Fire extinguishing mechanism and application research of nitrogen injection displacement

Guoshu Zhang

Key Laboratory of Coal Mine Safety and Efficient Exploitation of Ministry of Education;

Anhui University of Science and Technology, Huainan, Anhui Province, China

Shujie Yuan

Key Laboratory of Integrated Coal Exploitation and Gas Extraction, Anhui

University of Science and Technology, Huainan, Anhui Province, China

Ming Deng

Anhui University of Science & Technology, Huainan, Anhui Province, China

ABSTRACT: Spontaneous combustion in sealed goaf has characteristics such as large scope, uncertain fire source and difficult extinguishment. Based on the analysis of disadvantages of traditional method of nitrogen injection for fire-prevention, a new fire-extinguishing technology, nitrogen injection displacement, was presented. The mechanism of nitrogen injection displacement, factors influencing effectiveness of fire extinguishing, system design and key technology were studied. The technology was successfully applied in longwall 1115(3) of Zhangji Coal Mine, Huainan.

KEYWORDS: Mine fire, nitrogen injection displacement, fire extinguishing

 

 

Study on characteristics and control technology of mining induced stress shell in thick coal seam

Guangxiang Xie

Key Laboratory of Coal Mine Safety and Efficient Exploitation of Ministry of Education;

Anhui University of Science and Technology, Huainan, Anhui Province, China

Key Laboratory of Integrated Coal Exploitation and Gas Extraction, Anhui University of Science

and Technology, Huainan, Anhui Province, China

Ke Yang

Key Laboratory of Integrated Coal Exploitation and Gas Extraction, Anhui University of Science

and Technology, Huainan, Anhui Province, China

ABSTRACT: In order to understand and master distributing and evolving patterns of stress induced by mining profoundly, and to control and utilize the action of rock pressure effectively, according to the geological and technological conditions of thick coal seam with fully mechanized top-coal caving (FMTC) of Huainan and Huaibei coal mines, in-situ observation, numerical and physical modeling tests has been carried investigate into the distribution patterns of stress field in surrounding rock of fully mechanized top-coal caving (FMTC) face in the large-scale and three-dimensional space. The results showed that a macro stress shell composed of high stress exists in surrounding rock of an FMTC face. The mining induced stress shell (MISS), which bears and transfers the loads of overlying strata, acts as the primary supporting system of forces, and is the corpus of characterizing three-dimensional and macro rock pressure distribution of mining face. Its external and internal shape changes with the variations in the working face structure as the face advances. Some factors affecting on MISS development have been synthetically considered and analyzed, which including mining-height, persevered pillar width, advancing rate, mining method and parameters. And their acting mechanisms and mechanical effects are opened up. The results based on discovery and analysis of MISS and its’ development mechanism affected by geological and mining parameters are of guiding significance for engineering practice, i.e. control and utilization of rock pressure, design and choice of supports, supporting design and dynamic maintenance of gates, precaution of rock burst, gas drainage and safety monitoring etc.

KEYWORDS: Mining induced stress shell, fully mechanized top-coal caving, ground control, advancing velocity, pillar width

 

 

Thermal hazard in Chinese coal mines and measures of its control

Shujie Yuan

Key Laboratory of Integrated Coal Exploitation and Gas Extraction, Anhui University of Science and Technology, Huainan, Anhui Province, China

Key Laboratory of Coal Mine Safety and Efficient Exploitation of Ministry of Education, Huainan, Anhui Province, China

Zhenbin Zhang, Kai Deng, Chaomei Li

School of Energy and Safety, Anhui University of Science and Technology, Huainan, Anhui Province, China

ABSTRACT: With increase of mining depth of coal mines in China, thermal hazard problem in mines is getting more and more serious, affecting safety and productivity. In the paper thermal hazard situation in Chinese coal mines was presented, including geographical distribution of high-temperature mines, and diseases caused by high temperature. The reasons of thermal hazard formation and its influencing factors were analyzed. The fact was pointed out, that in deep mines heat release of rocks is the major reason of high temperature. Thermal conditions standards in mines of China and main countermeasures of high-temperature control were presented.

KEYWORDS: Mine disasters, thermal hazard, air conditioning

 

 

Research on surrounding rock control techniques of the second gob-side entry retaining for Y-type ventilation

Xinzhu Hua

Laboratory of Coal Mine Safety and Efficient Exploitation of Ministry of Education;

Anhui University of Science and Technology, Huainan, Anhui Province, China

Yingfu Li, Denglong Zhang

Anhui University of Science and Technology, Huainan, Anhui Province, China

ABSTRACT: Traditional U-type ventilation is difficult to better dilute gushing gas from the upper-corner of goaf, which causes gas accumulation in the upper-corner. Y-type ventilation can change the direction of air flow, so it is able to change the laws of gas movement in the goaf, and if supplemented by other measures to control gas, the problem of gas accumulation and gas over-flow can be fundamentally solved in the upper-corner of high gas coal face. Taking No.512(5) working face of Xieyi mine in Huainan as project background, it is analyzed that the purpose of the second gob-side entry retaining and deformation characteristics of surrounding rock in different periods, and some suggestions are offered to control surrounding rock deformation of the second gob-side entry retaining. The industrial experiments show that the technique of the second gob-side entry retaining achieves good results in No.512(5) working face of Xieyi mine.

KEYWORDS: Y-type ventilation, the second gob-side entry retaining, surrounding rock control technique

 

 

Numerical modeling of outbursts of coal and gas with a coupled simulator

Sheng Xue

Key Laboratory of Coal Production and Methane Extraction, Anhui University of Science

and Technology, Huainan, Anhui Province, China

CSIRO Earth Science and Resource Engineering, Pullenvale, QLD, Australia

Y.C. Wang, X. Xie

CSIRO Earth Science and Resource Engineering, Pullenvale, QLD, Australia

ABSTRACT: An outburst of coal and gas is a major hazard in underground coal mining. It occurs when certain conditions of coal and rock stress, coal strength and gassiness in coal are met. A three-dimensional mechanical and fluid coupled numerical simulator, SimBurst, has been developed to simulate the process of the outburst. This paper describes the fundamentals of the simulator and the results of investigations on the effects of key coal seam and mining parameters on the initiation of the outburst, in particular the effects on gas content threshold values – a key index used to predict the occurrence of the outburst in Australia and China. The simulated results show that some parameters such as mining depth, coal strength, permeability and gas de-sorption/adsorption characteristics have significant effects on the threshold values, indicating that it is inappropriate to use the same gas content threshold value for outburst prediction in different underground coal mines, rather the value should be set according to the specific coal seam and mining parameters of each mine or mining panel.

