CHINA MINE ENGINEERING

Abstract:In order to further improve the strength and toughness of mining mill balls, Box-Behnken design-response surface method (BBD-RSM) was adopted in this paper. Austenitizing temperature, austenitizing holding time, tempering temperature and tempering holding time were selected as independent variable influencing factors, Rockwell hardness and impact toughness of mill balls were taken as response target values, and a polynomial regression equation model was established. At the same time, OM, SEM, XRD and other analytical methods were used to study the microstructure and phase characteristics of the grinding ball under different heat treatment conditions. The results show that the significant effects of heat treatment parameters on the hardness of the ball are in the order of tempering temperature ＞ austenitizing temperature ＞ austenitizing holding time ＞ tempering holding time, and the significant effects on the impact toughness of the ball are in the order of tempering temperature ＞ tempering holding time ＞ austenitizing temperature ＞ austenitizing holding time. The optimum heat treatment parameters were obtained as follows: austenitizing temperature 885℃, austenitizing holding time 4.8h, tempering temperature 400℃, tempering holding time 3.5h, Rockwell hardness of 59.84HRC, impact toughness of 6.16J, and the relative error of verification experiment was ＜ 5%. It is proved that the response surface method is accurate and scientific in optimizing the heat treatment parameters of grinding ball. The content of alloying elements in austenite, the size, shape and distribution of carbides, the transformation behavior and proportion of residual austenite are the main reasons for the regular change of Rockwell hardness and impact work of grinding ball.

Abstract:An iron mine is a large deep open pit. After the completion of open-pit mining, it will be transferred to underground mining. In order to block the hydraulic channel between the open pit and the underground, and maintain the stability of the high and steep slope, it is planned to backfill the open pit with cemented and solidified tailings. In this paper, the numerical simulation method is used to simulate the interaction between open pit solidification backfilling and underground mining. The results show that there is basically no interaction between open pit solidification backfilling and underground mining. The research results can provide reference for mines under similar mining conditions.

Abstract:Backfilling treatment of open pit is an effective way to realize ecological treatment of open pit mining area and solve the problem of tailing surface accumulation. Based on the engineering background of Dagushan Iron Mine of Angang Group, this paper preliminically determined the range of parameters such as the concentration of slurry ratio and the ratio of ash and sand through preliminary tests, and conducted a comprehensive test on the basis of this range. The uniaxial compressive strength and shear strength parameters of the cemented specimens were measured. Based on the comprehensive test results, the influences of lime sand ratio, slurry concentration, curing age and other factors on the uniaxial compressive strength and shear strength parameters of the cemented body are obtained, which provides a reliable reference for the subsequent backfilling treatment of open pit.

Abstract:The study of the influence of dynamic disturbance of mining blasting on the stability of roadway is an important aspect of mine safety production. In order to study the dynamic response rules of the reserved roadway in the backfill under different disturbances, a three-dimensional numerical model for the dynamic stability analysis of roadway was established by 3DEC software and numerical simulation analysis was carried out, and the deformation characteristics and stress field distribution characteristics around roadway under dynamic blasting load were analyzed. The results show that blasting changes the range of compressive stress and tensile stress around the roadway to some extent. Using the reserved roadway mining mode of steel mesh + steel wire rope can greatly weaken the dynamic disturbance of blasting outside the roadway and improve the stability of the roadway.

Abstract:In order to reveal the main influencing factors of gas migration in surface wells under the influence of mining and realize efficient gas extraction in surface wells, the stress and seepage equations of coal body were deduced, based on the multi-physical field coupling mathematical model of coal body containing gas, and then the relationship between the porosity and permeability and the parameters such as strain and gas pressure was obtained. Finally, with a mine in Shanxi Province as the engineering background, COMSOL Multiphysics software was used to simulate the surface well gas extraction practice,the initial and boundary conditions of numerical simulation are established, and the influences of different in-situ stress conditions, different initial permeability and different initial gas pressure on drilling production and efficiency were analyzed. The result shows: The gas extraction rate and quantity of surface drilling are obviously affected by ground stress, gas pressure and permeability, among which permeability is the decisive parameter, but permeability is mainly affected by ground stress. Under certain in-situ stress conditions, porosity and permeability decrease first and then increase with the increase of extraction time, and there is a critical residual gas pressure point; Initial permeability has an obvious influence on surface well gas extraction. The larger the initial value is, the more significant the gas pressure drops, and the higher the extraction rate and quantity simultaneously. Therefore, increasing the initial permeability of coal seam can be regarded as a way to realize efficient extraction in surface wells. The field test of mining surface well shows that the extraction concentration and pure quantity increase step by step under the influence of full mining pressure relief and permeability increase, which greatly improves the extraction efficiency of surface well.

