The development of the Paleogene coal seams in China's offshore basin areas generally had the characteristics of coal measures with large thicknesses,large numbers of coal seams,thin single coal seams,poor stabili...The development of the Paleogene coal seams in China's offshore basin areas generally had the characteristics of coal measures with large thicknesses,large numbers of coal seams,thin single coal seams,poor stability,scattered vertical distribution,and a wide distribution range.This study selected the Enping Formation of the ZhuⅠDepression in the northern section of the South China Sea as an example to determine the macro-control factors of the development of the Paleogene coal seam groups.An analysis was carried out on the influencing effects and patterns of the astronomical cycles related to the development of the thin coal seam groups in the region.A floating astronomical time scale of the Enping Formation was established,and the sedimentary time limit of the Enping Formation was determined to be approximately 6.15 Ma±.In addition,the cyclostratigraphy analysis results of the natural gamma-ray data of Well XJ in the Enping Formation of the Xijiang Sag revealed that the development of the thin coal seams had probably been affected by short eccentricity and precession factors.The formation process of coal seams was determined to have been affected by high seasonal contrast,precipitation,and insolation.During the periods with high values of short eccentricity,the seasonal contrasts tended to be high.During those periods,fluctuations in the precession controls resulted in periodic volume changes in precipitation and insolation of the region,resulting in the development of thin coal seams.It was also found that the periods with low precession were the most conducive to coal seam development.On that basis,combined with such factors as sedimentary environmental conditions conducive to the development of thin coal seam groups,this study established a theoretical model of the comprehensive influences of short eccentricity and precession on the development and distribution of Paleogene thin coal seam groups in offshore lacustrine basins.The patterns of the Paleogene astronomical periods and paleoclimate evolution,along with the control factors which impacted the development of thin coal seam groups in offshore lacustrine basins,were revealed.展开更多
Coalbed methane(CBM)is a significant factor in triggering coal and gas outburst disaster,while also serving as a clean fuel.With the increasing depth of mining operations,coal seams that exhibit high levels of gas con...Coalbed methane(CBM)is a significant factor in triggering coal and gas outburst disaster,while also serving as a clean fuel.With the increasing depth of mining operations,coal seams that exhibit high levels of gas content and low permeability have become increasingly prevalent.While controllable shockwave(CSW)technology has proven effective in enhancing CBM in laboratory settings,there is a lack of reports on its field applications in soft and low-permeability coal seams.This study establishes the governing equations for stress waves induced by CSW.Laplace numerical inversion was employed to analyse the dynamic response of the coal seam during CSW antireflection.Additionally,quantitative calculations were performed for the crushed zone,fracture zone,and effective CSW influence range,which guided the selection of field test parameters.The results of the field test unveiled a substantial improvement in the gas permeability coefficient,the average rate of pure methane flowrate,and the mean gas flowrate within a 10 m radius of the antireflection borehole.These enhancements were notable,showing increases of 3 times,13.72 times,and 11.48 times,respectively.Furthermore,the field test performed on the CSW antireflection gas extraction hole cluster demonstrated a noticeable improvement in CBM extraction.After antireflection,the maximum peak gas concentration and maximum peak pure methane flow reached 71.2%and 2.59 m^(3)/min,respectively.These findings will offer valuable guidance for the application of CSW antireflection technology in soft and low-permeability coal seams.展开更多
Indirect fracturing in the roof of broken soft coal seams has been demonstrated to be a feasible technology.In this work,the No.5 coal seam in the Hancheng block was taken as the research object.Based on the findings ...Indirect fracturing in the roof of broken soft coal seams has been demonstrated to be a feasible technology.In this work,the No.5 coal seam in the Hancheng block was taken as the research object.Based on the findings of true triaxial hydraulic fracturing experiments and field pilot under this technology and the cohesive element method,a 3D numerical model of indirect fracturing in the roof of broken soft coal seams was established,the fracture morphology propagation and evolution law under different conditions was investigated,and analysis of main controlling factors of fracture parameters was conducted with the combination weight method,which was based on grey incidence,analytic hierarchy process and entropy weight method.The results show that“士”-shaped fractures,T-shaped fractures,cross fractures,H-shaped fractures,and“干”-shaped fractures dominated by horizontal fractures were formed.Different parameter combinations can form different fracture morphologies.When the coal seam permeability is lower and the minimum horizontal principal stress difference between layers and fracturing fluid injection rate are both larger,it tends to form“士”-shaped fractures.When the coal seam permeability and minimum horizontal principal stress between layers and perforation position are moderate,cross fractures are easily generated.Different fracture parameters have different main controlling factors.Engineering factors of perforation location,fracturing fluid injection rate and viscosity are the dominant factors of hydraulic fracture shape parameters.This study can provide a reference for the design of indirect fracturing in the roof of broken soft coal seams.展开更多
We applied the reflectivity method and the constrained sparse spike inverse modeling(CSSI) method to the interpretation of coal field lithologic seismic data.After introducing the principles of these two methods we di...We applied the reflectivity method and the constrained sparse spike inverse modeling(CSSI) method to the interpretation of coal field lithologic seismic data.After introducing the principles of these two methods we discuss some parameters of a geological model involving possible gas enriched areas or intruded igneous rock.The geological model was constructed and a 60 Hz seismic response profile was obtained looking for igneous rock intrusion and coked areas of the coal seam using the reflectivity method.Starting from synthesized logging data from two wells and a synthesized seismic wavelet we calibrated the model to show accurate strata.Finally,we predicted the lithology within a 10 m igneous rock area,a 3 m coal seam area,and a coked area using the CSSI technique.The results show that the CSSI technique can identify hard to recognize lithologic features that normal profil-ing methods might miss.It can quantitatively analyze and evaluate the intrusive area,the coked area,and the gas-enriched area.展开更多
Numerical simulations and field tests were used to investigate the changes in ground stress and deformation of, and gas flow from, a protected coal seam under which an extra-thin coal seam was drilled. The geological ...Numerical simulations and field tests were used to investigate the changes in ground stress and deformation of, and gas flow from, a protected coal seam under which an extra-thin coal seam was drilled. The geological conditions were: 0.5 meter mining height, 18.5 meter coal seam spacing and a hard limestone/fine sandstone inter-stratum. For these conditions we conclude: 1) the overlying coal-rock mass bends and sinks without the appearance of a caving zone, and 2) the protected coal seam is in the bending zone and undergoes expansion deformation in the stress-relaxed area. The deformation was 12 mm and the relative defor- mation was 0.15%. As mining proceeds, deformation in the protected layer begins as compression, then becomes a rapid expansion and, finally, reaches a stable value. A large number of bed separation crannies are created in the stress-relaxed area and the permeability coefficient of the coal seam was increased 403 fold. Grid penetration boreholes were evenly drilled toward the protected coal seam to affect pressure relief and gas drainage. This made the gas pressure decrease from 0.75 to 0.15 MPa, the gas content decrease from 13 to 4.66 m3/t and the gas drainage reach 64%.展开更多