KEYWORDS: Outburst, numerical modeling, SimBurst, gas content

 

 

The influence of sealing abandoned areas on climatic conditions in the room and pillar extraction method in copper mining

Stanisław Nawrat

AGH University of Science and Technology, Krakow, Poland

K. Soroko, S. Gola

KGHM Polska Miedź S.A., Lubin, Poland

ABSTRACT: In Polish copper mines ore extraction is carried out at depths of between 600 and 1200 m. Both depth and approved mining methods cause gradual deterioration of climatic conditions in the underground excavations. The assurance of further mining requires using appropriate prophylactic methods, such as: increasing of air stream volume in mining areas, suitable regulation of air flow and use of air cooling. This article demonstrates the changes of climatic conditions in the mining excavations and dependence on resistance of ventilation dams which are used in sealing abandoned area in the room and pillar method of copper ore deposit extrac-tion.

 

 

Proecological technology utilization of methane from mines

Piotr Czaja, Stanisław Nawrat, Sebastian Napieraj

AGH University of Science and Technology, Krakow, Poland

ABSTRACT: Coal production is accompanied by the release of methane, which for security reasons is removed from the mine. Annually in Poland into the atmosphere with ventilation air is emitted around 580 million m3 of methane. Methane is a greenhouse gas which has a potential 21 times greater than carbon dioxide. The maximum content of methane in ventilation air according to the Polish mining law amounts to 0.75%. The use of methane from ventilation air is very important from economic and environmental reasons. Efficient way to use low concentration air-methane mixtures is catalytic oxidation.

 

 

Numerical simulation of airflow in blind headings ventilated with freestanding fans

Marian Branny, Bernard Nowak

AGH University of Science and Technology, Krakow, Poland

ABSTRACT: Room and pillar headings are frequently ventilated with the use of freestanding fans. The range of penetration of an air stream generated by jet fan is determined by several parameters among them the major are initial parameters of stream and the place of fan’s installation. In the paper are presented airflow patterns inside a heading which are involved by jet fans. The fans are placed in different positions at the entrance section of heading. A series of numerical tests was performed to determine the effect of different fan’s positions on airflow and efficiency of headings ventilation. Three viscosity models of turbulence were used in calculations, mainly two equations model k-ε and k-ω SST and one equation of Spalart-Allmaras. Results were compared with some mine measurements.

KEYWORDS: Auxiliary systems, jet fans, CFD simulation

 

 

Mining in Poland – history and future

Antoni Tajduś, Piotr Czaja, Marek Cała

AGH University of Science and Technology, Krakow, Poland

ABSTRACT: Poland is one of the countries rich in various minerals. There are significant deposits of hard coal and brown coal, copper ore, zinc and lead ore, rock salt, native sulphur, gypsum, kaolin, rock minerals, remedial and geothermal waters, as well as some deposits of natural gas and small volume of oil. The paper discusses in more detail the volumes of the resources, the problems related to their extraction and the perspectives of several of the most important Polish mine plants, that is: hard and brown coal, copper ore, zinc and lead ore, sulphur, natural gas and oil.

KEYWORDS: mining, exploitation, material resources, power safety

 

 

The influence of natural hazards on occupational safety in Polish collieries

Zbigniew Burtan

AGH University of Science and Technology, Krakow, Poland

ABSTRACT: The coal mining sector in Poland is exceptional throughout the world in that underground mining operations are accompanied by nearly all natural hazards while the scale and intensity of their occurrence is constantly growing. That applies mostly to dangers associated with methane emissions, tendency of self-ignition of coal, seismic activity of the rock strata and climatic conditions.

This study briefly describes the coal deposits in Poland, highlighting the aspects that may lead to intensification of natural hazards and help predict their scale and tendency. The paper attempts an analysis of technological factors that might further enhance the methane-related hazards, fires and coal bumps, particularly in the context of monitoring and control methods. The analysis clearly identifies the need for safety precautions and preventive measures to be put in place in Polish collieries.

 

 

Three-dimensional numerical simulation of spontaneous combustion in goaf of fully mechanized top-coal caving longwall

Weimin Cheng, Gang Wang, Jiacai Zhang, Lulu Sun

University of Science and Technology, Qingdao, Shandong Province, China

Gang Wang, Jun Xie

Commonwealth Scientific and Industrial Research Organization, Brisbane, Australia

ABSTRACT: In the fully-mechanized mining top-coal caving face spontaneous combustion accident, high temperature ignition sources are mostly away from the floor at a certain height over the spatial position, rather than the position of the flat floor currently considered. The spontaneous combustion in the three-dimensional goaf was studied. By using CFD software – Fluent, it establishes the spontaneous combustion three-dimensional mathematical model of the loosen coal in the goaf, and simulates the spontaneous combustion process in the model. The simulation results show that along the height direction of goaf, from the floor up, the oxygen concentration decreases progressively. The distribution of low oxygen concentration is just like an “O” district, while the distribution of high is just like a “U” zone. In the rear of the fully-mechanized mining top-coal caving face goaf, the spontaneous combustion not only exists along the strike direction but also in the vertical direction. The intersecting area in both directions constitutes the actual spatial spontaneous combustion “three zones” of the goaf.

KEYWORDS: Goaf, three-dimensional space, spontaneous combustion, numerical simulation

 

 

The stability of soft rock roadway supporting and the analysis of fractal feature of surrounding rock crack

Xiangdong Zhang, Mingxing Zhang, Jianlai Xu

Liaoning Technical University, Fuxin, Liaoning Province, China

ABSTRACT: The rock burst is one of the major problems in deep mining. How to predict the rock burst effectively and to reduce the disaster caused by the rock burst, has great significance. The rock burst is affected by many complex factors, so the forecast of rock burst intensity is a nonlinear, high dimensional, multiclass pattern recognition problem with small samples. A support vector machine is suitable for solving this pattern recognition problem. In this paper, the principle of support vector machine was introduced, the main influence factors of rock burst were given, and a new forecast method of rock burst intensity based on one-against-one SVM classification was presented, through learning the small training samples collected from a mine, the complicated nonlinear mapping relationship between degree of rock burst and its affected factors was established by the proposed method. The case study shows that the method is feasible, easy to be implemented. So the proposed method is very attractive for a wide application in forecasting rock burst.

KEYWORDS: Soft rock roadway, supporting, fractal, loose circle, stability

 

 

Study on pre-splitting blasting for gas drainage rate improvement in heading excavation

Hongtu Wang

State and Local Joint Engineering Laboratory of Methane Drainage in Complex Coal Gas Seam, Chongqing University, Chongqing, China

Key Laboratory for Exploitation of China Southwestern Resources & Environmental Disaster Control Engineering, Ministry of Education, Chongqing University, Chongqing, China

Xiaogang Fan, Zhigang Yuan, Houxue Xu

Key Laboratory for Exploitation of China Southwestern Resources & Environmental Disaster Control Engineering, Ministry of Education, Chongqing University, Chongqing, China

ABSTRACT: To solve the problem of low excavation speed and reduce the high risk of coal and gas outburst due to low gas draining rate in heading excavation, taking a mine excavation heading as an example, the test of deep-hole pre-splitting blasting was processed. The amount of gas draining after pre-splitting was compared to the direct draining, and the effective radius of draining was surveyed. The test result showed that the draining rate of K1 coal seam reached 37.13%, which reduced the draining time by 60% 10 days after pre-splitting, and the gas desorption index exceeded the standards until the fifth blasting. It took 12 days for the draining rate to reach 34.28%, which reduced the draining time by 60%, and the gas desorption index exceeded the standards when the third blasting processed. Obviously, the effect of gas draining was improved by pre-splitting blasting. The effective draining radius of K1 and K4 were 4.5 m and 5.2 m respectively after pre-splitting blasting.

