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Based on the elliptic paraboloid zone theory of mining fissure, a theoretical model was established, which means that the temporal and spatial form of excellent mining gas channel was corresponding to the advancing distance of working face, and the upper and lower boundary of excellent gas channel was determined in this study. Based on the geological conditions of Qinan Coal Mine of Huaibei, this study investigated the expanding rule of mining gas channel by UDEC as well as the control action of the channel acting on the pressure relief flow under the condition of coal seam group using field test. The numerical calculations show that the typical location, height and width of excellent mining gas channel are lower with the higher drawing speed. According to the numerical calculations, the design parameters of high drilling was optimized with the higher drawing speed for the field test in 34low2 working face, which verifies the feasibility of parameters optimization for high drilling, and also confirms the guidance and control effect of drawing speed on excellent gas channel proposed in this study. [ABSTRACT FROM AUTHOR]

The fracture network of short-distance coal seams group in Liujia Coal Mine is well developed. In order to prevent water conduction caused by fracture in roof and coal seams, gas exceeding the limit in the working face that near goaf, and spontaneous combustion, based on fractal theory, Brazilian splitting test and borehole peeping statistical test, the impact of fragmentation scale and evenness of rock mass on fracture fractal characteristics were investigated. The study shows that the fractal dimension D of split fragmentation is closer to 2, the fragmentation scale becomes more even after fracture. It shows that there is a main crack that roughly divides the sample and the fissure-plane is relatively flat. The fractal dimension D of split fragmentation shows greater difference with 2, the fragmentation scale becomes more uneven and the fissure-plane is rougher. The fractal dimension D of split fragmentation and the fractal dimension D of cracks are in accordance with parabolic distribution. The fractal dimension D of split fragmentation is closer to 2, the bigger the fractal dimension D of cracks. This shows that the fragmentation scale gets more even, the less the number of cracks in the rocks, the more smooth the crack ring and the smaller the angle between the crack ring and interface of rock stratum. The fractal dimension D of split fragmentation shows greater difference with 2, the smaller the fractal dimension D of cracks. This shows that the fragmentation scale gets more uneven, the more the number of cracks in the rocks, the more rough the fissure-plane and the more irregular the crack azimuth. Crack distribution has nothing to do with the splitting fragmentation scale size, but is closely related with the homogeneity of fragmentation scale. [ABSTRACT FROM AUTHOR]

The paper discussed the dominant factor of controlling permeability, then presented the way of mining-enhanced permeability for deeper coal seam, based on the theoretical permeability model and occurrence law of crustal stress and gas pressure. From the coal unloading experiment and CT scanning in the unloading process, either the extension of original fissures occurred, or new fractures appeared, which is just the reason that the heavy decreasing of crustal stress and gas pressure makes the permeability increased hundreds or thousands times. A conceptual permeability model of unloading coal was put forward based on current theoretical models. Finally, a new theoretical model of coal permeability was built for unloading fractured coal, which brings a bridge between unloading with permeability increment. By the theoretical model, the permeability for adjacent seams could be obtained from the stress field and strain field. And the application in Haishiwan Coal Mine of Yaojie coalfield found that the theoretical model can make the gas pumping engineering scientifically and exactly in deeper coal seam. [ABSTRACT FROM AUTHOR]

In order to solve technical problems of largely deformed roadway, such as high support cost and poor support effect, a new style lengthening bolt was researched and developed. The paper studied deformation and failure feature of largely deformed roof, and analyzed force and deformation characteristic of lengthening bolt by comparison with ordinary bolt and traditional cable. Besides, the constitutive model of surrounding rock-support system was established, then, the lengthening bolt roof support system was put forward and successfully applied in 5203 ventilation roadway in Wu-jiagou Mine, which effectively control the sustainable deformation of roadway roof. The research results show that maximum elongation and breaking load of 4 m lengthening bolt respectively are 685 mm and 195 kN. Furthermore, the lengthening bolt not only gives full play to its high elongation, but ensures high support resistance. Besides, both of stability and support strength of lengthening bolt roof support system are superior than roof cable support system in late period. Field observation results show that the subsidence amount decreases more than 33% when the roof is supported by lengthening bolt roof support system, and the proportion of those lengthening bolt with 160-180 kN support strength is almost 87.5%, which achieves the goal of strong support and yield pressure. [ABSTRACT FROM AUTHOR]

