Evaluation of the weakening behavior of gas on the coal strength and its quantitative influence on the coal deformation

The coal strength and deformation properties are key factors affecting safe coal mining and highefficiency coalbed methane(CBM)development.In this paper,reconstituted coal samples are chosen to investigate the weakening behavior of gas on coal strength,meanwhile,its effects on coal deformation are quantitatively evaluated.The results indicate that the weakening degree of gas on coal strength is closely related to the confining stress and gas pressure.Compared with non-gas-saturated coals,the maximum weakening ratios of adsorbed gas to coal strength are 10.58%,18.12%,8.55%and 14.65%under the conditions of confining stress CS=3 MPa and gas pressure GP=1 MPa,CS=3 MPa and GP=2 MPa,CS=4 MPa and GP=1 MPa,and CS=4 MPa and GP=2 MPa,respectively.Furthermore,the maximum weakening ratios of free gas to coal strength are 18.27%,36.54%,14.79%and 29.58%,respectively,under above four conditions.The maximum coal bulk strain decreases as particle sizes of coal powders increase,and it has a maximum value of 0.0227 and a minimum value of 0.0191 in particle size ranges of 0.01–0.041 and 0.5–1 mm.Under the same conditions,the coal bulk strain increases with increasing gas pressure,revealing that coal deformation properties can be enhanced by gas.

Top-coal deformation control of gob-side entry with narrow pillars and its application for fully mechanized mining face

A mechanical model to control the top-coal deformation is established in accordance with the structural characters of the gob-side entry surrounding rock for the fully-mechanic top-coal caving; the analytical solution of top coal roof-sag curve is deduced with Winkler elastic foundation beam model. By means of a calculating and analytic program, the top coal roof-sag values are calculated under the conditions of different supporting intensities, widths of narrow pillars and stiffness of top coal; meanwhile, the relationship between the roof-sag values and supporting intensity, width of narrow pillars and stiffness of top coal is analyzed as well. With the actual situation of the gob-side entry taken into consideration, the parameters of top-coal control are determined and a supporting plan is proposed for the top-coal control,which is proved to be reliable and effective by on-site verification. Some theoretical guidance and advice are put forward for the top-coal deformation control in gob-side entry for fully mechanized top-coal caving face.

Coupling mechanism between mining-induced deformation and permeability of coal

The coupling mechanism between mining-induced mechanical behavior and gas permeability of coal is effectively obtained in laboratory.This study means significant understanding of the prevention of coal-gas outburst.The testing samples of coal were drilled from the 14120 mining face at the depth of690 m.Based on the redistribution of stress during the excavation,the coupling test between mechanical state and seepage has been designed using the triaxial servo-controlled seepage equipment for thermofluid-solid coupling of coal containing methane.It is the result that there are two main factors influencing the mining-induced mechanical behavior of coal,such as the change ofσ_1-σ_3 andΔσ_1-Δσ_3.The failure mode mainly depends on the value ofσ_1-σ_3,and the peak strength value mainly depends on the value ofΔσ_1-Δσ_3.The difference of mechanical response between geostress and mining-induced stress has been obtained,which can be a theoretical support for safe mining such as reasonable gas drainage,prevention of coal-gas outburst and gas over-limit.

Experiment of dynamic property and transient magnetic effects of coal during deformation and fracture

Combining separated SHPB test device of Ф50 mm with ZDKT-type 1 transient magnetic resonance test system, long drop bar of 400 mm was used to impact coal specimens at four different speeds： 1.275, 3.287, 6.251, and 7.404 m/s. The change in waveform, the dynamic mechanical properties, and the generated effect of transient field during the coal deformation and fracture under the loads were discussed and analyzed. While magnetic signals during the coal fracture firstly needed EEMD, decomposition then had a FFT with Data Demon. The main results of the experiment are the following： the main frequency of magnetic signals was between 220 and 450 kHz and the instantaneous frequency during the damage of coal would have the instantaneous jump.

