CHINA MINE ENGINEERING

Abstract:The orepass-crushing system is a critical large chamber in underground metal mines during construction and production phases. Temporary and permanent support methods are essential to maintaining the stability of the chamber during excavation and service periods. Taking the excavation of a large crushing chamber in a Serbian copper mine as an example, the excavation process and support methods were determined based on geological characteristics and operating conditions. Support parameters, such as rock bolts and prestressed long anchors, were calculated using reinforced arch theories. The results show that a single-side pilot drift with positive step layered excavation ensures stability during the excavation of large chambers in poor rock conditions. For the upper-layer arch, the “pilot drift-extension brushing” three-step excavation reduces the vertical displacement of the roof and horizontal displacement of the sidewalls by 27.9% and 35.7%, respectively, compared to one-time full-section excavation. Under combined temporary support (bolts, mesh, shotcrete, and anchors) and permanent support (reinforced concrete), the stress arch in the roof and tensile stress in the sidewalls of the crushing chamber were significantly reduced. The displacement of surrounding rock and the maximum depth of the plastic zone were also effectively minimized, ensuring safety during both the excavation and service periods of the crushing chamber.

Abstract:Reasonable stope structure parameters are of great significance to safe and economic extraction in mines. A copper iron ore was mined by sublevel open stoping followed by filling mining method. In this paper, the numerical simulation method was used to conduct a comparative study of different sublevel heights (12m and 17.5m), revealing the evolution laws of stress, displacement and plastic zone distribution of the stope under different sublevel heights. It can provide reference for mines under similar mining conditions.

Abstract:Under the high stress mining environment in the deep part, the internal joints and fissures of the rock mass develop, and the degree of fragmentation intensifies, resulting in a decrease in the bearing capacity of the surrounding rock of the roadway and prominent deformation and damage problems. This article uses a discrete fracture network (DFN) to construct a tunnel model with a certain fragmentation structure, simulating the excavation process of tunnels with burial depths of 500m, 1000m, 1500m, 2000m, and2500m respectively. Combined with the theory of stress mechanics of surrounding rock in circular tunnels, the bearing structure characteristics of surrounding rock in tunnels under high stress environments are studied. Based on the stress distribution law of surrounding rock in tunnels with different burial depths, the bearing structure of surrounding rock was divided into zones, and the relationship between tunnel burial depth and plastic zone expansion was obtained, revealing the fracture characteristics of fractured rock mass under high stress. The research results can provide reference for the design of surrounding rock support in tunnels under similar mining conditions.

Abstract:This article takes the 1811 coal mining face in the southwest region as the engineering background. Through theoretical analysis, numerical simulation, and on-site industrial testing, a mechanical model of the surrounding rock structure of the inclined coal seam along the goaf was established. The deformation and failure laws of the surrounding rock of the inclined coal seam along the goaf were studied under different factors, and flexible support technology was proposed accordingly, which was applied on site. 〖JP2〗Research has shown that increasing the strength parameters of the coal rock interface or enhancing the support strength is the most effective way to narrow the limit equilibrium zone. As the cutting angle, coal seam inclination angle, height width difference of the roadway, and coal seam burial depth increase, the deformation and damage of the surrounding rock of the roadway become more significant, the shrinkage rate of the roadway further increases, and the degree of basic roof fracture significantly increases. As the basic roof thickness increases, the degree of deformation and damage of the surrounding rock in the tunnel decreases. The three stages of vertical stress on the coal wall side of the roadway and the evolution of overlying rock in the roadway have been divided, and the roadway can be judged by monitoring the stress changes of the coal wall to achieve pre control of surrounding rock disasters in the roadway. The research results can provide reference for controlling the surrounding rock of the roadway along the goaf of gently inclined coal seams in the southwest region.

Abstract:This article takes the close range coal seam mining conditions of a coal mine in Inner Mongolia as the research background. This study was conducted on the stress and state characteristics of the rock mass of the main roadway coal pillar under the influence of stress transmission from the upper coal pillar, and the stress law of the coal pillar under different coal pillar widths was analyzed. The research results indicate that under the conditions of close range coal seam mining, the concentrated stress of the upper coal pillar will be transmitted to the lower coal pillar, causing stress superposition in the lower coal pillar. At the same time, it will significantly increase the range of the fracture zone and plastic zone in the coal body. As the width of the coal pillar decreases, the degree of stress concentration in the coal pillar also further increases. The constructed neural network model can effectively evaluate the stress and state of coal pillars in close range coal seam mining.