To quantitalively prove the effect of temperature on RPC internal pore structure changes,the characteristics of pore structure and the fractality of RPC after high temperatures were tested by mercury intrusion porosimetry ( MIP). The development of the characteristics of pore parameters, such as the pore volume, the threshold pore size, the most probable pore size,etc.,with increasing temperature was analyzed. The volume fractal dimension of RPC in the effective region of capillary pores and transition pores were calculated. The results indicate that the pore structure degrades at high temperature, which lead to the porosity and pore volume increase with the temperature rising. The damage process of RPC can be described by means of the fractal method,at the temperature 150 °C, RPC starts to show fractal effect, the volume fractal dimension of RPC in the range of capillary pores and transition pores increase with the rising temperature. [ABSTRACT FROM AUTHOR]

Objective To develop the influenza vaccine hesitation scale for the elderly aged 60 and above and evaluate its applicability. Methods Based on the Chinese version of the parents' hesitation scale for children's influenza vaccination, combined with the characteristics of the elderly population, the influenza vaccine hesitation scale for the elderly aged 60 and above was developed, and the reliability and validity of the scale were evaluated. Results The scale finally included 3 dimensions and 14 items, the score of the total scale was 32.82 ±7.99, and the correlation coefficient between each item and the score of the total scale was between 0.20 and 0.87 (all P < 0.05). Exploratory factor analysis showed that the Kaiser -Meyer-Olkin (KMO) value of the scale was 0.916 (x²approximation = 14 315.26, P<0.05). Confirmatory factor analysis showed that the cumulative variance contribution rate of 14 common factors was 80.6%, GFI=0.909, IFI=0.961, TLI =0.952, and CFI = 0.961, indicating that the overall fitness and structural validity of the model were good. Taking whether the elderly were vaccinated with influenza vaccine or not in the influenza season in 2022, the total vaccine hesitation score and the scores of "confidences", "risk" and "support" were significantly correlated with the school standard (all P < 0.05). The Cronbach's a coefficient of the scale was 0.859, indicating that the internal consistency reliability of the scale was high. Conclusion The influenza vaccine hesitation scale for the elderly developed in this study is good in reliability, validity and applicable stability, which can be used to evaluate the hesitation level of influenza vaccine in people aged 60 and above. [ABSTRACT FROM AUTHOR]

Taking roof shallow strata as the research object, the field test research on the drilling feedback signal of variable thrust level in drilling construction process and the characteristics of drill deep-drill speed, the results showed that in drilling area drilling speed and thrust level are approximate linear positive correlation. As lithology different its drill speed growth rate is different. In blocking of the mudstone layer the drill speed is negative growth. Under 2.5-3.5 kN thrust level, the drilling speed in the coal seams, mudstone layer and sandstone layer decreases in turn. The coal seam roof of test coal mine is in the drilling area. The average drilling speed is 41. 8-43. 2 mm/s, fluctuation is -4.07% -3.01% ; The average drilling speed in sandstone is 8. 4-9. 8 mm/s, fluctuation is -16.3% -19. 0% ; The average drilling speed in mudstone is 22.4-23.5 mm/s, fluctuation is -28.1%-24.3% ;The integrity of roof mudstone is poor, there is a fissure channel in each range of 1. 1-1.3, 2.7-2.8 and 4. 1-4. 4 m, the fluctuation of drilling speed in channel is up to 122.3%; the characteristic curve of drilling depth-drilling speed can clearly characterize the location of fissure channel. [ABSTRACT FROM AUTHOR]

Coal combustion ashes, gasification ashes, and pyrolysis chars were used to simulated the residues of " three zones" from underground coal gasification, which are oxidization zone, reduction zone and dry distillation zone. The distribution characteristics of mercury, arsenic, fluorine, chromium, lead five trace elements in the leaching solution was analyzed, and compared with that in raw coal, in order to investigate their potential threat to groundwater. The results indicate that total contents of the five trace elements in the leaching solution of raw coal and the residues of "three zones" follow the order of dry distillation zone>oxidization zone>reduction zone>raw coal,within the scope of of national standard GB 20426-2006. The contents of Pb follow the order of dry distillation zone > raw coal > oxidization zone>reduction zone, they are very low and the average value of Pb is only 0. 003 0 mg/L. The contents of As follow the order of oxidization zone >>reduction zone>dry distillation zone>raw coal, and the residues in oxidization zone have the highest As leaching content of 0.1450 mg/L, almost 63 times of that in raw coal. The contents of F- follow an order of dry distillation zone>oxidization zone>reduction zone >>raw coal, and 476 times higher than that of the other four heavy metals. The leaching of Hg and Cr are not detected. [ABSTRACT FROM AUTHOR]