Response of Macromolecular Structure to Deformation in Tectonically Deformed Coal

The structural evolution of tectonically deformed coals （TDC） with different deformational mechanisms and different deformational intensities are investigated in depth through X-ray diffraction （XRD） analysis on 31 samples of different metamorphic grades （R ： 0.7%-3.1%） collected from the Huaibei coalfield. The results indicated that there are different evolution characteristics between the ductile and brittle deformational coals with increasing of metamorphism and deformation. On the one hand, with the increase of metamorphism, the atomic plane spacing （d002） is decreasing at step velocity, the stacking of the BSU layer （Lc） is increasing at first and then decreasing, but the extension of the BSU layer （La） and the ratio of La/Lc are decreasing initially and then increasing. On the other hand, for the brittle deformational coal, d002 is increasing initially and then decreasing, which causes an inversion of the variation of Lc and La under the lower-middle or higher-middle metamorphism grade when the deformational intensity was increasing. In contrast, in the ductile deformational coals, d002 decreased initially and then increased, and the value of L~ decreased with the increase of deformational intensity. But the value of La increased under the lower-middle metamorphism grade and increased at first and then decreased under the higher-middle metamorphism grade. We conclude that the degradation and polycondensation of TDC macromolecular structure can be obviously impacted during the ductile deformational process, because the increase and accumulation of unit dislocation perhaps transforms the stress into strain energy. Meanwhile, the brittle deformation can transform the stress into frictional heat energy, and promote the metamorphism and degradation as well. It can be concluded that deformation is more important than metamorphism to the differential evolution of the ductile and brittle deformational coals.

Theoretical analysis on the deformation characteristics of coal wall in a longwall top coal caving face

Against the background of analyzing coal wall stability in 14101 fully mechanized longwall top coal caving face in Majialiang coal mine,based on the torque equilibrium of the coal wall,shield support and the roof strata,an elastic mechanics model was established to calculate the stress applied on the coal wall.The displacement method was used to obtain the stress and deformation distributions of the coal wall.This study also researched the influence of support resistance,protective pressure to the coal wall,fracture position of the main roof and mining height on the coal wall deformation.The following conclusions are drawn:(1) The shorter the distance from the longwall face,the greater the vertical compressive stress and horizontal tensile stress borne by the coal wall.The coal wall is prone to failure in the form of compressive-shear and tension;(2) With increasing support resistance,the revolution angle of the main roof decreases linearly.As the support resistance and protective force supplied by the face guard increases,the maximum deformation of the coal wall decreases linearly;(3) As the face approaches the fracture position of the main roof,coal wall horizontal deformation increases significantly,and the coal wall is prone to instability;and(4) The best mining height of 14101 longwall face is 3.0 m.

Micro-structural evolution and their effects on physical properties in different types of tectonically deformed coals

The macromolecular structure of tectonically deformed coals(TDC)may be determined by the deformation mechanisms of coal.Alterations of the macromolecular structure change the pore structure of TDC and thereby impact physical properties such as porosity and permeability.This study focuses on structure and properties of TDC from the Huaibei and Huainan coal mining areas of southern North China.Relationships between the macromolecular structure and the pore structure of TDC were analyzed using techniques such as X-ray diffraction,high-resolution transmission electron microcopy,and the low-temperature nitrogen adsorption.The results indicated that the directional stress condition can cause the arrangement of basic structural units(BSU)more serious and closer.And,the orientation is stronger in ductile deformed coal than in brittle deformed coal.Tectonic deformation directly influences the macromolecular structure of coal and consequently results in dynamic metamorphism.Because the size of BSU in brittle deformed coal increases more slowly than in ductile deformed coal,frictional heating and stress-chemistry of shearing areas might play a more important role,locally altering coal structure under stress,in brittle deformed coal.Strain energy is more significant in increasing the ductile deformation of coal.Furthermore,mesopores account for larger percentage of the nano-scale pore volume in brittle deformed coals,while mesopores volume in ductile deformed coal diminishes rapidly along with an increase in the proportion of micropores and sub-micropores.This research also approved that the deformations of macromolecular structures change nano-scale pore structures,which are very important for gas adsorption and pervasion space for gas.Therefore,the exploration and development potential of coal bed methane is promising for reservoirs that are subjected to a certain degree of brittle deformation(such as schistose structure coal,mortar structure coal and cataclastic structure coal).It also holds promise for TDC resulting from wrinkle structure coal of low ductile deformation and later superimposed by brittle deformation.Other kinds of TDC suffering from strong brittle-ductile and ductile deformation,such as scale structure coal and mylonitic structure coal,are difficult problems to resolve.

