as one of the green mining technologies. The coal gangue filling in goaf has been in the acidic or alkaline mine water environment for a long time, its heavy metal elements in goaf have the risk of migrating to the floor and polluting groundwater. In this paper, through the static immersion test of coal gangue, the concentration of element in soaking solution was determined by ICP. The main heavy metals components in coal gangue were Be and Mn. A numerical simulation model for the migration of heavy metals in coal gangue under different floor lithology (mudstone, granite, sand-stone and limestone) was established by using COMSOL and Multiphysics. Taking Mn as an example, the diffusion distance and concentration distribution of heavy metal element in different rock floors were analyzed, and the relation between the diffusion distance of heavy metal element and the permeability coefficient of floor rock was obtained. The results show that the diffusion distance of Mn element in the bottom plate is 5. 2 m, 12. 5 m, 16 m and 19 m, respectively, when the clay cushion is not laid on the mudstone, granite, sandstone and limestone. After laying clay cushion, the diffusion distance of Mn element is 0. 9 m, 2. 8 m, 5. 2 m and 9. 1 m, and decreases by 82. 69%, 77. 60%, 67. 50%, 52. 10% respectively. [ABSTRACT FROM AUTHOR]

In order to understand the heavy metal pollution in surrounding farmland tillage soil caused by coal mine, this paper studied the area around a coal mine in southwest Shandong province. The 104 samples of surrounding farmland tillage soil were collected, and the concentration of heavy metals including Cr, Ni, Cu, Cd, Zn, Pb were tested by ICP-MS. Single factor index, nemero index and geoaccumulation index were used to analyze the spatial distribution characteristics and the appraise pollution level of six heavy metals. The results show that the six kinds of heavy metals are obviously accumulated, and have different spatial distribution characteristics in the nearby regions of coal gangue dump, industrial square, coal transfer station and transit lines. Only Cu and Ni elements have significant correlation in spatial distribution. The total pollution is in a light degree. It has no Cr element pollution, small-scale slight pollution area of Ni element, some slight pollution area and small-scale moderately pollution area of Cd element in the research area. Other elements including Cu, Zn and Pb are relatively safe. [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]

A lot of pores and fractures in some coal reservoirs are blocked by minerals or impurities, such as calcite and dolomite. The permeability of those coal seams is low. This paper puts forward a new method to increase permeability by acidification. In order to study the law of meso-structure of coal under the action of acidification, those parameters, such as specific surface area, pore volume, porosity, permeability, pore size distribution and magnetic resonance imaging, are measured by low temperature nitrogen adsorption and NMR experiments. Test results show that the coal samples' saturated water state NMR signal increases, irreducible water state NMR signal cut down, and the changes about mid-large pores peak ( T2>20 ms) is much bigger than small pores peak in T2 spectrum. The parameters that quantified by NMR, such as total porosity, effective porosity, and permeability were increased, and the residual porosity and T2 cut-off values were decreased. The specific surface area and total pore volume were increased, which quantified by the low temperature nitrogen adsorption, and the increase was mainly concentrated at the pore size of 10 nm, but the increase of high rank coal was not obvious. The nuclear magnetic resonance image directly reflects the change characteristics of the internal pore structure before and after the coal sample acidification, which provides a new way to reveal the microscopic evolution law of acidification. The comparison shows that the initial porosity of coal sample is more developed or more carbonate, silicate and other soluble minerals in the pore, the greater the change of the characteristic parameters, the better the effect of acidification. [ABSTRACT FROM AUTHOR]