Analyzed the situations and characteristics of thin coal seam mining and its mining technologies,and introduced the mining innovation technology used by Tianchen Coal Mine of Zhaozhuang Coal Company of China.This inno...Analyzed the situations and characteristics of thin coal seam mining and its mining technologies,and introduced the mining innovation technology used by Tianchen Coal Mine of Zhaozhuang Coal Company of China.This innovation technology combined the fully mechanized mining with individual props,and the working face of mining is over length,irregular form and double units.The rotational adjusting mining technology on thin coal seam is also practiced in this new mining technology.The detail technologies,such as outlays of working face and ways,mining methods,equipments of cutting,transporting and sporting,have been introduced.So that,using the synthetic and creative mining tech- nologies,Tianchen Coal Mine solves the mining problems of thin coal seam successfully.展开更多
The relationship between support and surrounding rock is of great significance to the control of surrounding rock in mining process.In view of the fact that most of the existing numerical simulation methods construct ...The relationship between support and surrounding rock is of great significance to the control of surrounding rock in mining process.In view of the fact that most of the existing numerical simulation methods construct virtual elements and stress servo control to approximately replace the hydraulic support problem,this paper establishes a new numerical model of hydraulic support with the same working characteristics as the actual hydraulic support by integrating numerical simulation software Rhino,Griddle and FLAC3D,which can realize the simulation of different working conditions.Based on this model,the influence mechanism of the supporting strength of hydraulic support on surrounding rock stress regulation and coal stability in front of the top coal caving face in extra thick coal seam were researched.Firstly,under different support intensity,the abutment pressure of the bearing coal and the coal in front of it presents the “three-stage”evolution characteristics.The influence range of support intensity is 15%–30%.Secondly,1.5 MPa is the upper limit of impact that the support strength can have on the front coal failure area.Thirdly,within a displacement range of 2.76 m from the coal wall,a support strength of1.5 MPa provides optimal control of the horizontal displacement of the coal.展开更多
Injecting carbon dioxide(CO_(2))into coal seams may unlock substantial carbon sequestration potential.Since the coal acts like a carbon filter,it can preferentially absorb significant amounts of CO_(2).To explore this...Injecting carbon dioxide(CO_(2))into coal seams may unlock substantial carbon sequestration potential.Since the coal acts like a carbon filter,it can preferentially absorb significant amounts of CO_(2).To explore this further,desorption of the adsorbed gas due to pressure drop is investigated in this paper,to achieve an improved understanding of the long-term fate of injected CO_(2) during post-injection period.This paper presents a dual porosity model coupling gas flow,adsorption and geomechanics for studying coupled processes and effectiveness of CO_(2) sequestration in coals.A new adsorption?desorption model derived based on thermodynamics is incorporated,particularly,the desorption hysteresis is considered.The reliability of the proposed adsorption-desorption isotherm is examined via validation tests.It is indicated that occurrence of desorption hysteresis is attributed to the adsorption-induced pore deformation.After injection ceases,the injected gas continues to propagate further from the injection well,while the pressure in the vicinity of the injection well experiences a significant drop.Although the adsorbed gas near the well also decreases,this decrease is less compared to that in pressure because of desorption hysteresis.The unceasing spread of CO_(2) and drops of pressure and adsorbed gas depend on the degree of desorption hysteresis and heterogeneity of coals,which should be considered when designing CO_(2) sequestration into coal seams.展开更多
In recent years,the mining depth of steeply inclined coal seams in the Urumqi mining area has gradually increased.Local deformation of mining coal-rock results in frequent rockbursts.This has become a critical issue t...In recent years,the mining depth of steeply inclined coal seams in the Urumqi mining area has gradually increased.Local deformation of mining coal-rock results in frequent rockbursts.This has become a critical issue that affects the safe mining of deep,steeply inclined coal seams.In this work,we adopt a perspective centered on localized deformation in coal-rock mining and systematically combine theoretical analyses and extensive data mining of voluminous microseismic data.We describe a mechanical model for the urgently inclined mining of both the sandwiched rock pillar and the roof,explaining the mechanical response behavior of key disaster-prone zones within the deep working face,affected by the dynamics of deep mining.By exploring the spatial correlation inherent in extensive microseismic data,we delineate the“time-space”response relationship that governs the dynamic failure of coal-rock during the progression of the sharply inclined working face.The results disclose that(1)the distinctive coal-rock occurrence structure characterized by a“sandwiched rock pillar-B6 roof”constitutes the origin of rockburst in the southern mining area of the Wudong Coal Mine,with both elements presenting different degrees of deformation localization with increasing mining depth.(2)As mining depth increases,the bending deformation and energy accumulation within the rock pillar and roof show nonlinear acceleration.The localized deformation of deep,steeply inclined coal-rock engenders the spatial superposition of squeezing and prying effects in both the strike and dip directions,increasing the energy distribution disparity and stress asymmetry of the“sandwiched rock pillar-B3+6 coal seam-B6 roof”configuration.This makes worse the propensity for frequent dynamic disasters in the working face.(3)The developed high-energy distortion zone“inner-outer”control technology effectively reduces high stress concentration and energy distortion in the surrounding rock.After implementation,the average apparent resistivity in the rock pillar and B6 roof substantially increased by 430%and 300%,respectively,thus guaranteeing the safe and efficient development of steeply inclined coal seams.展开更多
In order to clarify the danger of water breakout in the bottom plate of extra-thick coal seam mining, 2202 working face of a mine in the west is taken as the research object, and it is proposed to use the on-site moni...In order to clarify the danger of water breakout in the bottom plate of extra-thick coal seam mining, 2202 working face of a mine in the west is taken as the research object, and it is proposed to use the on-site monitoring means combining borehole peeping and microseismic monitoring, combined with the theoretical analysis to analyze the danger of water breakout in the bottom plate. The results show that: 1) the theoretically calculated maximum damage depth of the bottom plate is 27.5 m, and its layer is located above the Austrian ash aquifer, which has the danger of water breakout;2) the drill hole peeping at the bottom plate of the working face shows that the depth of the bottom plate fissure development reaches 26 m, and the integrity of the water barrier layer has been damaged, so there is the risk of water breakout;3) for the microseismic monitoring of the anomalous area, the bottom plate of the return air downstream channel occurs in the field with a one-week lag, which shows that microseismic monitoring events may reflect the water breakout of the underground. This shows that the microseismic monitoring events can reflect the changes of the underground flow field, which can provide a reference basis for the early warning of water breakout. The research results can provide reference for the prediction of sudden water hazard.展开更多