The sulfation reaction process and kinetics of limestone modified by wood vinegar, a kind of waste liquid, were analyzed by thermogravimetic analysis method and grain reaction model. The results show that the desulfurization performance of limestone can be effectively improved after being modified by wood vinegar in the whole temperature range (850 -1 000 °C). The phase composition analysis measured by XRD of limestone modified by wood vinegar shows that the major composition in the sample is hydration calcium acetate. The thermal decomposition of modified limestone shows the characteristic of multi-stage. The structure of thermal decomposition product of modified lime- stone, measured by scanning electron microscope and nitrogen adsorption method, is much looser than that of original limestone, which is conducive to the sulfation reaction. The rate constant of the surface reaction (k) of modified limestone is slightly smaller than original limestone's, but there is huge gap between the effective diffusivity of reactant in the product layer (Ds) of these two samples. The enhancement of sulfation is more pronounced once the product layer has been formed and consequently the promoting effect becomes greater once the sulfation reaction becomes diffusion controlled. [ABSTRACT FROM AUTHOR]

The sulfation behavior of CaO and SO2 after the carbonation/calcination cycles was evaluated in a fixed-bed and a thermogravimetic analyzer. The effects of cycle number, particle size, sulfation temperature and microstructure on sulfation conversion of CaO were investigated. The results show that the sulfation conversion of CaO decreases rapidly with the cycle number during the previous 20 cycles, and then it keeps stably with increasing the cycle number further. However, after 130 cycles, the sulfation conversion of CaO begins to increase with the number of cycles. The sulfation conversions of initial CaO, CaO after 40 cycles and 150 cycles are 0. 480,0. 207 and 0. 243 ,respectively. The particle size has the same effect on CaO sulfation conversion at the different cycles. The bigger the particle size is, the smaller the CaO sulfation conversion is. The reaction temperature between 800 and 950 t has a little effect on the sulfation conversion of initial CaO. However, the reaction temperature shows an obvious effect on the sulfation conversion of CaO with the number of cycles. Moreover, higher reaction temperature results in greater sulfation conversion of CaO with the number of cycles. [ABSTRACT FROM AUTHOR]

In order to figure out evolutionary process of roof fissure channel and spatial distribution characteristics, based on rock mechanics and gas flow variation of coal and rock stress-strain process, using deep displacement automatic monitor and fissure channel itinerant video camera, theoretrical analysis and field testing were done and the formation criterion of gas fissure channel and distribution characteristics were obtained. The results show that the coal-rock stratification becomes gas fissure channel when the transformation is smaller than lower stratification or bigger than upper stratification and the stable span must be bigger than roof exposure length, according to this, the roof shallow fissure channel of test mine is located 1.5 m and 5.0 m above the roof; with working face promoting, roof fissure channel goes through an evolutionary process; pre-existing fissures channel dominant stage and fissure channel pro-duce-expand-mature-close stage,the evolutionary cycle of fissure channel is the ratio of the distance between re-compaction area and initial stress area in front of working face and the promoting speed per day, and the evolutionary cycle of test mine is 11-14 days. [ABSTRACT FROM AUTHOR]

According to the breakage and fracture developing of overlying strata, the layer with fracture diameter of more than 10-1 mm is the mining gas channels development area. Based on the theory of voussoir beam structure, the characteristic of gas channel development in the overburden under the key stratum was studied, and the identification method of the gas pattern were established for gas flow in gas channel based on Kozeny-Carman criterion. Then the overlying rock was divided into turbulent channel area, transitional circulation channel area and seepage channel area, according to the gas pattern in gas channels, and the artificial diversion method for transitional circulation channel area was set up by taking high level suction roadway as main means. Finally, the evolution law of gas channel and its influence on gas guidance flow was inversed by field test at working face 80201 in Xinjing Coal Mine of Yangquan Coal Industry (Group) Co., Ltd., and the gas pattern was classified for transitional circulation channel area,which verified the correction and rationality of the theoretical method and the classification for mining gas channel proposed in this paper. [ABSTRACT FROM AUTHOR]

