矿业科学学报

Conception of in-situ fluidization mining for deep metal mines

Wu Aixiang, Wang Hongjiang, Yin Shenghua, Ruan Zhuen

2021, 6(3): 255-260. doi: 10.19606/j.cnki.jmst.2021.03.001

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Abstract:
With the depletion of shallow surface metal mineral resources, China's underground metal mining was gradually transferred to deep mining (>1 000 m).Because of the special mining conditions of high stress, great lifting depth, and high temperature in deep mines, it is difficult to realize the safe, efficient, and economical exploitation of deep resources by using the traditional mining methodology.According to the trend of deep metal mineral resources, a novel idea of in-situ fluidization mining for deep metal mines was proposed.The definition, conception, and challenges were introduced.According to the transformation methods, in-situ fluidization mining can be divided into two parts: in-situ leaching mining, and integration of mining, processing and backfilling.Moreover, the major issues and challenges faced with in-situ fluidization mining, namely, deep rock mechanics, in-situ leaching mining theory, equipment of integration of mining, processing and backfilling, environment monitoring and reconstruction, intelligent and efficient mining, were expound.

Key technologies and prospect for in-situ gasification mining of deep coal resources

Liu Shuqin, Chang Zhibing, Liu Jinchang

2021, 6(3): 261-270. doi: 10.19606/j.cnki.jmst.2021.03.002

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Abstract:
China has rich reserves of deep coal resources, and underground coal gasification can transform coal into gas and transport it to the ground, which is an important way for in-situ fluidized mining of deep coal.This article introduces the development history and technical status of underground coal gasification technology (UCG), as well as typical cases of underground coal gasification in the middle and deep parts.Based on the modern underground coal gasification technology system, the key technologies and technical research directions of deep underground coal gasification was analyzed and the prospect of deep coal gasification mining with the goal of natural gas production was outlooked.The development trend of UCG is from the mine type to the drilling type, from shallow coal seams to deep coal seams, from single power generation to comprehensive utilization.The practice of UCG in the middle and deep coal seams has verified the technical feasibility.The key technologies of deep underground coal gasification mainly include geological evaluation and scientific site selection, gasifier construction, deep coal seam high-pressure ignition, controllable mobile injection and deep fire zone geophysical detection.Deep coal gasification to produce natural gas can not only realize the clean and efficient use of deep coal resources, but also solve the contradiction between supply and demand caused by the increase in natural gas consumption.

Technological conception of in-situ pulverized coal combustion and explosion power generation based on the deep fluidization mining

Nie Baisheng, Gong Jie, Wang Xiaotong, Peng Chao

2021, 6(3): 271-279. doi: 10.19606/j.cnki.jmst.2021.03.003

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Abstract:
Aiming at solving the problems of underground coal dust pollution and low energy efficiency of traditional coal combustion, the energy utilization mode of pulverized coal explosion power generation in the process of fluidized mining was proposed.In fluidization mining in underground coal mines, pulverized coal is used simultaneously as fuel and mixed with corresponding combustion supporting agents to induce pulverized coal combustion and explosion.The energy generated by detonation is used to drive the generator to generate electricity, which will reduce the energy loss from transferring chemical energy to steam internal energy and then to mechanical energy in traditional coal-fired power generation.After dust removal and purification, the explosive residue is backfilled into the goaf to avoid the goaf collapse and promote the resource utilization of the waste.Waste heat and energy, through efficient recovery, can be used for heating to promote multi-level utilization of energy.The technical conception of fluidized mining coal combustion and explosion power generation will promote the improvement of the energy utilization rate of coal resources and push the development of the clean, efficient, safe, and intelligent use of coal resources.

Experimental study on influence factors in damage-permeability characteristics of loading and unloading coal