This research proposes the utilization of a geopolymer-based blasting sealing material to improve the profitability of coal sales and reduce the rate of coal fragmentation during blasting in open pit mines.The study f...This research proposes the utilization of a geopolymer-based blasting sealing material to improve the profitability of coal sales and reduce the rate of coal fragmentation during blasting in open pit mines.The study first focused on optimizing the strength of the sealant material and reducing curing time.This was achieved by regulating the slag doping and sodium silicate solution modulus.The findings demonstrated that increasing slag content and improving the material resulted in an early rise in strength while increasing the modulus of the sodium silicate solution extended the curing time.The slag doping level was fixed at 80 g,and the sodium silicate solution modulus was set at 1.5.To achieve a strength of 3.12 MPa,the water/gel ratio was set at 0.5.The initial setting time was determined to be 33 min,meeting the required field test duration.Secondly,the strength requirements for field implementation were assessed by simulating the action time and force destruction process of the sealing material during blasting using ANSYS/LS-DYNA software.The results indicated that the modified material meets these requirements.Finally,the Shengli Open Pit Coal Mine served as the site for the field test.It was observed that the hole-sealing material’s hydration reaction created a laminated and flocculated gel inside it.This enhanced the density of the modified material.Additionally,the pregelatinized starch,functioning as an organic binder,filled the gaps between the gels,enhancing the cohesion and bonding coefficient of the material.Upon analyzing the post-blasting shooting effect diagram using the Split-Desktop software,it was determined that the utilization of the modified blast hole plugging material resulted in a decrease in the rate of coal fragmentation from 33.2%to 21.1%.This reduction exhibited a minimal error of 1.63%when compared to the field measurement,thereby providing further confirmation of the exceptional plugging capabilities of the modified material.This study significantly contributes to establishing a solid theoretical basis for enhancing the blasting efficiency of open pit mines and,in turn,enhancing their economic advantages.展开更多
The gas content is crucial for evaluating coal and gas outburst potential in underground coal mining. This study focuses on investigating the in-situ coal seam gas content and gas sorption capacity in a representative...The gas content is crucial for evaluating coal and gas outburst potential in underground coal mining. This study focuses on investigating the in-situ coal seam gas content and gas sorption capacity in a representative coal seam with multiple sections (A1, A2, and A3) in the Sydney basin, where the CO_(2) composition exceeds 90%. The fast direct desorption method and associated devices were described in detail and employed to measure the in-situ gas components (Q_(1), Q_(2), and Q_(3)) of the coal seam. The results show that in-situ total gas content (Q_(T)) ranges from 9.48 m^(3)/t for the A2 section to 14.80 m^(3)/t for the A3 section, surpassing the Level 2 outburst threshold limit value, thereby necessitating gas drainage measures. Among the gas components, Q_(2) demonstrates the highest contribution to Q_(T), ranging between 55% and 70%. Furthermore, high-pressure isothermal gas sorption experiments were conducted on coal samples from each seam section to explore their gas sorption capacity. The Langmuir model accurately characterizes CO_(2) sorption behavior, with ft coefcients (R^(2)) greater than 0.99. Strong positive correlations are observed between in-situ gas content and Langmuir volume, as well as between residual gas content (Q_(3)) and sorption hysteresis. Notably, the A3 seam section is proved to have a higher outburst propensity due to its higher Q_(1) and Q_(2) gas contents, lower sorption hysteresis, and reduced coal toughness f value. The insights derived from the study can contribute to the development of efective gas management strategies and enhance the safety and efciency of coal mining operations.展开更多
A comprehensive study was undertaken at Jiaozi coal mine to investigate the development regularity of ground fissures in shallow buried coal seam mining with Karst landform,shedding light on the development type,geogr...A comprehensive study was undertaken at Jiaozi coal mine to investigate the development regularity of ground fissures in shallow buried coal seam mining with Karst landform,shedding light on the development type,geographical distribution,dynamic development process,and failure mechanism of these ground fissures by employing field monitoring,numerical simulation,and theoretical analysis.The findings demonstrate that ground fissure development has an obvious feature of subregion,and its geographical distribution is significantly affected by topography.Tensile type,open type,and stepped type are three different categories of ground fissure.Ground fissures emerge dynamically as the panel advances,and they typically develop with a distance of less than periodic weighting step distance in advance of panel advancing position.Ground fissures present the dynamic development feature,temporary fissure has the ability of self-healing.The dynamic development process of ground fissure with closed-distance coal seam repeated mining is expounded,and the development scale is a dynamic development stage of“closure→expansion→stabilized”on the basis of the original development scale.From the perspective of topsoil deformation,the computation model considering two points movement vectors towards two directions of the gob and the ground surface is established,the development criterion considering the critical deformation value of topsoil is obtained.The mechanical model of hinged structure of inclined body is proposed to clarify the ground fissure development,and the interaction between slope activity and ground fissure development is expounded.These research results fulfill the gap of ground fissures about development regularity and formation mechanism,and can contribute to ground fissure prevention and treatment with Karst landform.展开更多
A number of rockburst accidents occurring in soft coal seams have shown that the rockburst mechanism involved in soft coal seams is significantly different from that involved in hard coal seams. Therefore, the method ...A number of rockburst accidents occurring in soft coal seams have shown that the rockburst mechanism involved in soft coal seams is significantly different from that involved in hard coal seams. Therefore, the method used to evaluate rockburst in hard coal seams is not applicable to soft coal seams. This paper established an energy integral model for the rockburst-inducing area and a friction work calculation model for the plastic area. If the remaining energy after the coal seam is broken in the rockburstinducing area is greater than the friction work required for the coal to burst out, then a rockburst accident will occur. Mechanisms of ‘‘quaking without bursting" and ‘‘quaking and bursting" are clarified for soft coal seams and corresponding control measures are proposed as the optimization of roadway layouts and use of ‘‘three strong systems"(strong de-stressing, strong supporting, and strong monitoring).展开更多