KEYWORDS: coal mine, heading excavation; pre-splitting blasting; draining radius

 

 

Analysis of the economic strength index model based on wet fiber reinforced shotcrete

Aixiang Wu, Chunlai Wang, Li Li, Bin Han, Shaoyong Wang

Civil and environmental engineering college, University of science and technology, Beijing, China

ABSTRACT: The wet fiber reinforced shotcrete is high-cost. In order to ascertain the relationship between the quantity of materials, strength and cost of wet fiber reinforced shotcrete, to obtain the reasonable and optimal mix ratio of wet fiber reinforced shotcrete, and further to reveal the rule of strength changed with different materials. The experimental research was carried out using MTS servohydraulic rock mechanics testing system. Based on the ASTM C 1 550 test standard, the strength change in the process of uniaxial compression and flexural resistance was investigated at the different ages of wet fiber reinforced shotcrete. The influence of main components quantity on the increased strength in wet fiber reinforced shotcrete was analyzed, especially the quantity of cement, plastic fiber, water reducer, accelerator, etc. A new concept of economic strength index (ESI) was put forward, and the equations of ESI about uniaxial compressive and flexural were got. The relationship was illustrated between the quantity of materials, strength and cost of wet fiber reinforced shotcrete. Results show that, when the cost is equal, high quantity of cement and water reducer could reduce ratio of water to cement and significantly enhance the uniaxial compressive and flexural strength of shotcrete at the same time according to the ESI equation. However, the increasing quantity of fiber improves the cost, enhances the residual strength of shotcrete layer and the supporting capacity of cracked shotcrete layer, but does not increase the compressive strength. In conclusion, to satisfy the supporting strength, the ESI equation effectively decreases the cost in design the mix ratio of wet fiber reinforced shotcrete.

 

 

Energy mechanism of sulphide dust explosion in sublevel mining drawing outlet for high sulphur metal ore mine

Yunzhang Rao

Jiangxi University of Science and Technology, Ganzhou, Jiangxi Province, China

Sujing Huang

Jiangxi Copper Group Co., Ltd., Dongxiang, Jiangxi Province, China

Jianping Zhang, Guangzhe Xiao

Jiangxi University of Science and Technology, Ganzhou, Jiangxi Province, China

ABSTRACT: This paper studies the ignition of sulphide dust explosion in the sublevel mining drawing outlet of high-sulphur metal mine on the basis of chemical reaction heat and energy diffusion mechanism. The study shows that the major ignition of the sulphide dust explosion is the combustion of oxidized high sulphure ore, lintel being the major explosion position.

KEYWORDS: Metal ore mine, sulphide dust explosion, spontaneous ignition

 

 

Influence of pore structure on low temperature oxidation of coal

Guanglong Dai

Anhui University of Science and Technology, Huainan, Anhui Province, China

Key Laboratory of Coal Mine Safety and Efficient Exploitation of Ministry of Education,

Huainan, Anhui province, China

ABSTRACT: Based on fractal characters of coal pore structure, mercury intrusion method was used to study pore structure in coal. Experiment of low temperature oxidation of coal was done, in order to study relationship between low temperature oxidation of coal and pore structure in it. The results showed that total pore volume, specific surface area of coal and fractal dimension value decrease with coal metamorphism degree increase. Temperature increase rate and heat release rate in coal oxidation process decrease with decrease of pore volume in coal, specific surface area and fractal dimension value. Specific surface area plays a key role in coal oxidation when pore volume in coal samples is the same.

KEYWORDS: Coal spontaneous combustion, low-temperature oxidation, pore fractal structure

 

 

Research on overburden strata deformation and protective effect with far-distance lower protective layer

Biming Shi

Anhui University of Science and Technology, Huainan, Anhui, China

ABSTRACT: Based on finite element calculation method, the dynamic process of far-distance protective layer mining is simulated by using the RFPA application system, through which the regulation of overburden strata rupture and movement, and the deformation characteristics of protected seam are gain. By investigating the gas pressure of protected seam, the permeability changes and the deformation laws of coal seam, the effects of outburst prevention by protected seam exploitation is analyzed. The experiment results at site were consistent with those results shown above, and the function mechanism were analyzed of the upper coal for optimizing collocation of unloading pressure holes and eliminating coal and gas outburst danger.

KEYWORDS: Far-distance lower protective layer, coal seam deformation, gas pressure, coal and gas outburst

 

 

Control technology of structure coupling and engineering application to inclined-shaft under abundant-water conditions

Yongping Wu, Youfu Zeng, Hongwei Wang

Xi’an University of Science and Technology, Xi’an, Shanxi Province, China

Ping Ye

Qingshuiying Coal Mine, Shenhua Ningxia Coal Industry Group Co., Ltd., Yinchuan, Ningxia, China

ABSTRACT: Deformation mechanism of roadway in abundant water-soft rock environment is more complicated than the general one, and the stability of surrounding rock for this roadway, both of which are not effectively controlled by the single and traditional supporting systems of mine workings, thus badly affecting the efficiency and safety of coal production. On the basis of controlling over the stability of surrounding rock of the No. 1 return slant at Qing shui ying coal mine, the inherent mechanism of the loss of the pre-stressed bolting and loosening between bolts and surrounding rock were analyzed, and the results showed that it resulted from the effects of groundwater, the weak rock mass, the non-coupling structure, and the irrational para-meters of anchor cable. The practice in situ testifies that a key point of control soft rock roadway was controlled water, under the condition of blanking off water, and controlling technolo-gy of multi-media structure coupling based on high-strength and pretension system, which can effectively control the soft rock roadway. In addition, the stability of surrounding rock, which was coupling support is predicted. As the expected results are obtained in the industrial test, the stability of surrounding rock for coal roadway is effectively controlled and this technique can be used to control the stability of surrounding rock for similar underground con-stitution.

KEYWORDS: Abundant water-soft rock environment, inclined-shaft, anchorage capacity invalidation, structure coupling

 

 

Construction technology of the inclined shaft through thick wind-blown sand seam

Ying Xu, Yong Sun

School of Civil Engineering and Architecture, Anhui University of Science

and Technology, Huainan, Anhui Province, China

ABSTRACT: The stratum movement failed to be kept in control, the steel brackets were broken out of torsion, and even the workers got covered up by the fallen roof when the advance support of pipe shed made of the regular steel bracket was utilized twice to tunnel through thick wind-blown sand stratum. Concrete line was unable to be poured, and construction was interrupted due to large roof collapse. To get over it, annular soil of upper bench is firstly excavated in shaft arch. The steel brackets are erected and the outer metal nets are suspended. Then the preliminary 100 mm thick concrete is shot, and the roof is supported by over-length advance condulet canopy. The inner metal nets are suspended; another 200 mm-thick shotcrete is done. The workface is sealed by grouting; the sand stratum is reinforced by condulet grouting. The achievements of smooth tunneling provide valuable experiences for the similar project.