Influence of combination forms of intact sub-layer and tectonically deformed sub-layer of coal on the gas drainage performance of boreholes: a numerical study

High concentration and large flow flux of gas drainage from underground coal seams is the precondition of reducing emission and large-scale use of gas.However,the layered occurrence of coal seams with tectonically deformed sub-layers and intact sub-layers makes it difficult to effectively drain gas through commonly designed boreholes.In this study,the gas drainage performance in coal seams with different combinations of tectonically deformed sub-layers and intact sub-layers was numerically analyzed.The analysis results show that the gas drainage curve changes from a single-stage line to a dual-stage curve as the permeability ratios of Zone II(kII)and Zone I(kI)increase,raising the difficulty in gas drainage.Furthermore,a dual-system pressure decay model based on the first-order kinetic model was developed to describe the dual-stage characteristics of pressure decay curves with different permeability ratios.In the end,the simulation results were verified with reference to in-situ drainage data from literature.The research results are helpful for mines,especially those with layered coal seams comprising tectonically deformed sub-layers and intact sub-layers,to choose appropriate gas drainage methods and develop the original drainage designs for achieving better gas drainage performance.

Tectonically deformed coal types and pore structures in Puhe and Shanchahe coal mines in western Guizhou

To evaluate the effect of tectonic deformation on coal reservoir properties, we provide an analysis of the types of tectonically deformed coal, macroand microscopic deformation and discuss pore structural characteristics and connectivity based on samples from the Puhe and Shanchahe coal mines. Our research shows that the tectonically deformed coal mostly includes cataclastic structural coal, mortar structural coal and schistose structural coal of a brittle deformation series. The major pore structures of different types of tectonically deformed coal are transitional pores and micropores. The pore volumes of macropores and visible fracture pores produced by structural deformations vary over a large range and increase with the intensity of tectonic deformation. Mesopores as connecting passages develop well in schistose structural coal. According to the shapes of intrusive mercury curves, tectonically deformed coal can be divided into parallel, open and occluded types. The parallel type has poor connectivity and is relatively closed; the open type reflects uniformly developed open pores with good connectivity while the occluded type is good for coalbed methane enrichment, but has poor connectivity between pores.

Deformed coal types and pore characteristics in Hancheng coalmines in Eastern Weibei coalfields

Based on SEM observance,the methods of low-temperature nitrogen and isothermal adsorption were used to test and analyze the coal samples of Hancheng,and pore structure characteristics of tectonic coals were discussed.The results indicate that in the same coal rank,stratification and crack are well developed in cataclastic coal,which is mostly filled by mineral substance in the geohydrologic element abundance,results in pore connectivity variation.Granulated and mylonitic coal being of these characteristics,as develop microstructures and exogenous fractures as well as large quantity of pores resulted from gas generation and strong impermeability,stimulate the recovery of seepage coal,improve coal connectivity and enhance reservoir permeability.Absorption pore(micro-pore) is dominant in coal pore for different coal body structure,the percentage of which pore aperture is from 1 to 100 nm is 71.44% to 88.15%,including large of micro-pore with the 74.56%-94.70%;with the deformation becoming more intense in the same coal rank,mesopore enlarge further,open-end pores become thin-neck-bottle-shaped pores step by step,specific surface area of micro-pore for cataclastic coal is 0.0027 m 2 /g,while mylonitic coal increases to 7.479 m 2 /g,micro-pore gradually play a dominant role in effecting pore structural parameters.

Roadway failure and support in a coal seam underlying a previously mined coal seam

The influence of an upper,mined coal seam on the stability of rock surrounding a roadway in a lower coal seam is examined.The technical problems of roadway control are discussed based on the geological conditions existing in the Liyazhuang Mine No.2 coal seam.The stress distribution and floor failure in the lower works after mining the upper coal is studied through numerical simulations.The failure mechanism of the roof and walls of a roadway located in the lower coal seam is described.The predicted deformation and failure of the roadway for different distances between the two coal seams are used to design two ways of supporting the lower structure.One is a combined support consisting of anchors with a joist steel tent and a combined anchor truss.A field test of the design was performed to good effect.The results have significance for the design of supports for roadways located in similar conditions.