Cable truss systems have been widely applied in roadways with complicated conditions, such as the large cross-sections of deep wells, and high tectonic stress. However, they are rarely applied to roadways with extreme...Cable truss systems have been widely applied in roadways with complicated conditions, such as the large cross-sections of deep wells, and high tectonic stress. However, they are rarely applied to roadways with extremely thick coal seams because the control mechanism of the system for the deformation of the roof and the separation between coal rock segments is not completely understood. By using the relationship between the support system and the roof strata, a mechanical model was established to calculate the deformation of the roof in a thick coal seam with bedding separation under different support conditions: with an anchor truss support and without support. On this basis, the research was used to deduce a method for computing the minimum pre-tightening forces in the anchor truss, the maximum amounts of subsidence and separation with, and without, anchor truss support under the roof, and the maximum subsidence and the decreasing amounts of the separation before and after adopting the anchor truss. Additionally, mechanical relationships between the minimum pre-tightening force and the anchoring force in the anchor were analyzed. By taking a typical roadway with thick coal roof as an example, the theoretical results mentioned above were applied in the analysis and testing of a roof supporting project in a roadway field to verify the accuracy of the theory: favorable experimental results were achieved. In addition, the relationships among other parameters were analyzed, including the minimum pre-tightening forces applied by the anchor truss, the angle of inclination of the anchor cable, and the array pitch. Meanwhile, the changing characteristics of the amounts of roof separation and subsidence with key parameters of the support system(such as array pitch, pre-tightening force, and inclination angle) were also analyzed. The research results revealed the acting mechanism of the anchor truss in control of roadway stability with a thick coal seam, providing a theoretical basis of its application in coal mining.展开更多
The behavior of gob-side entry under dynamic pressure is totally different from the one driven after the movement of overlying strata above the adjacent coalface goal. The gob-side entry will experience severe roof la...The behavior of gob-side entry under dynamic pressure is totally different from the one driven after the movement of overlying strata above the adjacent coalface goal. The gob-side entry will experience severe roof lateral structural adjustments caused by adjacent coalface mining. Thus the deformation and failure characteristics of narrow coal pillar along the gob should be carefully considered. On the basis of the data of the gob-side entry obtained in a thin coal seam under dynamic pressure, the measures to reinforce the narrow coal pillar are put forward. In addition, the non-harmonious controlling of the rock structures and non-equilibrium gob-side entry deformation is proposed to avoid potential failure. Field practices show that the supporting problems of the gob-side entry under dynamic pressure can be well addressed, which could be used in other similar minin~ cases.展开更多
When an extremely thick rock bed exists above a protected coal seam in the bending zone given the condition of a min- ing protective seam, this extremely thick rock bed controls the movement of the entire overlying st...When an extremely thick rock bed exists above a protected coal seam in the bending zone given the condition of a min- ing protective seam, this extremely thick rock bed controls the movement of the entire overlying stratum. This extremely thick rock bed, called a "main key stratum", will not subside nor break for a long time, causing lower fractures and bed separations not to close and gas can migrate to the bed separation areas along the fractures. These bed separations become gas enrichment areas. By analyzing the rule of fracture evolution and gas migration under the main key stratum after the deep protective coal seam has been mined, we propose a new gas drainage method which uses bore holes, drilled through rock and coal seams at great depths for draining pressure relief gas. In this method, the bores are located at a high level suction roadway (we can also drill them in the drill- ing field located high in an air gateway). Given the practice in the Haizi mine, the gas drainage rate can reach 73% in the middle coal group, with a gas drainage radius over 100m.展开更多
The paper presents the mining method for the close quarter coal seams with thin rock sheet, that is mining the low coal seam, recovering the top coal seam after putting down the roof rock of the low coal seam. Practic...The paper presents the mining method for the close quarter coal seams with thin rock sheet, that is mining the low coal seam, recovering the top coal seam after putting down the roof rock of the low coal seam. Practice has proved that in recovering the top coal outside the face width after the rock between seams falls naturally or is demolished, the technology is simple, easy to operate and does not make a great demand for technical equipment. In the process of recovering the top coal, the low seam support could not be affected seriously, and two seams mining could be coordinated. Compared with the individual mining method, this mining method can produce a better economic benefit.展开更多
基金The Scientific Research Project under contract No.CCL2021RCPS172KQNthe Formation Mechanism and Distribution Prediction of Cenozoic Marine Source rocks in Qiongdongnan and Pearl River Mouth Basin under contract No.2021-KT-YXKY01+3 种基金the Resource Potential,Accumulation Mechanism and Breakthrough Direction of Potential Oil-rich Sags in Offshore Basins of China under contract No.2021-KT-YXKY-03the National Natural Science Foundation of China(NSFC)under contract No.42372132the Open Foundation of Hebei Provincial Key Laboratory of Resource Survey and Researchthe National Natural Science Foundation of China(NSFC)under contract Nos 42072188,42272205。
文摘The development of the Paleogene coal seams in China's offshore basin areas generally had the characteristics of coal measures with large thicknesses,large numbers of coal seams,thin single coal seams,poor stability,scattered vertical distribution,and a wide distribution range.This study selected the Enping Formation of the ZhuⅠDepression in the northern section of the South China Sea as an example to determine the macro-control factors of the development of the Paleogene coal seam groups.An analysis was carried out on the influencing effects and patterns of the astronomical cycles related to the development of the thin coal seam groups in the region.A floating astronomical time scale of the Enping Formation was established,and the sedimentary time limit of the Enping Formation was determined to be approximately 6.15 Ma±.In addition,the cyclostratigraphy analysis results of the natural gamma-ray data of Well XJ in the Enping Formation of the Xijiang Sag revealed that the development of the thin coal seams had probably been affected by short eccentricity and precession factors.The formation process of coal seams was determined to have been affected by high seasonal contrast,precipitation,and insolation.During the periods with high values of short eccentricity,the seasonal contrasts tended to be high.During those periods,fluctuations in the precession controls resulted in periodic volume changes in precipitation and insolation of the region,resulting in the development of thin coal seams.It was also found that the periods with low precession were the most conducive to coal seam development.On that basis,combined with such factors as sedimentary environmental conditions conducive to the development of thin coal seam groups,this study established a theoretical model of the comprehensive influences of short eccentricity and precession on the development and distribution of Paleogene thin coal seam groups in offshore lacustrine basins.The patterns of the Paleogene astronomical periods and paleoclimate evolution,along with the control factors which impacted the development of thin coal seam groups in offshore lacustrine basins,were revealed.