KEYWORDS: Advance ductule, pipe shed grout, wind-blown sand stratum, inclined shaft dri-vage, short section drivage and lining

 

 

Forecast of rock burst intensity based on one-against-one SVM classification methods

Yongkui Shi, Jiansheng Shao

Shandong University of Science and Technology, Qingdao, Shandong Province, China

ABSTRACT: The rock burst is one of the major problems in deep mining. How to predict the rock burst effectively and to reduce the disaster caused by the rock burst, has great significance. The rock burst is affected by many complex factors, so the forecast of rock burst intensity is a non-linear, high dimensional, multiclass pattern recognition problem with small samples. A support vector machine is suitable for solving this pattern recognition problem. In this paper, the principle of support vector machine was introduced, the main influence factors of rock burst were given, and a new forecast method of rock burst intensity based on one-against-one SVM classification was presented, through learning the small training samples collected from a mine, the complicated nonlinear mapping relationship between degree of rock burst and its affected factors was established by the proposed method. The case study shows that the method is feasible, easy to be implemented. So the proposed method is very attractive for a wide application in forecasting rock burst.

KEYWORDS: Rock burst, SVM, MATLAB, forecast

 

 

Force analysis of the material handled by belt conveyor at loading point and in accelerated area

Linjing Xiao, Hui Sun, Kewen Sun

Shandong University of Science and Technology, Qingdao, Shandong province, China

ABSTRACT: During the transportation, the forces exerted on the material handled by the belt conveyor at the loading point and in the accelerated area are very complicated. The forces are analyzed and some mistake is found in the calculations in ISO5048.1989 (E). Firstly, the frictional resistance FAf brought by material’s momentum at the loading point is not taken into consideration. Secondly, the formulae of the resistance Ff and FgL, which are between material and baffle plates in the accelerated area and non-accelerated area respectively, are false. Then the right formulae of FAf , Ff and FgL are given.

KEYWORDS: Belt conveyor, additional resistance, inertial friction, frictional resistance

 

 

Research on moisture emendation formula for coalbed gas content by indirect methods

Zhongyou Tian

China University of Mining and Technology, Beijing, China

ABSTRACT: Using coal samples at different metamorphic stages, isothermal adsorption experiments at dryness and different moistures were carried out. The date of dryness coal emended by moisture experiential formulas, and comparing it with the date of practical determination of moisture coal. The results show that the formula of Fushun and Zhangzhancun is better than Eichenberger. When the volatiles is in the range of 33.92%~36.2%, the emendation adsorption isotherm by three moisture emendation equation is all closed to the practical value. The paper proposes to adopt Zhang zhancun formula to emend the moisture effect.

KEYWORDS: Indirect method, gas content, isothermal adsorption, moisture emendation

 

 

Selection of reasonable level of floor roadway in deep mines

Dezhong Li, Xiaohu Xi, Zunyu Xu, Xing Wang

Anhui University of Science and Technology, Huainan, Anhui Province, China

ABSTRACT: Choosing horizon of floor roadway scientifically and reasonably is the fundamental guarantee for low maintenance cost of roadway. In this paper, the option of reasonable horizon of floor roadway of deep mine was made by theoretical calculations and numerical simulation, combining with the geological conditions of Jianxin colliery, ultimately to determine the selecting sequence of reasonable normal distance of floor roadway of deep mine, it provides a scientific basis for the option and design of horizon of floor roadway of deep mine in the future.

KEYWORDS: Floor roadway, reasonable level, normal direction; FLAC simulation

 

 

MC simulation research on adsorption and desorption of methane in coal seam

Xijian Li

School of Safety Engineering, China University of Mining & Technology, Xuzhou, Jiangsu, China; School of Mining, Guizhou University, Guiyang, Guizhou, China; Guizhou Key Laboratory of Comprehensive Utilization of Non-metallic Mineral Resources, Guiyang, Guizhou, China

Baiquan Lin

School of Safety Engineering, China University of Mining & Technology, Xuzhou, Jiangsu, China

Hao Xu

School of Mining, Guizhou University, Guiyang, Guizhou, China

ABSTRACT: At present, the study of methane adsorption and desorption inside coal only stay in the level of its mechanism and invertible experiment. Study about methane molecules’ adsorption and desorption characteristic in coal pores in microcosmic level is few. In this study, relationship of macrofluid parameters and micromolecules physical quantity which represent methane adsorption and desorption characteristic was established applying thermodynamics, statistical mechanics and coal chemistry theories. Random movement of methane molecules in coal pores was simulated adopting Monte Carlo molecular simulation technology. Action of methane molecules in adsorption and desorption process was studied. Research methods of this paper have some unique characteristics. Firstly, it is an innovative method that theory of methane molecules random movement in the microcosmic was combined with thermodynamics, sta-tistical mechanics theories to study methane adsorption and desorption characteristic. Secondly, model of methane molecules’ adsorption and desorption process was established. Com-puter simulation and laboratory experiment were both used to inspect and verify each other. Thirdly, simulation program was developed adopting VC++6.0 development environment. Fourthly, re-lationship graph can be drawn between different parameters including porosity, pressure, tem-perature etc. and methane adsorption quantity adopting computer graphics visualization tech-nology.

KEYWORDS: Methane, adsorption and desorption, Monte Carlo, molecular simulation

 

 

Research on coal mine gas sensor systems based on two-wavelength

Mengran Zhou, Haiqing Zhang, Hongwei Wu

Anhui University of Science and Technology, Huainan, Anhui Province, China

ABSTRACT: Gas explosion coal mine is the major security accident, for the past shortcomings of gas detection and the detection of gas concentration measurements, which cause wrong measurement data, so two-wavelength gas sensing system is designed to reduce the error greatly. Selecting the right wavelength, the system uses the same light source and the same ab-sorption pool to eliminate the impact of the light source changing, the errors caused by different absorption parameters and interference absorption caused by background. The result shows that this method effectively improves the detection sensitivity, precision and stability.