Abstract:The sources of water inrush were analyzed using the tunnel water inflow prediction method and C14 tracing technique. Based on the Q-value assessment of the surrounding rock mass and unsupported span analysis, three initial mining method schemes were selected: pre-cut top medium-deep hole room-and-pillar subsequent filling, mechanized upward horizontal stratified filling, and mechanized upward drift filling. The disturbance ranges of each mining method were analyzed through FLAC3D numerical simulations. Ultimately, the mining method was recommended through a comprehensive comparison of the technical, economic, and safety aspects of the schemes. The results indicate that the primary source of water inrush in the deposit is the karst confined aquifer in the floor, with a maximum water inrush rate reaching 35000m3/d. The disturbance range of mechanized up-approach filling method is the smallest, and the disturbance range is 3~4m. Considering the current grouting reinforcement range of 15 meters, the thickness requirements for the safety isolation layer in the aquatic environment, and the technical and economic indicators of the schemes, the mechanized upward drift filling method was preferentially recommended. Field industrial tests demonstrated that implementing multi-sequence advanced grouting reinforcement in the mining area significantly reduced the water inrush in the stope. The stope achieved a comprehensive mining capacity of 110t/d, with a loss rate of 6% and a dilution rate of 4%. This study provides technical support for the safe and efficient mining of gently inclined orebodies in water-rich environments.

Abstract:In order to optimize the gas treatment of high gas mines, this paper takes the S1205 working face of Yuwu Coal Industry as the research object, and uses numerical simulation methods to study the gas concentration distribution under four ventilation modes: U-shaped, W-type, U+ high-pumping type and Y-type. The research methods include the establishment of numerical models to determine the key parameters such as fragmentation coefficient, permeability and gas mass source phase of mining fractured coal and rock, and the simulation analysis is carried out by using FLUENT software. The simulation results show that the gas concentration in the upper corner exceeds 1% and 9.3% respectively under the U-shaped and W-shaped ventilation modes, which cannot meet the safety requirements. In contrast, the U+ high-pumping ventilation mode effectively reduces the gas concentration when the negative pressure of the high-pumping roadway is 8KPa, in which the gas concentration of the return air roadway is kept below 0.5%, and the gas concentration in the upper corner is reduced to less than 0.8%. Further analysis of the influence of the high extraction roadway layer on the gas treatment effect shows that when the high extraction roadway layer is between 15m and 20m, the gas concentration of the return air roadway can be better controlled. Although the Y-type ventilation method is theoretically better than the U+ high-pumping type, it is less economical.

Abstract:In order to study the influence of five factors, namely, initial gas pressure, coal seam porosity, drilling diameter, negative pressure and initial permeability, on the effective radius of gas extraction under the drilling, numerical simulation was constructed by COMSOL, and orthogonal experiments and analysis of polarity were used to explore the influence of the factors, and the equations were obtained by using linear regression analysis of the SPSS software. The results show that the Initial permeability has the greatest influence on the effective radius of gas extraction; the degree of influence of the extreme variance analysis is, in order of magnitude, the initial permeability, drilling diameter, the negative extraction pressure, the porosity, the initial gas pressure; the optimal combination of factor levels with the largest effective extraction radius is when the initial gas pressure is 1.2MPa, the porosity is 0.08, the drilling diameter is 94mm, the negative extraction pressure is 20kPa and the initial permeability is 1×10^-15m²; the coefficient of determination R²=90.6% in the multiple linear regression equation is a good fit.

Abstract:In this study, the numerical model of the drill hole is constructed, and the depth of burial is used to characterize the overall stress level of the borehole, to investigate the stress distribution characteristics around the borehole under different burial depths, to elucidate the time-varying characteristics and distribution of the displacement around the borehole, and to reveal the influence of the depth of burial on the development of the cracks around the borehole. The results show that the stress concentration phenomenon occurs after the stress field of the coal around the drill hole is adjusted. With the increase of burial depth, the stress around the drill hole gradually increases, and the range of stress concentration area is increasing. The deformation of the coal body around the hole has a certain direction, and the deformation of the coal body will be larger along the straight line direction, and the perpendicular direction to this straight line will have a smaller deformation. With the increase of burial depth, the deformation of coal around the borehole increases. There is a certain correspondence between the development of fissures and the deformation around the coal. With the increase of burial depth, the development of fractures is gradually obvious, and the distribution is characterized by concentration in the middle and dispersion around.