基金supported by the National Natural Science Foundation of China(52074013,52374179)China Huaneng Group Science and Technology Project(HNKJ20-H87)+1 种基金Natural Science Foundation of Anhui Province(2208085ME125)Hefei Comprehensive National Science Center(21KZS216),which are gratefully appreciated.
文摘Coalbed methane(CBM)is a significant factor in triggering coal and gas outburst disaster,while also serving as a clean fuel.With the increasing depth of mining operations,coal seams that exhibit high levels of gas content and low permeability have become increasingly prevalent.While controllable shockwave(CSW)technology has proven effective in enhancing CBM in laboratory settings,there is a lack of reports on its field applications in soft and low-permeability coal seams.This study establishes the governing equations for stress waves induced by CSW.Laplace numerical inversion was employed to analyse the dynamic response of the coal seam during CSW antireflection.Additionally,quantitative calculations were performed for the crushed zone,fracture zone,and effective CSW influence range,which guided the selection of field test parameters.The results of the field test unveiled a substantial improvement in the gas permeability coefficient,the average rate of pure methane flowrate,and the mean gas flowrate within a 10 m radius of the antireflection borehole.These enhancements were notable,showing increases of 3 times,13.72 times,and 11.48 times,respectively.Furthermore,the field test performed on the CSW antireflection gas extraction hole cluster demonstrated a noticeable improvement in CBM extraction.After antireflection,the maximum peak gas concentration and maximum peak pure methane flow reached 71.2%and 2.59 m^(3)/min,respectively.These findings will offer valuable guidance for the application of CSW antireflection technology in soft and low-permeability coal seams.
基金National Natural Science Foundation of China(11672333).
文摘Indirect fracturing in the roof of broken soft coal seams has been demonstrated to be a feasible technology.In this work,the No.5 coal seam in the Hancheng block was taken as the research object.Based on the findings of true triaxial hydraulic fracturing experiments and field pilot under this technology and the cohesive element method,a 3D numerical model of indirect fracturing in the roof of broken soft coal seams was established,the fracture morphology propagation and evolution law under different conditions was investigated,and analysis of main controlling factors of fracture parameters was conducted with the combination weight method,which was based on grey incidence,analytic hierarchy process and entropy weight method.The results show that“士”-shaped fractures,T-shaped fractures,cross fractures,H-shaped fractures,and“干”-shaped fractures dominated by horizontal fractures were formed.Different parameter combinations can form different fracture morphologies.When the coal seam permeability is lower and the minimum horizontal principal stress difference between layers and fracturing fluid injection rate are both larger,it tends to form“士”-shaped fractures.When the coal seam permeability and minimum horizontal principal stress between layers and perforation position are moderate,cross fractures are easily generated.Different fracture parameters have different main controlling factors.Engineering factors of perforation location,fracturing fluid injection rate and viscosity are the dominant factors of hydraulic fracture shape parameters.This study can provide a reference for the design of indirect fracturing in the roof of broken soft coal seams.
基金Projects 40874054 and 40804026 supported by the National Natural Science Foundation of Chinathe National Basic Research Program of China (2007CB209400 and 2009CB219603)the National Key Scientific and Technological Project (2008ZX05035)
文摘We applied the reflectivity method and the constrained sparse spike inverse modeling(CSSI) method to the interpretation of coal field lithologic seismic data.After introducing the principles of these two methods we discuss some parameters of a geological model involving possible gas enriched areas or intruded igneous rock.The geological model was constructed and a 60 Hz seismic response profile was obtained looking for igneous rock intrusion and coked areas of the coal seam using the reflectivity method.Starting from synthesized logging data from two wells and a synthesized seismic wavelet we calibrated the model to show accurate strata.Finally,we predicted the lithology within a 10 m igneous rock area,a 3 m coal seam area,and a coked area using the CSSI technique.The results show that the CSSI technique can identify hard to recognize lithologic features that normal profil-ing methods might miss.It can quantitatively analyze and evaluate the intrusive area,the coked area,and the gas-enriched area.