KEYWORDS: Two-wavelength, K coefficient, error interference

 

 

Numerical simulation analysis of coal-gas outburst during excavation in coal seams

Feng Cai, Zegong Liu

Anhui University of Science and Technology, Huainan, Anhui Province, China;

Key Laboratory of Coal Mine Safety and Efficient Exploitation of Ministry of Education, Huainan, Anhui Province, China;

Key Laboratory of Integrated Coal Exploitation and Gas Extraction, AUST, Huainan,

Anhui Province, China

ABSTRACT: Coal and gas outburst is a kind of complex engineering-evoked disaster. According to the foundational theory of coal-rock deformation and gas seepage, taking consideration of nonuniform material mechanics characteristic of coal-rock medium as well as nonlinear permeability characteristic during cracking, and taking advantage of SPH method of LS-DYNA, coal-gas outburst evoked by excavation was numerically simulated. The simulation results reappeared the process of outburst: under the interaction of gas pressure, strata stress and mechanical property of coal-rock, the whole process of outburst including cracks in coal were produced, grew, penetrated each other as well as the coal were ultimately thrown out. The nonlinear essence of the process, that the gradual failure evoked sudden change under the condition of disturbance of mining activity, was revealed. And the evolution of stress field during the cracking process of gassy coal-rock was revealed. This provided theoretic foundation and scientific reference for further research on the mechanism and controlling technology of outbust.

KEYWORDS: Coal-gas outburst; SPH; solid-gas coupling; numerical simulation

 

 

Application of multi-step sectional sealing technology in gas pressure measurement in coal seam by a downward borehole

Qilin He

Key Laboratory of Coal Mine Safety and Effecient Exploitation of Ministry of Education,

Huainan, Anhui Province, China

Wei Peng

School of Energy and Safety, Anhui University of Science and Technology,

Huainan, Anhui Province, China

ABSTRACT: In order to get the exact value of gas pressure, high-pressure grouting method is used to sealing fracture around the borehole in rock, which can block the connection between the borehole and the fracture in rock. This article introduces a method that using multi-step sectional sealing technology to mesure the gas pressure in broken coal seam. An advanced method to measure the gas pressure in coal seam comes up according to a large number of actual measurements and analysis of the borehole sealing technology, which has certain value of extension and application.

 

 

Deduction analysis on development characteristics of mining induced stress shell and mining induced fracture

in deep longwall mining

Ke Yang

Key Laboratory of Integrated Coal Exploitation and Gas Extraction, Anhui University of Science

and Technology, Huainan, Anhui Province, China

Guangxiang Xie

Key Laboratory of Coal Mine Safety and Efficient Exploitation of Ministry of Education;

Anhui University of Science and Technology, Huainan, Anhui Province, China

ABSTRACT: key issue in underground mining is to understand and master distributing and evolving patterns of stress and fissure induced by mining profoundly, and to control and utilize the action of rock pressure effectively. Moving coordinate system and ellipsoid equation have been carried to construct the 3D model of MISS analysis based on rock pressure and strata behaviors of deep longwall mining in Huainan and Huaibei coal mines. Developing configuration equations of mining induced stress shell (MISS) and evolving extension of mining induced fissure (MIF) were obtained under the conditions of subcritical extraction. And the relational expressions of factors during the developing of MISS-MIF were gained by analyzing factors affected on development characteristics of MISS-MIF. Constructed model has been applied to investigate into calculating and deducing analysis on MISS and MIF with longwall mining on the strike in special geological and mining conditions. In which, development characteristics of MISS-MIF were obtained that are in conformity with experimental results. Integrated analyzing shows that 3D model is feasible in calculating and deducing development characteristics of MISS-MIF.

KEYWORDS: Longwall mining, mining-induced stress shell, mining-induced fissure, subcritical extraction, half- ellipsoid equation

 

 

Study on geothermal temperature distribution characteristics and it’s affecting factors in an Huainan Mining Area

Guangquan Xu, Zegong Liu, Weining Wang

School of Earth Science and Environmental Engineering, Anhui University

of Science and Technology, Huainan, Anhui Province, China

Peiquan Li, Xiangjin Huang

Huainan Mining Group, Huainan, Anhui Province, China

ABSTRACT: Geothermal, which brings about coal mining heat-hazard, has influence on environment of mining and at the same coal mining area, there are large different temperatures in vertical and horizontal direction. Taken Huainan coal mine as an example, after collected the hydrological drilling and geothermal data of the new and old Huainan mining area systematically, the horizontal and vertical geothermal distribution characteristics have been studied. And also the affecting factors of abnormal geothermal were analyzed. Study results show that owing to the terrain and the rock thermal conductivity, the geothermal and the geothermal gradient at the same level of the mine site are higher than the syncline anticline geothermal sites, and Quaternary loose layer is not conducive to the diffusion of geothermal; the intrusion of igneous rock causes high temperature; groundwater flowing also makes the geothermal abnormal.

KEYWORDS: geothermal hazard, geothermal distribution, affecting factor

 

 

Experimental studies on oxidation pattern of coal by TG-DSC-GC technology

Wei Peng

University of Science and Technology of China, Hefei, Anhui, China

Key Laboratory of Coal Mine Safety and Efficient Exploitation of Education Ministry of Education,

Huainan, Anhui Province, China

Anhui University of Science and Technology, Huainan, Anhui Province, China

Qi-lin He

Anhui University of Science and Technology, Huainan, Anhui Province, China

Xin-yu Ge

Zhangji Coal Mine of Huainan Mining Group, Huainan, Anhui Province, China

ABSTRACT: Coal mine fire is a common accident, and spontaneous combustion is the major cause of it. Thermo-gravimetry (TG) and Differential Scanning Calorimetry (DSC) technologies were used to study the coal oxidation process. The whole process can be divided in to 5 stages: they are moisture evaporation stage, oxygen absorption stage, thermal decomposition stage, combustion stage and burnout stage. The oxidation characteristic values of each stage were analyzed in order to find out the oxidation and spontaneous combustion pattern; TG and DSC combined with Gas Chromatography (GC) technologies were used to study the gas production pattern in the whole oxidation process of different coal. According to the study results, carbon monoxide (CO) can be used as the main index gas for the prediction of coal spontaneous combustion in the low temperature stage, and ethene (C2H4) can be used as the subsidiary one. Finally, the pattern of oxygen demand at oxidation process was proposed.

KEYWORDS: Thermal analysis, gas chromatography, coal oxidation, spontaneous combustion, index gas

 

 

Research on gas sensor fault diagnosis based on wavelet analysis and VLBP neural network

Junhao Wang, Xiangrui Meng

Anhui University of Science and Technology, Huainan, Anhui Provincee, China

ABSTRACT: For four types of common faults of gas sensor, namely offset, impact, drift and periodic types, on the basis of wavelet analysis and VLBP neural network, a method of the gas sensor fault diagnosis is proposed based on the pattern matching and classification of characteristic energy spectrum extracted by wavelet packet decomposition and VLBP neural network. Characteristic energy spectrum of each singularity can be obtained through the wavelet packet decomposition of output signal of gas sensor. After processing, it, as the characteristic vector for training VLBP neural network, adopts the momentum VLBP algorithm for updating weight values at each sample point; and, through learning a variety of characteristics data of fault mo-del, it is used to determine the fault type of sensor. The experiment result shows that, this me-thod can be effectively applied to the fault diagnosis of gas sensor.