Study on gob-side entry retaining in fully-mechanized longwall with top-coal caving and its application

Based on the engineering background of gob-side entry retaining in fully-mechanized longwall with top coal caving(GER-FLTC) on N2105 working face of Yuwu coal mine, by adopting the methods of theoretical analysis and numerical calculation, the control techniques of surrounding rocks in GER-FLTC working face are studied in this paper. The two main difficulties of stability of surrounding rocks at gob-side retained entry in fully-mechanized longwall working face are the stability control of top coal and control of large deformation of GER-FLTC working face. Interaction mechanical model between roofing and roadside backfilling in GER-FLTC is established and the equations for the calculation of roof-cutting resistance of roadside backfilling are derived. Results of numerical calculation show that the damage zones of top coal can be categorized into the delaminating zone of top coal above the backfilling, tensile damage zone of top coal above the retained roadway and shear damage zone of the upper rib of the solid coal. Stability control of top coal is the critical part to success of GER-FLTC. With consideration of large deformation of surrounding rocks of gob-side retained entry in fully-mechanized longwall, the support technique of‘‘roofing control and wall strengthening'' is proposed where high strength and highly prestressed anchor rods and diagonal tensile anchor cables support are used for top coal, high strength and highly prestressed yielding anchor rod support is used for solid coal and roadside prestressed load-carrying backfilling is constructed by high-water material, in order to maintain the integrity of the top coal, transfer load, high resistance yielding load-carrying of solid coal, roof-cutting of roadside backfilling and support,and to achieve GER-FLTC. Results from this study are successfully applied in engineering practice.

Geochemistry of Mercury in the Permian Tectonically Deformed Coals from Peigou Mine, Xinmi Coalfield, China

As the mercury emitted from coal combustion can lead to serious environmental issues, researchers pay more attention to the content, distribution and occurrence of mercury in coal. In this paper, the content, distribution, and occurrence of mercury in the Permian tectonically deformed coals from Peigou Mine, Xinmi coalfield, Henan Province were investigated. A total of 18 bench samples were taken from No.2-1 coals seam in Peigou Mine, including 15 coal bench samples, two roofs and one floor. The mercury concentration, mineral composition, and main inorganic element content of 18 samples were determined by DMA-80 direct mercury analyzer, XRD, and XRF respectively. The results show that the mercury content ranges from 0.047 ppm to 0.643 ppm, with an average of 0.244 ppm. Though the coal seam has turned into typical tectonically deformed coal by the strong tectonic destruction and plastic deformation, the vertical distribution of mercury has remarkable heterogeneity in coal seam section. By the analysis of correlation between mercury and the main inorganic elements and the mineral composition in coal, we infer that majority of mercury mainly relates to pyrite or kaolinite.

Geological modeling of coalbed methane reservoirs in the tectonically deformed coal seam group in the Dahebian block,western Guizhou,China

The widely spread Carboniferous-Permian coal seam group in southern China has great potential for coalbed methane resources,but the extensively developed tectonically deformed coal seriously restricts its development.Taking the Dahebian block in western Guizhou as the study area,the geological model of coalbed methane reservoirs in the tectonically deformed coal seam group was established,and the spatial distribution pattern of model parameters was clarified by clustering algorithms and factor analysis.The facies model suggests that the main coal body structures in Nos.1,4,and 7 coal seams are cataclastic coal and granulated coal,whereas the No.11 coal seam is dominated by granulated coal,which has larger thicknesses and spreads more continuously.The in situ permeability of primary undeformed coal,cataclastic coal,granulated coal,and mylonitized coal reservoirs are 0.333 mD,0.931 mD,0.146 mD,and 0.099 mD,respectively,according to the production performance analysis method.The property model constructed by facies-controlled modeling reveals that Nos.1,4,and 7 coal seams have a wider high-permeability area,but the gas content is lower;the high-permeability area in the No.11 coal seam is more limited,but the gas content is higher.The results of the self-organizing map neural network and K-means clustering indicate that the geological model can be divided into 6 clusters,the model parameter characteristics of the 6 clusters are summarized by data analysis in combination with 6 factors extracted by factor analysis,and the application of data analysis results in multi-layer coalbed methane co-development is presented.This study provides ideas for the geological modeling in the tectonically deformed coal seam group and its data analysis.