Abstract:In deep environment, rock damage and creep deformation will occur under three-dimensional stress for a long time. In order to reasonably characterize the creep deformation process of rock, a fractional derivative modeling method is adopted to improve the Newton clay pot into a fractional clay pot. At the same time, considering the damage evolution state of rock during the long aging process, exponential damage variables are introduced into the physical parameters. A fractional-order creep constitutive model is established and extended to three-dimensional form. Finally, the validity is verified by using the experimental data of sandstone. The results show that the creep experiment of sandstone has obvious three-stage creep deformation characteristics, and the established fractional-order creep model considering damage process has fewer physical parameters, which can well describe the creep deformation process of rock in deep three-dimensional stress environment, and verify the validity of the model.

Abstract:In order to solve the dust control problem caused by the increase of dust production in coal mine, based on the status quo and existing problems of the comprehensive dust control system of Donghuantuo mine, the comprehensive dust control concept of mine was sorted out, and the influence of dust removal fan, dust collector and wall duct on the dust concentration of working face was compared by using technical means such as field measurement, numerical simulation and experimental research. Further analyze the current situation of dust treatment of fully mechanized mining face, test the dust distribution in different locations and different processes, analyze the dust movement law and dust control system construction of comprehensive mining face, the dust migration law and dust control system construction of fully mechanized mining face, and the safety culture construction of mine comprehensive dust control system.

Abstract:In order to explore the characteristics of local coal rib spalling in large mining height working face and put forward effective measures to control the stability of coal wall, the characteristics of coal rib spalling in the advancing process of large mining height working face were studied through the statistics of the shape of coal rib spalling in working face and 3DEC numerical simulation, and the measures to control the stability of coal wall in large mining height working face were put forward. The results show that the main forms of coal wall spalling in large mining height face are the overall failure of coal wall induced by coal shear slip, shear slip failure, tensile fracture failure, fracturing failure and plate crack failure, and the frequency of each spalling form is smaller in turn. Under the influence of mining, the larger horizontal displacement distribution and spalling range of coal wall are mainly in the middle and upper part of the working face, accounting for about 3/4 of the mining height, spreading from the upper part to the middle and lower part, and finally running through the whole coal wall and extending to the depth of the coal wall. Finally, the spalling of coal wall with large mining height presents the characteristics of large degree, wide range and large depth. In addition, 12 main influencing factors of coal rib spalling in large mining height face are summarized and analyzed, and the control measures of coal wall stability in large mining height face are put forward from the perspective of direct controllable factors and indirect controllable factors respectively.

Abstract:In order to accurately grasp the evolution and distribution law of overlying strata fissures in extra-thick coal seam mining in Jingyuan mining area, and provide a basis for the layout of gas extraction system in the course of mining, the north 1103 working face of Weijiadi mine was taken as an experimental prototype, by means of combining physical similarity simulation with UDEC numerical simulation, the mining test of working face is carried out, and the law of cyclic weighting of overlying strata in extra-thick coal seam is calculated, and the variation law of surrounding rock stress during mining is analyzed, the evolution and distribution law of mining fracture in extra-thick coal seam is studied. The results show that the fracture zone and the collapse zone stop developing upward at the last periodic weighting, the heights are 39.1m and 127.9m respectively, and the stress distribution in the stress concentration zone of the surrounding rock is axisymmetric, the distribution range is 8.94MPa something 19.8MPa, the stress distribution in the pressure relief area is parabola, and the distribution range is 0.22MPa something 1.46MPa. The height of the pressure relief area and the height of the maximum displacement area gradually increase with the increase of coal seam mining height, and the increase trend of the height of the pressure relief area tends to be slow, the variation range is 70.4m something 81.2m, the height ofmaximum displacement area is 52.4m something 74.8m, its width decreases with the increase of mining height, and the variation range is 102.3m something 71.6m, the main key stratum has obvious subsidence deformation, no obvious fissure above, fissure surge below, the width of compacted area in goaf decreases and the height increases.