Xu Chao, Qin Liangliang, Li Xiaomin, Yang Gang, Sun Haoshi

2021, 6(3): 280-289. doi: 10.19606/j.cnki.jmst.2021.03.004

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Abstract:
In the process of deep coal seam mining, multiple factors affect the coal body damage-permeability characteristics.In order to reveal the evolution law of coal mining damage-permeability characteristics, the coal damage-permeability experiments under three mechanical paths of fixed confining pressure and increased axial pressure (path 1), fixed axial pressure and decreased confining pressure (path 2), increased axial pressure and decreased confining pressure (path 3) were carried out under different engineering conditions.Then the influence of factors such as loading and unloading methods, axial pressure loading rate, confining pressure unloading rate, and confining pressure on coal damage-permeability characteristics were analyzed.The results show that the different loading and unloading methods significantly affect the degree of sample damage, whose order is: path 1 < path 2 < path 3.The compressive strength of samples is easier to achieve with an increased rate of loading and unloading, but the extent of damage and permeability increase along with it.With the increase of confining pressure, the time response of damage becomes slow and the ultimate recovery degree of permeability decreases.The damage and permeability characteristics of coal have significant confining pressure effects.The cumulative amount of energy changes with time in an exponential function, and the relative permeability k/k₀ after damage expansion is in a power function.

Review of time-dependent fracture model of concrete

Chen Yulong, Cao Peng

2021, 6(3): 290-295. doi: 10.19606/j.cnki.jmst.2021.03.005

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Abstract:
The integrity of concrete structures under strong earthquakes and the stability of concrete structures with cracks are concerns of national security strategies.These two issues are closely related to the time-dependent fracture behavior of concrete.The time-domain dependent fracture behavior of concrete can be generalized into two aspects: short-term impact fracture under dynamic impact load and long-term steady-state creep fracture failure.Although they both are related to time, there is a huge difference in the loading time, which leads to the different internal mechanism of dynamic failure in concrete.Herein, the development history and main achievements of time-dependent fracture model of concrete are reviewed, including macroscopic fracture mechanics model and method, mesoscopic fracture mechanics model and method, dynamic fracture, and creep fracture behavior of concrete.

Novel reverse-circulated excavating-drilling fluidized mining technique for steep-inclined coal seam

Zhang Hongwei, Cheng Jingyi, Zhao Yinxin, Li Yang, Wan Zhijun, Wang Chunyao

2021, 6(3): 296-304. doi: 10.19606/j.cnki.jmst.2021.03.006

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Abstract:
The steep-inclined coal seams are widely distributed in western and southern China.These coal seams are complex and difficult for fully-mechanized coal mining.Therefore, developing a novel fluidized and intelligent mining method to recovery the steep-inclined coal seam is of great significance to ensure the safety production of coal.This paper proposed a reverse-circulated excavating-drilling method.A novel fluidized reverse-circulated mining machine was designed and the composition and utilization of this machine were introduced.Afterwards, the parallel excavating and drilling method of this machine is proposed.Finally, the coal mining efficiency, recovery rate and high-pressure water jet assisted coal cutting of this method were calculated.Results show that a larger diameter of cutting head always implies a greater coal mining efficiency.It is necessary to select a suitable diameter and overlap length of the cutter head according to the geological conditions and the target recovery rate of coal seam.It is found that the annual coal production linearly increased with the increasing cutter head advancing speed.Furthermore, a suitable drilling speed parameter and the utilization of the high-pressure water jet are both important to the increase of coal production.

Study on pitting mechanism of rebar rockbolt in highly-mineralized mine water

Chu Xiaowei, Ju Wenjun, Fu Yukai

2021, 6(3): 305-313. doi: 10.19606/j.cnki.jmst.2021.03.007

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Abstract:
Corrosion and abnormal failure of rockbolts often occur in the mine water and complex environment.It is found that local corrosion such as pitting is usually the main origin of corrosion failure.Pitting process and mechanism in simulating corrosive mine water of four rockbolts were tested and analyzed with a comprehensive method including metallographic examination, electrochemical experiments and video microscope.The results showed that rockbolt steel was prone to pitting corrosion due to the inclusions.The pitting mechanism was as follows: The inclusions were preferentially dissolved, producing granular corrosion products and forming interface grooves.Local acidification in grooves accelerated the dissolution and exfoliation of matrix and inclusions, which produced etching pits.The acceleration effect of interface grooves on corrosion was verified by the comparison of polarization curves of different electrodes.