In order to quantitatively study the difference of pore connectivity and seepage capacity in coals with different coal-body structure, advanced 3D visualized model of pores for coal samples with different structure collected from Hancheng Mine, Weibei coalfield was done using a 3D-modeling technique and applying the theory of porous media 3D percolation. The spatial visualization of pores indicates that tectonic deformation has significant influence on coal pore structure. The different deformation mechanisms variously affect the porosity, pore clusters and the max pore cluster, resulting in obvious change in percolation probability. Variation of percolation probability show that pore connectivity and permeability of coals present an inverse-U-shaped relationship with the increase in tectonic deformation. The cataclastic coal has the best pore connectivity and the highest permeability, while the smallest values for these two parameters occur in mylonitic coal. The study show that brittle failure may induce the expansion of microfractures and exogenous pores, and thus results in good connectivity and high permeability. The milonitic coal has poor pore connectivity and low permeability due to the uneven distribution of pores, fractures, minerals, and maceral caused by brittle-ductile and ductile deformation effect. [ABSTRACT FROM AUTHOR]

Currently borehole extraction is a main engineering measure in coal and gas simultaneous extraction. The destruction pattern and range of drilling surrounding rock have a great influence on the link of gas channel area. In order to rationally design drilling gas guide channel for deep coal and gas simultaneous extraction and promote the guided flow, a theoretical model of drilling surrounding rock plastic zone was established. The model shows that; in deep mining environment influenced by mining unloading, a large-scale deviatoric stress area is formed in the coal and rock mass of mining space, and under the effect of high deviatoric stress, the butterfly damage zone, which is advantageous to the gas conduction, appears in the borehole surrounding rock. The butterfly zone length can reach more than dozens of times of borehole diameter. Based on the butterfly plastic zone theory, the concept of high quality gas channel was put forward, which means by coordinating mining engineering activities and gas drainage borehole layout, the gas conduction and mobile network is formed which is advantageous to the gas extraction. The construction method of high quality gas channel was determined by rationally planning working face length, mining times, mining height, and coal pillar size to form a stress environment required by the formation of high quality gas channel. Also, the drilling horizon, direction, space, setting time and other gas drainage borehole layout were determined accordingly, which was able to achieve a high efficiency, stability, long-lasting, and high quality gas channel and greatly improve the extraction efficiency. [ABSTRACT FROM AUTHOR]

The rock masses are separated by structural surfaces and there are many instability blocks with different geometric shapes which can be easily seen from the field in Anjialing open pit. It is a high risk for the slope safety due to the bad geological condition, so a study on the blocks stability is urgently needed. In this study, the step at +1300 level of the slope was investigated. Firstly, the spatial geometric parameters of the structural planes was gained by photogrammetry using a three-dimensional contact-free measuring system. Then a 3D numerical model of the structural planes was built based on the measured parameters. Finally, a self-developed software instability block fast recognition and analysis system (GeoSMA-3D) was used to search and analyze the key block of the slope rock mass. The simulation results reflect the actual situation very well, which means that the method of the key block search and analysis is reasonable and feasible. [ABSTRACT FROM AUTHOR]

Combining with an engineering case of Shirengou iron mine, mainly studied the relation between mining stress field with microseismicity and surrounding rock stability. The law of microfracture production aggregation and evolution was detailed analysed nearby No. 15 exploration line during the process of gob formation and open pit internal emission. A mechanical model was established by FEM ANSYS to simulate the mining stress field distribution under different mining conditions. Then the comparison of the stress field distribution and microseism distribution show that the rock microseismicity is induced by the change of stress status and microseism events usually aggregate in the stress concentration regions. By examining the practical field rock mass status, we find the destructiveness of the region where the high energy microseism events aggregate more serious than the surrounding area. The results show that the density and energy of microseism events can reflect destructiveness of rock mass really. It' s reasonable to take them as the rock mass stability evaluation index. At last, based on the understanding of above relationship, combing with the next stage mining stress field, the poor stability rock mass is identified and the the corresponding control measures are pointed out. [ABSTRACT FROM AUTHOR]