Multi-stage gas diffusion and its implications for the productivity of coalbed methane in the southern Qinshui Basin, north China

The behavior of coalbed methane(CBM)diffusion considerably influences gas productivity.Based on the multi-porous diffusion model and on-site CBM desorption data of coal cores,the behavior of CBM diffusion and its implications on the gas productivity of No.3 coal seam in the southern Qinshui Basin(SQB)were elaborately analyzed.Results indicate that CBM diffusion of No.3 coal seam demonstrates noticeable three-stage characteristics,including the fast diffusion,transitional diffusion,and slow diffusion stages.During the gas diffusion process,the gas content and/or the degree of developed pores and fractures/cleats in coal seams can affect the desorption of CBM and the amount of diffused CBM by influencing the changes in gas pressure in pores,thus controlling the behavior of gas diffusion in different stages.Because gas content and the developed degree of pores and fractures/cleats are closely associated with the deformation degree of the coal seams,variably deformed coal seams exhibit unique characteristics of gas diffusion.The low-deformation degree of the coal seams have a relatively uniform distribution of gas production over the history of a well.By contrast,the moderate-deformation degree of the coal seams have a relatively high rate and amount of gas diffusion in the fast and transitional diffusion stages,producing most of the gas in the early-to-intermediate stages of the wells.Finally,the high-deformation degree of the coal seams has a high rate and amount in the fast diffusion stage,indicating that most of the production stage occurs during the early stage of the gas production history of a well.In summary,the behavior of gas diffusion can be used for predicting gas production potential.

Spectra response from macromolecular structure evolution of tectonically deformed coal of different deformation mechanisms

Coals with different deformation mechanisms(brittle deformation,brittle-ductile deformation,and ductile deformation) repre-sent different ways in macromolecular structure evolution based on the metamorphism.The evolution of coal structure could affect the occurrence condition of coalbed methane(CBM) because the nanopore structure affected by macromolecular struc-ture is the most important reservoir for CBM.This paper analyzes the evolutions and mechanisms of structure and functional group of tectonically deformed coals(TDCs) collected from Huainan-Huaibei coalfield using X-ray diffraction(XRD),Raman spectroscopy,and Fourier Transform Infrared(FTIR) spectroscopy methods.The results show that the macromolecular struc-ture evolutions of TDC are different from the primary structure coal as a result of the different metamorphic grade and defor-mation mechanisms.The different deformation mechanisms variously affect the process of functional group and polyconden-sation of macromolecular structure.Furthermore,the tectonic deformation leads to secondary structural defects and reduces the structure stability of TDC.The coupled evolution on stacking and extension caused by the changes of secondary structural de-fects results from different deformation mechanisms.We consider that the changes of chemical structure and secondary struc-tural defects are the primary reasons for the various structure evolutions of TDC compared with primary structure coal.

Disturbance response instability theory of rock bursts in coal mines and its application

Aiming at the rock burst prevention in coal mines,this study argue that a rock burst is the instability of the coal mass deformation system with the infinite deformation response subjected to a small disturbance,and the concepts of control,disturbance and response variables of the coal mass deformation system are proposed.The analytical solution of rock bursts of circular roadways is derived,using a mechanical model of the coal mass deformation system of circular roadways,and the stress and energy conditions of the disturbance response instability of a rock burst are also presented.Based on the disturbance response instability theory,this study identifies the factors controlling the occurrence of rock bursts,involving the coal uniaxial compressive strength,coal bursting liability and roadway support stress.The relationship between the critical stress and the critical resistance zone of surrounding rock in roadways,the coal uniaxial compressive strength,roadway support stress,roadway geometric parameters and coal burst liability is revealed,and the critical stress index evaluation method of rock burst risk is proposed.Considering the disturbance and response variables of rockburst occurrence,a monitoring system of rock burst based on stress and energy monitoring is established.Considering managing the disturbance and control variables,regional and local prevention measures of rock burst are proposed from four aspects:destressing in coal mass,avoiding the mutual disturbance between multi-group mining or excavation,reducing the dynamic load disturbance and weakening of the physical properties of the coal mass.Based on the enhancement principle of the roadway support stress on the critical load of rockburst occurrence and the energy absorption effect of the support,an energy absorption and anti-bursting support technology for roadways are proposed.The disturbance response instability theory of rock bursts has formed a technical system from the aspects of mechanism,prediction and prevention to guide the engineering practice for rock burst mitigation.