Study on floor heave mechanism and control technology of roadway based on slip line field theory

Cheng Hui, Zhao Hongbao, Xu Jianfeng, Qin Fengyuan, Zhang Yixiao, Hu Linfeng

2021, 6(3): 314-322. doi: 10.19606/j.cnki.jmst.2021.03.008

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Abstract:
Based on the slip line field theory, the slip line field model of roadway floor is established.Taking 1021 roadway of Huipodi coal mine in Shanxi Province as the engineering background, the mechanism of asymmetric floor heave of roadway is studied, and the reasonable prevention and control technology of floor heave is put forward.The results show that: There are uniform stress field and non-uniform stress field in the stress field of roadway floor slip line.From the two sides to the center line of the roadway, the floor stress decreases gradually; The velocity of the active zone of the floor slip line is vertical downward.The transition zone rotates and compresses the passive zone due to the extrusion of the active zone.The passive zone moves upward, resulting in floor heave.Due to the stress concentration of isolated pillar in Huipodi coal mine, the abutment pressure on both sides of the roadway is asymmetric.The abutment pressure near the coal pillar forms a slip line field on the floor, and the direction of the velocity field points to the side of the roadway far away from the pillar.Therefore, the floor heave of 1021 roadway is asymmetric, and the floor heave height at the side far away from the pillar is larger.According to the characteristics of sliding floor heave in 1021 roadway, asymmetric support with parallel arrangement of single anchor cable is adopted to prevent floor heave of roadway, and the application effect is good.

Study on collaborative pressure relief control technology for surrounding rock stability of dynamic pressure roadway in coal mine

Wang Jiong, Liu Peng, Liu Shuai, Ma Lei, Liu Yipeng, Chen Xu

2021, 6(3): 323-332. doi: 10.19606/j.cnki.jmst.2021.03.009

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Abstract:
The stability of surrounding rock of dynamic pressure roadway in coal mine is very important to ensure the safety of mine production.In order to effectively control the instability deformation of roadway under the influence of mining pressure, taking the dynamic pressure roadway of 2201 working face in Detong Coal Mine as the engineering background, through the analysis of the failure phenomenon of dynamic pressure roadway and the evolution law of surrounding rock stress, this paper puts forward the stability control technology of dynamic pressure roadway cooperative pressure relief surrounding rock.This technology based on two-way cumulative presplitting blasting roof cutting pressure relief and constant resistance large deformation anchor cable yield pressure support.The research shows that the periodic superposition of mining dynamic pressure makes the vertical stress concentration of roadway surrounding rock and the distribution of double-peak arch asymmetry.The deformation of roadway is parabolic, and the roadway in the area with the maximum stress concentration and displacement is prone to instability.Therefore, the dynamic pressure transmission path was effectively cut off after the two-way cumulative presplitting blasting was applied to the dynamic pressure roadway, and the peak stress difference of the roadway was reduced by 19.6 %.After that, the constant resistance and large deformation anchor cable yield pressure support was applied to unloading dynamic pressure, and the reduction rate of roadway section was reduced from 60 % to 13 %.The influence of mining dynamic pressure on the stability of roadway was significantly weakened, which proved that the application effect of the stability control technology of surrounding rock with cooperative pressure relief was good, and it could provide useful guidance for similar mines.

Research on occupational health damage assessment model of coal-fired power generation during the life cycle

Wang Wei, Yao Jianting, Chen Xingbang, Tong Ruipeng

2021, 6(3): 333-341. doi: 10.19606/j.cnki.jmst.2021.03.010

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Abstract:
The coal power industry, while promoting the national economic and social development of China, also causes environmental pollution, thus threatening the health of employees and nearby residents.In order to evaluate the impact of occupational health damage factors in the life cycle of coal-fired power generation, an occupational health damage assessment system for coal-fired power generation is constructed based on LCA theory.Firstly, according to the actual situation of coal-fired power industry, this paper divides the life cycle of coal-fired power generation into different stages, then identifies the occupational health damage factors existing in each stage and carries out the process inventory analysis.Finally, through the characteristic and monetization analysis, a quantitative evaluation of occupational health damage in the life cycle of coal-fired power generation is achieved.The empirical analysis shows that among all the occupational health damage factors in the life cycle of coal-fired power generation and SO₂ causes the most serious health damage to human body.The evaluation results can provide a basis for health management and decision-making in coal-fired power industry.