Aiming at the current status of coal mining problems in China, this paper put forward the concept and connotation of "scientific coal mining" and "sustainable capacity of coal mining". Scientific coal mining is to maximally obtain natural resources on the premise of the harmonized geology and ecological environment under the guidance of outlook of scientific development, and to achieve sustainable mining with safety, high efficiency, green, economy and social harmony on the premise that hazards posed by complicated geological conditions and engineering circumstances were controlled; sustainable capacity of coal mining refers to the maximal coal mining capacity using safe, high-efficient and environment-friendly method on the premise that the reserves for sustainable mining within certain period were guaranteed, mainly including three requirements; safe mining, green mining and high-efficient mining. Accordingly, innovatively proposed the assessment index system and standards of the sustainable capacity of coal mining which are comprised of mining safety level, green level and mechanization level and makes comparative analysis of the current sustainable capacities of coal mining of the five coal production areas in China, the whole China and the advanced coal mining countries in the world. The results show that the coal mining capacity in 2010 scores 42.58 on average, and the coal output which complies with the standards of the sustainable capacity of coal mining and scores over 70 is about 1.078 billion tons, accounting for only 33.27% of the overall coal output; while the sustainable capacities of coal mining of the advanced coal mining countries like the United States of America, Australia, Britain and Germany score over 90. There is still a big gap between the coal mining in China and that in the advanced coal mining countries in the world, so China should extensively disseminate the idea of scientific coal mining and sustainable capacity of coal mining, insist on scientific coal mining, and raise the scientific level of coal mining in an all-round manner. [ABSTRACT FROM AUTHOR]

Presented a study on shale gas reservoir of Longmaxi Formation of Lower Silurian in southern Sichuan Basin. The reservoir porosity was measured using nitrogen adsorption method. The pore volume, pore specific surface area and pore size distribution were studied through the isotherms and DFF analysis. Based on all of these, discussed the main factors to control the nanopore structure and the nanopore's influence on shale gas accumulation. The results show that, the pore structure of the shale gas reservoir of Longmaxi Formation is relatively complex, which is composed of nanopores and possesses a certain ruleless structure (the amorphous pore), pores are open in style and mainly consist of the cylinder pores with two ends open and parallel-plate pores with four sides open. It is concluded that openness degree of the pores improved with the increase of the vertical depth, the sizes of the main nanopores are in a range of 2 ~40 nm, which take up 88.39% of the total volume of pores and 98.85% of specific surface area. Most of the pore volume is occupied by the mesopores which are 2 ~ 50 nm in size. The micropores and mesopores of which the diameters are less than 50 nm dominate the main pore specific surface. The main internal factor to control the volume and the pore specific surface of nanopores of the shale gas reservoir in Longmaxi Formation is TOC content. It is also the important substance to provide the main storage space. The nanopores have a strong ability to absorb shale gas, the interior of which is structured filled with the shale gas, thus increase shale gas storage capacity and finally make the model characteristic complicated. The open nanopores can improve the shale gas desorbing efficiency and the permeability of the reservoirs, and then improve the shale gas production. [ABSTRACT FROM AUTHOR]

The coal bulk density significantly influences the coal dilatation during the coking process. Based on typical samples of Xinjian 1/3 and Taoshan coking coals from Qitaihe( Heilongjiang Province), the effects of bulk density on the Audibert-Arnu dilatation behavior including initial softening temperature, dilatation starting temperature, maximum dilatation and variation of Gb factor were investigated. Experimental results demonstrate that higher coal bulk density improves the initial soften temperature but decreases the dilatation starting temperature. When the bulk density is increased from 0. 88 to 1.19 t/m³, the initial soften temperature of Xinjian coal and Taoshan coal is increased by 30 and 14 °C, respectively. But the starting dilatation temperature of Xinjian coal and Taoshan coal is lowered by 19 and 15 °C, respectively. Higher bulk density clearly increases the percent dilatation and its temperature range. Gb factor of the coals is also increased with the coal bulk density. [ABSTRACT FROM AUTHOR]

On the basis of previous research of similar material, the weight ratio of iron ore powder plus barite powder to aggregates, the weight ratio of iron ore powder to iron ore powder plus barite powder, adhesive concentration and gypsum content were selected as four factors, and every factor had five variable levels. According to twenty five schemes of material mixture ratio designed by orthogonal design method, laboratory uniaxial compression test, split test and direct shear test were conducted. Physical and mechanical indexes of similar material such as unit weight, compressive strength, tensile strength, elastic modulus, poisson ratio, internal friction angle and cohesion were obtained under different material mixture ratios. The tests results show that physical and mechanical indexes of similar material vary in a large range and can meet the needs for rock similar material in different physical model test of rock slope. The sensitivity of every factor was analyzed by using extremum difference method. The results show that the weight ratio of iron ore powder plus barite powder to aggregates has control effect on density and internal friction angle of the specimen, and adhesive concentration has control effect on compressive strength, tensile strength, elastic modulus and cohesion of the specimen. The relationship between factors and parameters of similar material were studied by direct analysis charts of the factors affecting physical and mechanical indexes of the material. [ABSTRACT FROM AUTHOR]