基金Projects 2005CB221503 supported by the National Basic Research Program of China70533050 and 50674089 by the National Natural Science Foundation of China2005BA813B-3-06 by the National Tenth Five-Year Key Scientific and Technological Project
文摘Numerical simulations and field tests were used to investigate the changes in ground stress and deformation of, and gas flow from, a protected coal seam under which an extra-thin coal seam was drilled. The geological conditions were: 0.5 meter mining height, 18.5 meter coal seam spacing and a hard limestone/fine sandstone inter-stratum. For these conditions we conclude: 1) the overlying coal-rock mass bends and sinks without the appearance of a caving zone, and 2) the protected coal seam is in the bending zone and undergoes expansion deformation in the stress-relaxed area. The deformation was 12 mm and the relative defor- mation was 0.15%. As mining proceeds, deformation in the protected layer begins as compression, then becomes a rapid expansion and, finally, reaches a stable value. A large number of bed separation crannies are created in the stress-relaxed area and the permeability coefficient of the coal seam was increased 403 fold. Grid penetration boreholes were evenly drilled toward the protected coal seam to affect pressure relief and gas drainage. This made the gas pressure decrease from 0.75 to 0.15 MPa, the gas content decrease from 13 to 4.66 m3/t and the gas drainage reach 64%.
基金Supported by the National Natural Science Foundation of China (50375026, 50375028) the National High-tech R&D Program of China (863 Program) (2012AA06A407)
基金the Natural Science Fund of China(70771060)the Production Safety and Supervision of Management Bureau of China(04-116)+3 种基金the National Soft Science Planed Program(2004DGQ3D090)and(2006GXQ3D154)the Natural Science Fund of Shandong Province(Y2006H10)the Social Science Planning Program of Shandong Province(06BJJ005)the Soft-science Planed Program of Shandong Province(2007RKA134)
文摘Analyzed the situations and characteristics of thin coal seam mining and its mining technologies,and introduced the mining innovation technology used by Tianchen Coal Mine of Zhaozhuang Coal Company of China.This innovation technology combined the fully mechanized mining with individual props,and the working face of mining is over length,irregular form and double units.The rotational adjusting mining technology on thin coal seam is also practiced in this new mining technology.The detail technologies,such as outlays of working face and ways,mining methods,equipments of cutting,transporting and sporting,have been introduced.So that,using the synthetic and creative mining tech- nologies,Tianchen Coal Mine solves the mining problems of thin coal seam successfully.
基金supported by Distinguished Youth Funds of National Natural Science Foundation of China (No.51925402)National Natural Science Foundation of China (Nos.51904203 and 52174125)+4 种基金the China Postdoctoral Science Foundation (No.2021M702049)the Tencent Foundation or XPLORER PRIZEShanxi Science and Technology Major Project Funds (No.20201102004)Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering (No.2021SX-TD001)Open Fund Research Project Supported by State Key Laboratory of Strata Intelligent Control and Green Mining Co-founded by Shandong Province and the Ministry of Science and Technology (No.SICGM202209)。
文摘The relationship between support and surrounding rock is of great significance to the control of surrounding rock in mining process.In view of the fact that most of the existing numerical simulation methods construct virtual elements and stress servo control to approximately replace the hydraulic support problem,this paper establishes a new numerical model of hydraulic support with the same working characteristics as the actual hydraulic support by integrating numerical simulation software Rhino,Griddle and FLAC3D,which can realize the simulation of different working conditions.Based on this model,the influence mechanism of the supporting strength of hydraulic support on surrounding rock stress regulation and coal stability in front of the top coal caving face in extra thick coal seam were researched.Firstly,under different support intensity,the abutment pressure of the bearing coal and the coal in front of it presents the “three-stage”evolution characteristics.The influence range of support intensity is 15%–30%.Secondly,1.5 MPa is the upper limit of impact that the support strength can have on the front coal failure area.Thirdly,within a displacement range of 2.76 m from the coal wall,a support strength of1.5 MPa provides optimal control of the horizontal displacement of the coal.
基金The research was conducted as part of the“Establishing a Research Observatory to Unlock European Coal Seams for CO_(2) Storage(ROCCS)”project(Grant No.899336)The work of the second author is also sponsored by Shanghai Pujiang Program(Grant No.23PJ1412600)。
文摘Injecting carbon dioxide(CO_(2))into coal seams may unlock substantial carbon sequestration potential.Since the coal acts like a carbon filter,it can preferentially absorb significant amounts of CO_(2).To explore this further,desorption of the adsorbed gas due to pressure drop is investigated in this paper,to achieve an improved understanding of the long-term fate of injected CO_(2) during post-injection period.This paper presents a dual porosity model coupling gas flow,adsorption and geomechanics for studying coupled processes and effectiveness of CO_(2) sequestration in coals.A new adsorption?desorption model derived based on thermodynamics is incorporated,particularly,the desorption hysteresis is considered.The reliability of the proposed adsorption-desorption isotherm is examined via validation tests.It is indicated that occurrence of desorption hysteresis is attributed to the adsorption-induced pore deformation.After injection ceases,the injected gas continues to propagate further from the injection well,while the pressure in the vicinity of the injection well experiences a significant drop.Although the adsorbed gas near the well also decreases,this decrease is less compared to that in pressure because of desorption hysteresis.The unceasing spread of CO_(2) and drops of pressure and adsorbed gas depend on the degree of desorption hysteresis and heterogeneity of coals,which should be considered when designing CO_(2) sequestration into coal seams.
基金financially supported by the Major Program of the National Natural Science Foundation of China(No.52394191)the Outstanding Ph.D Dissertation Cultivating Program of Xi’an University of Science and Technology(No.PY22001)the National Foundation for studying abroad(No.[2022]87)。
文摘In recent years,the mining depth of steeply inclined coal seams in the Urumqi mining area has gradually increased.Local deformation of mining coal-rock results in frequent rockbursts.This has become a critical issue that affects the safe mining of deep,steeply inclined coal seams.In this work,we adopt a perspective centered on localized deformation in coal-rock mining and systematically combine theoretical analyses and extensive data mining of voluminous microseismic data.We describe a mechanical model for the urgently inclined mining of both the sandwiched rock pillar and the roof,explaining the mechanical response behavior of key disaster-prone zones within the deep working face,affected by the dynamics of deep mining.By exploring the spatial correlation inherent in extensive microseismic data,we delineate the“time-space”response relationship that governs the dynamic failure of coal-rock during the progression of the sharply inclined working face.The results disclose that(1)the distinctive coal-rock occurrence structure characterized by a“sandwiched rock pillar-B6 roof”constitutes the origin of rockburst in the southern mining area of the Wudong Coal Mine,with both elements presenting different degrees of deformation localization with increasing mining depth.(2)As mining depth increases,the bending deformation and energy accumulation within the rock pillar and roof show nonlinear acceleration.The localized deformation of deep,steeply inclined coal-rock engenders the spatial superposition of squeezing and prying effects in both the strike and dip directions,increasing the energy distribution disparity and stress asymmetry of the“sandwiched rock pillar-B3+6 coal seam-B6 roof”configuration.This makes worse the propensity for frequent dynamic disasters in the working face.(3)The developed high-energy distortion zone“inner-outer”control technology effectively reduces high stress concentration and energy distortion in the surrounding rock.After implementation,the average apparent resistivity in the rock pillar and B6 roof substantially increased by 430%and 300%,respectively,thus guaranteeing the safe and efficient development of steeply inclined coal seams.