CFX-based numerical simulation of pipeline leakage of coal mine main gas drainage system

Cai Jitao, Zhang Zhijing, Wang Jiefeng, Lü Wei, Zhang Weidong

2021, 6(3): 342-347. doi: 10.19606/j.cnki.jmst.2021.03.011

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Abstract:
To understand the pipeline leakage characteristics of the large-scale main gas drainage system in coal mines and the multi-physical fields of the gas flow in pipeline, a three-dimensional numerical model is developed based on Ansys CFX and the process of gas drainage pipeline leakage is investigated.The influence of different leakage positions, different leakage intensities, and different negative pressures of the pumping station on the gas flow in the gas drainage pipeline is studied.The results show that the leakage intensity and the negative pressure are the important factors affecting the internal gas flow field in the gas drainage pipeline, and the leakage occurring near the pumping station of main gas drainage system is prone to be captured easily.The results of this paper are expected to provide technical support for the safety prevention and control of pipeline leakage accidents in the main gas drainage system and also suggestions for the optimization of the allocation of safety prevention and control resources.

Analysis of the influence of ventilation on fire in underground cable roadway of coal mine

Gui Xiaohong, You Jianping, Su Shujun, Li Ying, Li Wei

2021, 6(3): 348-355. doi: 10.19606/j.cnki.jmst.2021.03.012

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Abstract:
In order to study the influence of different ventilation times on the fire of cable roadway in coal mine and provide reference for fire prevention and control of cable roadway in industrial and mining areas, a full-scale model of a cable roadway was established by FDS fire simulation software.Four ventilation conditions of 0, 2, 4 and 6 ventilation times per hour were simulated.The low velocity N-S equation driven by heat was solved by numerical method, and the smoke distribution, air concentration distribution and roof temperature change of fire source were obtained under the four working conditions.The relationship between the farthest ventilation distance and ventilation frequency was determined by analyzing the simulation data.The minimum smoke diffusion distance on the upwind side of the fire source was calculated to be 50.8 m.The simulation results show that: on the upwind side of the fire source, when the wind speed is less than 1.70 m/s, the time when the smoke reaches the farthest diffusion distance increases with the increase of wind speed; when the wind speed is greater than 1.70 m/s, the time when the flue gas reaches the farthest diffusion distance decreases with the increase of wind speed; the upwind side of the fire source is located at the upper part of the fire source, and the high temperature flue gas cannot diffuse and accumulate continuously, while the lower part has less smoke, which can not block the effect of wind flow.The results show that the air content difference between the upper and lower parts is more obvious when it is carried to the downwind side by the air flow, while in the downwind side of the fire source, the air flow is consistent with the smoke diffusion direction, and the air flow accelerates the smoke diffusion, making the air content in the upper and lower parts of the downwind side at a more uniform level; the ventilation frequency has no obvious effect on the time of reaching the stable temperature of the fire source ceiling, but has a certain impact on its temperature.

Research on talent training mode for intelligent mining

Huang Hui, Zhou Wenshan, Liu Haibin

2021, 6(3): 356-363. doi: 10.19606/j.cnki.jmst.2021.03.013

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Abstract:
Based on the large-scale application of high technology such as the Internet of Things, cloud computing, big data, artificial intelligence in the mining industry and the rapid development of intelligent mining.This paper analyzes the current development situation of intelligent mining and the talent training models of mining engineering major at home and abroad, as well as the existing problems of China's talent training mode. From the three perspectives of government policy support, school teaching system and enterprise talent demand, it puts forward some suggestions on the establishment of a talent training model that adapts to intelligent mining, so as to cultivate innovative talents and realize the scientific application and development of intelligent mining.

Study on the effect of altitude hypoxia environment on cardiopulmonary function of working miners

Yang Sanjun, Geng Ruiyuan, Liu Chunyan

2021, 6(3): 364-370. doi: 10.19606/j.cnki.jmst.2021.03.014

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Abstract:
In order to promote the cardiopulmonary function and health of miners in plateau areas, this paper uses scientific methods such as questionnaire survey, mathematical statistics and comparative analysis to test the cardiopulmonary function of healthy adult miners in Chian Tyrone, Tibet (high altitude area) and Kailuan, Hebei(low altitude area), and studies the test results from three dimensions of ventilation index, metabolic index and heart rate variability index.The results showed that there were significant differences in ventilation index, metabolism index and heart rate variability index between the plateau miners and the plain miners, and the indexes showed that the cardiopulmonary function of the plateau miners was significantly weaker than that of the plain miners.Based on the above research results, some suggestions were put forward to improve the cardiopulmonary function of plateau miners.This research has certain reference value and significance for improving the health of miners working on plateaus.

2021 Vol. 6, No. 3