KEYWORDS: Gas sensor, wavelet packet, VLBP neural network, fault diagnosis

 

 

Technology of interactive collecting and processing mine ventilation network information

Yingdi Yang, Guoshu Zhang

School of Energy and Safety, Anhui university of science and technology; Key Laboratory

of Coal Mine Safety and Efficient Exploitation of Ministry of Education, Huainan, Anhui, China

ABSTRACT: Aimed at the problems existing in collecting and treatment ventilation network information, the paper puts forward a method about the mine ventilation system diagram's combination of manual analysis and automatic identification, which can collect network information interactively and draw a simple ventilation system graph with GIS function and a network with face centralized layout in center, inlet air down and outlet air up; Associational branches are moved with the nodes. A simplified fixed Q method is used in network calculation, which is complete to meet the requirement. The result is shown in the network graphs. Through in situ test, the result shows that the interactive collection means is feasible; simple ventilation system is simple and intuitive; the efficiency of drawing and editing network graphs is very high; the range of searching cotree’s branches and independent loop is greatly reduced, and the velocity is improved.

KEYWORDS: Network information, interactive collection, simulation mode

 

 

Design of coal pillar with roadway driving along goaf in fully mechanized top-coal caving face

Jucai Chang, Guangxiang Xie, Ke Yang

Key Laboratory of Coal Mine Safety and Efficient Exploitation of Ministry of Education;

Anhui University of Science and Technology, Huainan, Anhui Province, China

ABSTRACT: Small coal pillar with reasonable width plays important roles in not only improving recovery ratio and eliminating dynamic disasters, but also in keeping the stability of entry surrounding rock. In order to analyze reasonable layout of gob-side entry driving in fully mechanized top-coal caving face (FMTC face), numerical simulation, in-situ measurement and theoretical calculation are carried out. The stress redistribution rules of coal mass in dip direction are put forward by metering the stress after coal extraction. At the same time, mechanical characteristics of coal pillars with different widths, 3 m, 5 m, 7 m, 10 m, 15 m and 20 m, respectively, are obtained by analyzing stress field, displacement field and fractured field characteristics. Reasonable width of district sublevel coal pillar is determined by calculating the width of limit equilibrium region and the cracked range of the entry surrounding rock due to mining of adjacent face based on the results of in-situ measurement and numerical simulation. The engineering practice proves that the width of coal pillar is scientific and reliable. It provides a scientific basis for reasonable layout of gates and determining parameters of the coal pillar in FMTC face. It can be favorable to improve maintenance states of entry, and also benefit to improve the recovery in FMTC face, and it provides beneficial lessons for determining reasonable width of gob-side entry driving of other similar conditions.

KEYWORDS: Fully mechanized top-coal caving face, roadway driving along goaf, coal pillar width

 

 

Roadside supporting design for gob-side entry retaining and engineering practice

Yingfu Li

Key Laboratory of Coal Mine Safety and Efficient Exploitation of Ministry of Education;

Anhui University of Science and Technology, Huainan, Anhui Province, China

Xinzhu Hua

Anhui University of Science and Technology, Huainan, Anhui Province, China

ABSTRACT: In order to determine the width of roadside backfilling body, new mechanical model of roadside supporting resistance is established based on taking the dip angle of coal seam and supporting force of roadside coal seam into account. Based on this model, computational formulas of roadside supporting resistance and supporting force of roadside coal seam are derived, and function mechanism of roadway-in bolting support is analyzed. Moreover, the technique of advancing roadside combined support is proposed to solve the problem of hysteretic support of roadside backfilling body, to provide early stronger roadside supporting force, and to improve self-bearing capacity of roof strata. The technique is that a gap is made in advance at the end of the working face and combined support of bolting, cable, steel strip, and wire netting is adopted to support the gap roof. According to the theoretical analysis, a roadside supporting design is made for haulage entry of No. 512(5) working face in Xieyi mine of Huainan, and the function relationships are explored between roadside supporting resistance and the width of roadside backfilling body, the dip angle of coal seam, roadway width, feature size of fractured roof strata, supporting resistance of roadway roof.

KEYWORDS: Mechanical model, roadside supporting resistance, roadside supporting de-sign

 

 

Research on a new structure of bolt-end based on broken mechanism of FRP bolt

Yingming Li

Key Laboratory of Coal Mine Safety and Efficient Exploitation of Ministry of Education; Anhui University of Science and Technology, Huainan, Anhui Province, China

Nianjie Ma

School of Resources and Safety, China University of Mining and Technology, Beijing, China

ABSTRACT: The failure of bolt-end often occurs when roadway rib is supported by bolt. The broken mechanism of FRP bolt is revealed by mechanics analysis. Its broken mechanism can be summarized that bolt-end stress increases rapidly under an eccentric load, which leads to a break at this point and then spreads to the entire cross-section. A new structure of FRP bolt-end called metal sleeve-indentation is presented and manufactured based on its broken mechanism and by studying the structure of FRP bolt-end. These experimental results under normal and eccentric load show that the new FRP bolt with new bolt-end structure not only has perfect connection feature but also has proofed eccentric breaking capacity.

KEYWORDS: Coal rib supporting, FRP bolt, bolt-end, eccentric load, round indentation

 

 

Research on a new structure of bolt-end based on broken mechanism of FRP bolt

Yingming Li

Key Laboratory of Coal Mine Safety and Efficient Exploitation of Ministry of Education; Anhui University of Science and Technology, Huainan, Anhui Province, China

Nianjie Ma

School of Resources and Safety, China University of Mining and Technology, Beijing, China

ABSTRACT: The failure of bolt-end often occurs when roadway rib is supported by bolt. The broken mechanism of FRP bolt is revealed by mechanics analysis. Its broken mechanism can be summarized that bolt-end stress increases rapidly under an eccentric load, which leads to a break at this point and then spreads to the entire cross-section. A new structure of FRP bolt-end called metal sleeve-indentation is presented and manufactured based on its broken mechanism and by studying the structure of FRP bolt-end. These experimental results under normal and eccentric load show that the new FRP bolt with new bolt-end structure not only has perfect connection feature but also has proofed eccentric breaking capacity.

KEYWORDS: Coal rib supporting, FRP bolt, bolt-end, eccentric load, round indentation

 

 

Research on deformation and failure laws of aquifuge of coal seam floor during pressurized working

Zhaoning Gao

School of Energy and Safety, Anhui University of Science and Technology, Huainan, Anhui Province, China

Xiangrui Meng, Xiangqian Wang

Key Laboratory of Coal Mine Safety and Efficient Exploitation of Ministry of Education, Huainan, Anhui Province, China

ABSTRACT: Taking into consideration of the geological conditions of Face 1028 of Suntuan Coal Mine of Huaibei Group Limited of Mining Industry, the present research on the simulation of the dynamic process of the coal seam under working is conducted by turning to numerical analysis, with the aim of observing the laws governing the floor stress and displacement variations as the working face advances. It is concluded that the floor stress and displacement are always dynamic, leading to the difference between the displacements of the front and back of working face. Through analysis, the difference is attributed to the fact that before working, the stress is accumulated; after working, the stress is relieved and then restored, hence the added stress. Then theoretical analysis is turned to in order to analyze the damage factors of the floor under working, leading to the conclusion that the depth of floor failure serves as a function of the internal friction angle φ, the uniaxial compression strength σc, the maximum compression strength coefficient n and the working depth H. Based on the results, measures are put forward for the reduction of the floor failure. For the sake of earliest possible monitoring, prediction and prevention of the floor water burst from the working face and goaf, investigations are con-ducted into the floor failure depth and the working fissures for Face 1028 of Suntuan Mine by turning to direct current conductivity CT.