文摘In order to clarify the danger of water breakout in the bottom plate of extra-thick coal seam mining, 2202 working face of a mine in the west is taken as the research object, and it is proposed to use the on-site monitoring means combining borehole peeping and microseismic monitoring, combined with the theoretical analysis to analyze the danger of water breakout in the bottom plate. The results show that: 1) the theoretically calculated maximum damage depth of the bottom plate is 27.5 m, and its layer is located above the Austrian ash aquifer, which has the danger of water breakout;2) the drill hole peeping at the bottom plate of the working face shows that the depth of the bottom plate fissure development reaches 26 m, and the integrity of the water barrier layer has been damaged, so there is the risk of water breakout;3) for the microseismic monitoring of the anomalous area, the bottom plate of the return air downstream channel occurs in the field with a one-week lag, which shows that microseismic monitoring events may reflect the water breakout of the underground. This shows that the microseismic monitoring events can reflect the changes of the underground flow field, which can provide a reference basis for the early warning of water breakout. The research results can provide reference for the prediction of sudden water hazard.
基金financially supported by the National Natural Science Foundation of China (No. 52174131)
文摘This research proposes the utilization of a geopolymer-based blasting sealing material to improve the profitability of coal sales and reduce the rate of coal fragmentation during blasting in open pit mines.The study first focused on optimizing the strength of the sealant material and reducing curing time.This was achieved by regulating the slag doping and sodium silicate solution modulus.The findings demonstrated that increasing slag content and improving the material resulted in an early rise in strength while increasing the modulus of the sodium silicate solution extended the curing time.The slag doping level was fixed at 80 g,and the sodium silicate solution modulus was set at 1.5.To achieve a strength of 3.12 MPa,the water/gel ratio was set at 0.5.The initial setting time was determined to be 33 min,meeting the required field test duration.Secondly,the strength requirements for field implementation were assessed by simulating the action time and force destruction process of the sealing material during blasting using ANSYS/LS-DYNA software.The results indicated that the modified material meets these requirements.Finally,the Shengli Open Pit Coal Mine served as the site for the field test.It was observed that the hole-sealing material’s hydration reaction created a laminated and flocculated gel inside it.This enhanced the density of the modified material.Additionally,the pregelatinized starch,functioning as an organic binder,filled the gaps between the gels,enhancing the cohesion and bonding coefficient of the material.Upon analyzing the post-blasting shooting effect diagram using the Split-Desktop software,it was determined that the utilization of the modified blast hole plugging material resulted in a decrease in the rate of coal fragmentation from 33.2%to 21.1%.This reduction exhibited a minimal error of 1.63%when compared to the field measurement,thereby providing further confirmation of the exceptional plugging capabilities of the modified material.This study significantly contributes to establishing a solid theoretical basis for enhancing the blasting efficiency of open pit mines and,in turn,enhancing their economic advantages.
基金supported by China Scholarship Council(202006430006)the International Postgraduate Tuition Award(IPTA)of the University of Wollongongthe research funding provided by the Mine A,ACARP Project C35015 and Coal Services Health and Safety Trust.
文摘The gas content is crucial for evaluating coal and gas outburst potential in underground coal mining. This study focuses on investigating the in-situ coal seam gas content and gas sorption capacity in a representative coal seam with multiple sections (A1, A2, and A3) in the Sydney basin, where the CO_(2) composition exceeds 90%. The fast direct desorption method and associated devices were described in detail and employed to measure the in-situ gas components (Q_(1), Q_(2), and Q_(3)) of the coal seam. The results show that in-situ total gas content (Q_(T)) ranges from 9.48 m^(3)/t for the A2 section to 14.80 m^(3)/t for the A3 section, surpassing the Level 2 outburst threshold limit value, thereby necessitating gas drainage measures. Among the gas components, Q_(2) demonstrates the highest contribution to Q_(T), ranging between 55% and 70%. Furthermore, high-pressure isothermal gas sorption experiments were conducted on coal samples from each seam section to explore their gas sorption capacity. The Langmuir model accurately characterizes CO_(2) sorption behavior, with ft coefcients (R^(2)) greater than 0.99. Strong positive correlations are observed between in-situ gas content and Langmuir volume, as well as between residual gas content (Q_(3)) and sorption hysteresis. Notably, the A3 seam section is proved to have a higher outburst propensity due to its higher Q_(1) and Q_(2) gas contents, lower sorption hysteresis, and reduced coal toughness f value. The insights derived from the study can contribute to the development of efective gas management strategies and enhance the safety and efciency of coal mining operations.