Abstract:The deformation of roadways and stopes in the process of mining is the reflection of multiple factors such as crustal stress, tectonics and rock mass strength. Crustal stress is one of the important influencing factors. Studying the measurement results of original rock stress is helpful to comprehensively understand the distribution of crustal stress in the whole project area, and provide a basis for engineering design and mining. The method and principle of in-situ stress measurement by relief method are described. The in-situ stress measurement by relief method for two medium stage which the depth are more than 600m in the certain mine, shows that the stress field in the exploration area is dominated by the horizontal stress, and the maximum horizontal principal stress is 14.25~20.17MPa. The intermediate principal stress values were 8.34~11.35MPa, respectively. The minimum principal stress values are 5.67~8.68MPa respectively, which are vertical stresses. The direction of the maximum principal stress in the measuring area is NNE~NEE. The difference between the maximum principal stress and the minimum principal stress in each test section is large gap, and the ratio is about 2.54 on average, which will result in relatively large shear stress. R_c/σ_max is used to calculate the stability of roadway surrounding rock. For medium stage -258m, dacite porphyry and diorite rocks are of low stress and no rock burst. The deformation grade of sericite phyllite is slight. For medium stage -378m, the surrounding rock of dacite porphyry is highly stressed and prone to rock burst; Diorite belongs to low stress, without rock burst; Quartz porphyry is of high stress and medium grade of large deformation; The large deformation grade of sericite phyllite surrounding rock is slight.

Abstract:This article is based on the special project of visual safety monitoring for metal and non-metallic mines. 3D laser scanning technology is used to monitor the safety of the Miyi Wanniangou tailings pond. The reservoir area from January 2021 to December 2022 was scanned and monitored. The results show that the current length of the dry beach is 524.555 meters, the area of the Wanniangou tailings pond has increased by 145000 square meters, and the height of the accumulation dam has increased from 1579.249 meters to 1589.09 meters, with a total increase of 9.841 meters, The dam construction speed is 5.134m/a; Approximately 12.657 million cubic meters of newly added tailings， The stacking rate is 66036500m³/a； The total capacity of the tailings pond is relatively large, and the dam construction and discharge rates are fast. In order to prevent serious consequences caused by dam failure, three limit equilibrium methods were used. The calculation results show that the tailings pond is currently in a stable state.

Abstract:An iron mine tailing with the cobalt content of 0.012% has not been effectively utilized. To investigate the feasibility of cobalt resource recovery, related experimental study was carried out in this paper, focusing on the effects of flotation concentration and slime on cobalt mineral flotation recovery. The study found that desliming and appropriate flotation concentration are beneficial for cobalt mineral flotation recovery. Finally, it was determined to use a cyclone for desliming. Under the condition of a flotation concentration of 25%, butyl xanthate was used as the collector, and a process flow of one coarse, two fine, and one sweep was used to obtain a cobalt concentrate with a grade of 4659.11 ppm and a cobalt recovery rate of 54.41%.

Abstract:Regenerative braking is an important mean to realize energy recovery in the downhill process of electric mining truck. In this study, energy consumption characteristics of mining truck in different driving conditions were studied, driving conditions of electric mining truck and fuel mining truck were collected respectively, driving conditions of mining truck were clustered, energy consumption characteristics of mining truck in different working conditions were studied through data analysis, and energy consumption differences between electric mining truck and traditional fuel oil mining truck were evaluated. The research results show that the electric mining truck can obtain the most braking energy recovery under no-load and heavy-load conditions. Compared to the fuel mining truck, the electric mining truck can effectively reduce the fuel cost by about 83% under the same driving conditions.

Abstract:Green and high-quality development is the background of the development of modern mining. It is necessary to implement the concept of green, safe, efficient and intelligent new mines. Relying on the conditions of the industrial site of a mining to dig and fill in, it has carried out discussions on the supporting structure design scheme for the high-filling slope under the conditions of limited land, and the slope waist construction has carried out a transmission structure for mining truck. The flexible geogrid retaining wall design scheme that can adapt to the uneven settlement of the filling slope is selected. For the two different slopes combination solutions, detailed stability analysis calculations were carried out. The determined design scheme can meet the requirements of engineering conditions, meet the requirements of green, safe, and environmentally friendly, and can provide a reference significance for similar projects.