KEYWORDS: pressurized working, displacement difference, floor deformation and failure

 

 

Experimental study on strength development law of filling body in gob-side entry retaining

Xiaoyu Lu

School of Energy and Safety, Anhui University of Science and Technology,

Huainan, Anhui Province, China

Liang Yuan

National Engineering Research Center for Coal Mine Gas Controlling,

Huainan, Anhui Province, China

Xinzhu Hua

Key Laboratory of Coal Mine Safety and Efficient Exploitation of Ministry of Education,

Huainan, Anhui Province, China

ABSTRACT: The uniaxial compressive and splitting tension strengths exhibit two important mechanical properties of filling body in gob-side entry retaining. Therefore, experimental study on the strength development law of filling body was conducted. The specimens were fabricated in Xieyi mine. The uniaxial compressive and splitting tension strengths were tested at different curing aging time of 1, 3, 7 and 28 days. Finally, regressive formulas are given to describe the relationship between the strength and aging time. The strength increases very quickly in the first 3 days, and the strength in 3 to 7 days increases a bit more slowly than in the first 3 days, and the strength in the latter 21 day increases much more slowly than in the first 7 days. The uniaxial compressive and splitting tension strengths of 3 days aging time and 7 days aging time can reach about 35% and 60% of that of 28 days aging time, respectively.

KEYWORDS: Gob-side entry retaining, uniaxial compressive strength, splitting tension strength

 

 

Wet shotcreting dual-mode design and dynamic zoning support mechanism and technology for deep shaft

Yunhai Cheng

Key Laboratory of Coal Mine Safety and Efficient Exploitation of Ministry of Education,

Anhui University of Science and Technology, Huainan, Anhui Province, China

Guandong Wang

Technical Center of Xinwen Mining Industry Group, Xintai, Shandong Province, China

Shanxin Guo

Technical Center of Xinwen Mining Industry Group, Xintai, Shandong Province, China

ABSTRACT: A dual-mode system suitable for wet shotcreting of deep shaft workings is propo-sed. Dynamic zoning support principle and technology has been proposed based on the mechanism of deep shaft concrete, making the wet shotcreting design can adapt to the rock surrounding conditions and stresses variation. Through system mechanics experiments, the result shows that the wet shotcreting and dry shotcreting have the same support effect while the design thick-ness of wet shotcreting is 83% of dry shotcreting, and the wet shotcreting saves 17% material. Application shows that the dust concentration of wet shotcreting is about 1/7 of the national standard (dust concentration of dry shotcreting is nearly 10 times of the national standard), realizing non-respirable dust basically and avoiding the hazard of workers' breathing respirable dust, which completely changes the phenomenon of dust diffusing situation in the past. Wet shotcreting reduces rebound ratio approximately 12%. The uniaxial compressive strength of wet shotcreting is about 1.48 times of dry shotcreting, which enhances the support effect. The above study shows that deep shaft wet shotcreting achieves an ideal effect.

 

 

Experimental study on the influence of effective confining pressure on liquid permeability in coal seam

Pin Lv, Zhisheng Wang, Li Huang

Key Laboratory of Coal Mine Safety and Efficient Exploitation of Ministry of Education;

Anhui University of Science and Technology, Huainan, Anhui Province, China

ABSTRACT: There exists obvious effect of fluid-solid coupling during process of coal seam water infusion when water is injected into coal seam, the relationship between coal permeability and confining pressure was studied by self-made coal permeability testing equipment. The fitted equations of coal permeability were obtained, which demonstrated the interaction between coal permeability and confining pressure. On the basis of experimental data, the sensitivity coefficient Ck of permeability under stress was gotten. The results show that the permeability of different coal will drop regularly along with the increasing of the confining pressure, and meet the mathematic relationship of quadratic polynomial; different permeability of coal sample has similar sensitivity to the change of confining pressure.

KEYWORDS: Effective confining pressure, coal permeability, seepage

 

 

Deformation properties and control models of surrounding rock in deep mines with complicated geological conditions

Wenhua Zha, Xinzhu Hua

Key Laboratory of Coal Mine Safety and Efficient Exploitation

of Ministry of Education, Huainan, Anhui Province, China

ABSTRACT: The supporting technology of roadway in deep mine with complicated geological conditions is discussed. According to the complicated geological conditions in deep mine at Yuandian Mine, supporting effects of roadway based on existing supporting programs are monitored on-site. The deformation behavior of roadway is obtained and the causes of instability of surrounding rock are analyzed. Supporting principles and control model are proposed pertinently, providing reference for further decision-making of supporting programs in roadway.

KEYWORDS: Deep mine, complicated geological conditions, deformation properties of surrounding rock, control model

 

 

Analysis of the dynamic stability of hard and thick strata of overlying multilayer spatial structures in deep coal mines and its application

Hong Shi

Shandong Jiaotong University, Jinan, Shandong Province, China

Huajun Wang

Bijie University, Bijie, Guizhou Province, China

Shandong University of Science and Technology, Qingdao, Shandong Province, China

Yankuang Group, Zoucheng, Shandong Province, China

ABSTRACT: According to the characteristics of sediment rock and the movement of hard and thick strata of overlying multilayer spatial structures in deep coal mine, by using the dynamic stability judgment rules controlled by the top coal’s recovery ratio, the author worked out the judgment curves of dynamic stability of hard and thick strata and explained their application. This paper also analyzes the factors influencing the dynamic stability, and concludes that the thickness of key strata is the main factor influencing the stability of the whole roof deformation; the stability of the part contact of the main roof is influenced by the friction characteristic, the thickness and intensity of hard and thick strata; and the preternatural pressure at caving face is mainly caused by the instability of the part contact of the main roof. The suggested judgment rule and curve of dynamic stability have been tested by field experiments which achieved safe caving in isolated caving face by adjusting the top coal’s recovery ratio. The theoretical basis of designing the safe top coal’s recovery ratio can be provided according to different overlying strata, and the safe overlying strata controlling can be achieved in deep coal mining.