基金funded by State Key Laboratory of Strata Intelligent Control and Green Mining Cofounded by Shandong Province and the Ministry of Science and Technology,Shandong University of Science and Technology(Grant No.MDPC2023ZR01)Open Fund of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining(Grant No.WPUKFJJ2019-19)Major research project of Guizhou Provincial Department of Education on innovative groups(Grant No.Qianjiaohe KY[2019]070)。
文摘A comprehensive study was undertaken at Jiaozi coal mine to investigate the development regularity of ground fissures in shallow buried coal seam mining with Karst landform,shedding light on the development type,geographical distribution,dynamic development process,and failure mechanism of these ground fissures by employing field monitoring,numerical simulation,and theoretical analysis.The findings demonstrate that ground fissure development has an obvious feature of subregion,and its geographical distribution is significantly affected by topography.Tensile type,open type,and stepped type are three different categories of ground fissure.Ground fissures emerge dynamically as the panel advances,and they typically develop with a distance of less than periodic weighting step distance in advance of panel advancing position.Ground fissures present the dynamic development feature,temporary fissure has the ability of self-healing.The dynamic development process of ground fissure with closed-distance coal seam repeated mining is expounded,and the development scale is a dynamic development stage of“closure→expansion→stabilized”on the basis of the original development scale.From the perspective of topsoil deformation,the computation model considering two points movement vectors towards two directions of the gob and the ground surface is established,the development criterion considering the critical deformation value of topsoil is obtained.The mechanical model of hinged structure of inclined body is proposed to clarify the ground fissure development,and the interaction between slope activity and ground fissure development is expounded.These research results fulfill the gap of ground fissures about development regularity and formation mechanism,and can contribute to ground fissure prevention and treatment with Karst landform.
基金Financial supports for this work by the National Program on Key Basic Research Project (No.210CB226800)the National Natural Science Foundation of China (Nos.51274022 and 51174016)
文摘A number of rockburst accidents occurring in soft coal seams have shown that the rockburst mechanism involved in soft coal seams is significantly different from that involved in hard coal seams. Therefore, the method used to evaluate rockburst in hard coal seams is not applicable to soft coal seams. This paper established an energy integral model for the rockburst-inducing area and a friction work calculation model for the plastic area. If the remaining energy after the coal seam is broken in the rockburstinducing area is greater than the friction work required for the coal to burst out, then a rockburst accident will occur. Mechanisms of ‘‘quaking without bursting" and ‘‘quaking and bursting" are clarified for soft coal seams and corresponding control measures are proposed as the optimization of roadway layouts and use of ‘‘three strong systems"(strong de-stressing, strong supporting, and strong monitoring).
基金Project(51404248)supported by the National Natural Science Foundation of the Youth Science Foundation of ChinaProject(2017XKQY012)supported by Fundamental Research Funds for the Central Universities of ChinaProject(2014M551702)supported by the China Postdoctoral Science Foundation
文摘Cable truss systems have been widely applied in roadways with complicated conditions, such as the large cross-sections of deep wells, and high tectonic stress. However, they are rarely applied to roadways with extremely thick coal seams because the control mechanism of the system for the deformation of the roof and the separation between coal rock segments is not completely understood. By using the relationship between the support system and the roof strata, a mechanical model was established to calculate the deformation of the roof in a thick coal seam with bedding separation under different support conditions: with an anchor truss support and without support. On this basis, the research was used to deduce a method for computing the minimum pre-tightening forces in the anchor truss, the maximum amounts of subsidence and separation with, and without, anchor truss support under the roof, and the maximum subsidence and the decreasing amounts of the separation before and after adopting the anchor truss. Additionally, mechanical relationships between the minimum pre-tightening force and the anchoring force in the anchor were analyzed. By taking a typical roadway with thick coal roof as an example, the theoretical results mentioned above were applied in the analysis and testing of a roof supporting project in a roadway field to verify the accuracy of the theory: favorable experimental results were achieved. In addition, the relationships among other parameters were analyzed, including the minimum pre-tightening forces applied by the anchor truss, the angle of inclination of the anchor cable, and the array pitch. Meanwhile, the changing characteristics of the amounts of roof separation and subsidence with key parameters of the support system(such as array pitch, pre-tightening force, and inclination angle) were also analyzed. The research results revealed the acting mechanism of the anchor truss in control of roadway stability with a thick coal seam, providing a theoretical basis of its application in coal mining.
基金supported by the National Natural Science Foundation of China (Grant No.51104093)
文摘The behavior of gob-side entry under dynamic pressure is totally different from the one driven after the movement of overlying strata above the adjacent coalface goal. The gob-side entry will experience severe roof lateral structural adjustments caused by adjacent coalface mining. Thus the deformation and failure characteristics of narrow coal pillar along the gob should be carefully considered. On the basis of the data of the gob-side entry obtained in a thin coal seam under dynamic pressure, the measures to reinforce the narrow coal pillar are put forward. In addition, the non-harmonious controlling of the rock structures and non-equilibrium gob-side entry deformation is proposed to avoid potential failure. Field practices show that the supporting problems of the gob-side entry under dynamic pressure can be well addressed, which could be used in other similar minin~ cases.
基金Projects 2005CB221503 supported by the National Basic Research Program of China70533050 and 50674089 by the National Natural Science Foundation of China2005BA813B-3-06 by the National Tenth 5-Year Key Scientific and Technological Project
文摘When an extremely thick rock bed exists above a protected coal seam in the bending zone given the condition of a min- ing protective seam, this extremely thick rock bed controls the movement of the entire overlying stratum. This extremely thick rock bed, called a "main key stratum", will not subside nor break for a long time, causing lower fractures and bed separations not to close and gas can migrate to the bed separation areas along the fractures. These bed separations become gas enrichment areas. By analyzing the rule of fracture evolution and gas migration under the main key stratum after the deep protective coal seam has been mined, we propose a new gas drainage method which uses bore holes, drilled through rock and coal seams at great depths for draining pressure relief gas. In this method, the bores are located at a high level suction roadway (we can also drill them in the drill- ing field located high in an air gateway). Given the practice in the Haizi mine, the gas drainage rate can reach 73% in the middle coal group, with a gas drainage radius over 100m.
文摘The paper presents the mining method for the close quarter coal seams with thin rock sheet, that is mining the low coal seam, recovering the top coal seam after putting down the roof rock of the low coal seam. Practice has proved that in recovering the top coal outside the face width after the rock between seams falls naturally or is demolished, the technology is simple, easy to operate and does not make a great demand for technical equipment. In the process of recovering the top coal, the low seam support could not be affected seriously, and two seams mining could be coordinated. Compared with the individual mining method, this mining method can produce a better economic benefit.