Abstract:In order to achieve stable control of filling slurry quality concentration based on electrical signal feedback, a study was conducted on the characterization of filling quality concentration based on electrical signals during the stirring process. Experiments on the mixing characteristics of full tailings filling slurry with different mass concentrations was designed and conducted, collect electrical signal data such as torque, power, current during the mixing process, and the original data was pre-treated to reduce noise using Kalman filtering method. The experimental result shows that the three types of mixing electrical signals present a significant positive correlation with the change of full tailings filling slurry mass concentration. When the slurry mass concentration increases from 68% to 76%, the values of torque, power, and current signals increase by 22%, 29%, and 20%, respectively, For every 1% increasing, the values of the three electrical signals show significant differences; Based on this, a study was conducted on the evolution law of stirring electrical signals with the mass concentration of slurry, revealing the inherent relationship between the mass concentration of filler slurry and stirring electrical signals, the sudden and continuous characteristics of stirring electrical signals near the critical concentration of slurry were discovered, and a related model of stirring electrical signals and slurry mass concentration was proposed and was analyzed and studied in depth, finally, the characterization method, model, and parameters of filler slurry concentration based on stirring process electrical signals were clarified, laying the foundation for achieving stable control technology of filler slurry mass concentration through electrical signal feedback during the stirring process.

Abstract:This article conducts experimental research on a certain mines tailings as material, by analyzing the physicochemical characteristics of the tailings in the mine, the particle size distribution characteristics of the tailings were obtained and determined that the tailings of the mine are superfine tailings with good gradation but unstable continuity. Through flocculants selection experiments, it was found that the 645S flocculants has the best effect on settling tailings; through tailings flocculation settling experiments, it was found that the optimal flocculants consumption for tailings with concentrations of 7.5%, 10%, and 12.5% were 40g/t, 40g/t, and 60g/t, when the tailings concentration was 15%, it did not meet production requirements; through multiple linear regression analysis, regression equations with good statistical significance were obtained for the concentration of tailings, unit consumption of flocculants, and average settlement velocity within 180 seconds; Based on the comprehensive experimental results, under the optimal settlement conditions, the higher the concentration of tailings, the lower the height of the clarification layer, the average settlement speed, and the concentration of compacted layer treatment, that is, the worse the settlement effect of tailings. Athough the mass concentration of the compacted layer is higher after 24 hours of natural settlement compared to the addition of flocculants, the required time for natural settlement is longer and cannot meet production needs. Therefore, adding an appropriate amount of flocculants to promote tailings settlement is a necessary measure in the mining filling process.

Abstract:This article proposes a comprehensive evaluation method for the stability of open-pit mining slope based on finite element method. Taking a certain open-pit mining site as the research object, a geometric model of the slope was constructed, reasonable rock and soil mechanics parameters were selected, and the stress, displacement, and safety factor of the slope were numerically simulated and analyzed using finite element method. Under various load combinations, the safety factor of the slope was calculated and the instability modes of different profiles were identified. The research results indicate that this method can accurately reflect the mechanical behavior of slopes under self weight, blasting vibration, and seismic loads, which helps to improve the safety and operational efficiency of mining sites.

Abstract:In order to reduce the degree of damage to the ecological environment during the development of mineral resources, and to realize the coordination of resource development and environmental protection, the establishment of a resource and environmental balance system is the only way to promote the high-quality green development of China’s mining enterprises. As an indispensable part of the green mine resources and environmental balance system, it is urgent to conduct an in-depth study of the water balance. This paper analyzes the water consumption and water extraction of mines, clarifies the definition of water balance, and establishes the relationship between water balance on this basis, proposes the corresponding formula for calculating the water balance, and at the same time, details the components, and puts forward suggestions and ideas to help realize and optimize the water balance, which will help China’s green mine to build comprehensively, and promote the transformation and upgrading of China’s mining enterprises.