A New Parameter as an Indicator of the Degree of Deformation of Coals

The deformation of coal is effected by thermal effect, pressures and tectonic stress, and the tectonic stress is the principal influence factor. However, the proposition of a useful quantitative index that responds to the degree of deformation of coals quantitatively or semi-quantitatively has been a long-debated issue. The vitrinite reflectance ellipsoid, that is, the reflectance indication surface（RIS） ellipsoid is considered to be a strain ellipsoid that reflects the sum of the strain increment caused by stress in the process of coalification. It has been used to describe the degree of deformation of the coal, but the effect of the anisotropy on the RIS ellipsoid has not yet been considered with regards to non-structural factors. In this paper, Wei＇s parameter（ε） is proposed to express the deformation degree of the strain ellipsoid based on considering the combined influence of thermal effect, pressure and tectonic stress. The equation is as follows： ε=√[（ε_1-ε_0）~2＋（ε_2-ε_0）~2＋（ε_3-ε_0）~2]/3, where ε_1=lnR_（max）, ε_2=lnR_（int）, ε_3=lnR_（min）, and ε_0=（ε_1＋ε_2＋ε_3）/3. Wei＇s parameter represents the distance from the surface to the spindle of the RIS logarithm ellipsoid; thus, the degree of deformation of the strain ellipsoid is indicated quantitatively. The formula itself, meanwhile, represents the absolute value of the degree of relative deformation and is consequently suitable for any type of deformation of the strain ellipsoid. Wei＇s parameter makes it possible to compare degrees of deformation among different deformation types of the strain ellipsoid. This equation has been tested in four types of coal： highly metamorphic but weakly deformed coal of the southern Qinshui Basin, highly metamorphic and strongly deformed coal from the Tianhushan coal mining area of Fujian, and medium metamorphic and weakly or strongly deformed coal from the Huaibei Coalfield. The results of Wei＇s parameters are consistent with the actual deformation degrees of the coal reservoirs determined by other methods, which supports the effectiveness of this method. In addition, Wei＇s parameter is an important complement to the indicators of the degrees of deformation of coals, which possess certain theoretical significance and practical values.

Structure and coalbed methane occurrence in tectonically deformed coals

Research on structure of tectonically deformed coals(TDC) is a key issue in coal and gas outburst prevention and coalbed methane(CBM) exploitation.This paper presents a summary on the research progress in TDC's structural-genetic classification,tectonic strain influence on coal microstructure,coal porosity system,coal chemical structure and constituents,and their relationship with the excess coalbed methane.Previous studies suggested that tectonic deformation had significant influence on coal microstructure,coal super microstructure,and even chemical macromolecular structure.The main mechanisms of coal deformation are the tectonic stress degradation and polycondensation metamorphism(dynamical metamorphism).Besides,under different deformation mechanisms,the ultra-and micro-structure and chemical constituents of TDC presented distinct characteristics.Based on these achievements,we propose one possible evolutionary trend of TDC with different deformation mechanisms,and suggest that the coal and gas outburst in the TDC,especially in the mylonitic coals,may be not only controlled by geological structure,but also influenced by the tectonic stress degradation of ductile deformation.Therefore,further study on TDC should be focused on the controlling mechanism of deformation on structure and composition of coal,generation conditions and occurrence state of excess coalbed methane from deformation mechanism of coal.

Structural Controls on Coalbed Methane Reservoirs in Faer Coal Mine, Southwest China

Guizhou （贵州） Province, Southwest China, is rich in coalbed methane （CBM） resources, wherein its geological structure is complicated. We discuss the occurrence characteristics of CBM based on CBM borehole test data and geological setting. In combination with the analysis of the regional tectonics, macro-and micro-scopic geological structures and pore size distributions, the structural controls on CBM reservoirs were further discussed from the aspects involving tectonic evolution, structural features, and deformation of coal. The results show that the CBM enrichment was mainly controlled by the regional tectonic subsidence and weak structural deformation on coal reservoirs after coal formation. The Yangmeishu （杨梅树） syncline and topography are the main controlling factors to the current distribution pattern of CBM, which is higher in the north than the south and trending toward the NE direction. Normal faults and fractures can be divided into open, closed, and occluded types. The open type reduces both gas content and methane concentration of nearby coal seams. The closed type causes the decrease of gas content, while methane concentration is still high. The occluded type fail to reduces gas content, and even results in the enrichment of CBM in small areas near fault. Moderate brittle deformation can improve the pore structure and development of structural fracture of coal reservoir.Cataclastic structural coals with well-developed fractures and relatively uniformly distributed pore structures are common in the Faer （发耳） coal mine, which are favorable for the production of CBM.