 

 

Study on dust collection and removal systems in heading face based on air curtain technology

Yucheng Li, Jian Liu, Bo Liu

Liaoning Technical University, Fuxin, Liaoning Province, China

ABSTRACT: This paper analyzes the present situation of research and application on controlling of coal-dust and air curtain technology at heading face domestic and abroad, analyzes the generation, distribution and migration rule of dust at heading face. without changing the original long-exhausted and short-forced ventilation system, it take the dry-type dust collection as starting point, seed a methods for dust control by using air curtain to collect dust and using windsocks to draw out dust, which can help to achieve the purpose of dust control at heading face. According to the theory of narrow-channel jet, the author devises a jet machine which could form an air curtain, analyzes the airflow field of pressure-in and draw-out style, demonstrates the mechanism of dust collection by air curtain, and forms the dust collection and control system by air curtain. By means such as theoretical analysis, numerical simulation, testing in laboratory, field testing and practical application in the pit etc., the research demonstrates the effect of U-shaped air curtain on dust control, especially on controlling of respirable dust, which has an obviously effect on reducing the dust concentration at heading face, in particular on reducing the diffusion of respirable dust to the driver. More over, the effect of air-curtain dust-collection and control system depends on design parameters of it, especially the width of the exit of air curtain jet-equipment and outlet air velocity of the jet. According to the theoretical and experimental analysis, this paper come to a conclusion that air curtain of the jet-equipment can completely play the role of dust collection, when the outlet air velocity of the jet lies between 10 to 20m/s and the width of the jet exit lies between 6 to 20 mm. This conclusion can provide a theoretical basis for field application of the jet machine.

KEYWORDS: Dust control, air curtain, dust collection and removal system, narrow-channel jet

 

 

Study on coal samples’ acoustic emission law in triaxial unloading compression with confining pressure

Hua Nan

School of Energy Science and Engineering, Henan Polytechnic University, Jaozuo,

Henan Province, China

Yingming Wen

Longshan Coal Mine, Anyang Xinlong Coal Group, Anyang, Henan Province, China

ABSTRACT: In order to find out the acoustic emission law in triaxial unloading compression with confining pressure experiments of coal samples from Qian Qiu Coal Mine are made by using of RMT-150B rock mechanics experiment machine. In experiments of triaxial unloading compression with confining pressure, almost no acoustic emission appears during compaction state, and there is a little acoustic emission before unloading confining pressure and the coal samples’ acoustic emission frequency and energy is ratio to time, and there is a sharp increasing of acoustic emission frequency during unloading confining pressure. However, there is an obvious increasing of acoustic emission frequency and energy near their damaged point and it get the maximum value when they are damaged.

KEYWORDS: Coal samples, acoustic emission, triaxial unloading compression, confining pres-sure

 

 

Study on pre-evaluation model of support effect on mining roadways based on CBR

Xiangqian Wang, Xiangrui Meng, Zhaoning Gao, Huizong Li

Anhui University of Science and Technology, Huainan, Anhui Province, China

Feng Zhong

Zhejiang International Studies University, Hangzhou,Zhejiang Province, China

ABSTRACT: In view of the requirements of pre-evaluation on support effect for mining roadways and the working theory of case-based reasoning (CBR for short), a pre-evaluation model is established based on CBR, in which case representation, case retrieval, case revise and other key techniques of CBR have been discussed. The model offers a new and feasible way to pre-evaluation of support effects on mining roadway.

KEYWORDS: CBR, pre-evaluation model, support effect

 

 

Future perspectives of the coal mining sector in Poland

Zbigniew Rak, Jerzy Stasica, Zbigniew Burtan

AGH University of Science and Technology, Krakow, Poland

ABSTRACT: The foresight project “Scenarios of technological developments in the coal mining sector” allows for defining the conditions and scenarios of underground mining in Poland. This study briefly summarises the research work involved in the project whose main purpose is to define the directions for further development of the coal mining sector in Poland. The conditions for the development of various mining systems are explored and applicability of selected systems is investigated in the context of the above criteria.

 

 

Injectory firming of a rock mass in the area of rebuilding an excavation as a way to prevent rocks from falling and from the results of these fallings

Tadeusz Rembielak, Dariusz Chlebowski

AGH University of Science and Technology, Krakow, Poland

ABSTRACT: A series of rebuilding of excavations with a corroded ŁP lining was performed in the KWK “Piast” mine, without a necessity of limiting their basic “motion” functions. One of the ways to increase safety during performing the rebuilding of crossroads and forks is applying injectory rock mass firming in their surrounding. An example of a rebuilding technology of the crossing 652 with by-pass to the shaft 3 on the level of 650 meters was presented in the paper.

 

 

Technologies used to reinforce preparatory headings before longwall exploitation front in conditions of Polish hard coal mines

Jerzy Stasica

AGH University of Science and Technology, Krakow, Poland

ABSTRACT: This article presents technologies used to strengthen preparatory headings in the conditions of Polish hard coal mines. The researchers focused on the need to reinforce the linings of headings, especially those at longwalls, which are subject to frequent deformations in areas of exploitation pressures in front of and behind longwall exploitation fronts and at cros-sings with exploitation longwalls. The analysis conducted pointed out directions of development in the reinforcement technologies provided while driving the headings discussed, and while maintaining them in various mining situations.

 

 

Comparison of methods used in Poland for the evaluation of dewatering wells

Krzysztof Polak, Karolina Kaznowska

AGH University of Science and Technology, Krakow, Poland

ABSTRACT: Wells are the key element of the drainage system in lignite mining in Poland. Currently, more than thousand are in operation, pumping groundwater in quantities reaching 1000 m3/min. Because of their use, mining wells work in extreme conditions. In contrast to public groundwater intakes, their task is to cause depression of groundwater, allowing safe lignite exploitation. Working conditions result in accelerated aging of wells’ filters. This increases the hydraulic and energy losses. To reduce the losses, it is necessary to objectively assess the technical status, what allows to decide whether to renovate wells or drill new ones. Assessment of the wells is conducted basing on the macroscopic or parametric methods. The article presents a comparison of parametric methods. This comparison was based on the interpretation of pumping test results. The study was conducted in a selected deep well, belonging to AGH-University of Science and Technology.

 

 

Mechanised sublevel caving systems for winning thick and steep hard coal beds

Zbigniew Rak

AGH University of Science and Technology, Krakow, Poland

ABSTRACT: This article presents a process for mechanised exploitation of a steeply inclined, thick coal bed. It presents the mine face mechanisation method, organisation of works, and the scope of preparatory works. The system was developed and implemented in 2002 for the purpose of exploitation of a bed approximately 20 m thick inclined at 45° under the mining and geological conditions of the Kazimierz-Juliusz Sosnowiec Hard Coal mine in Poland. The production output and the system efficiency assessment have been illustrated on the basis of previous experience at that mine.

 

 

Exploitation of thin hard coal beds in Poland – strategic decisions at the threshold of the 21st century

Artur Dyczko, Jacek Jarosz

Mineral and Energy Economy Research Institute of Polish Academy of Sciences, Krakow Poland

ABSTRACT: The article discusses coal mining situation in Poland. It also defines hard coal deposits classification depending on their thickness, and presents the condition of recoverable and operative resources according to bed thickness, as well as presents their share in up to 1.5 m thick deposit production. The directions of thin beds exploitation technology development in national conditions have been signalized and a need to change the place of thin beds in the structure of hard coal mining in Poland has been shown.

KEYWORDS: mining, resources, hard coal, thin beds

 

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