CHINA MINE ENGINEERING

Abstract:In order to develop a method of determining the optimal angle of planting holes on high steep slopes, four indicators of space utilization, degree of structural surface exposure, water recharge capacity, and anti-evaporation capacity were proposed to determine the optimal angle of planting holes for slope regreening, COMSOL Multiphysics was used to simulate the unsaturated infiltration of porous media and water vapor transport by heat and moisture coupling, and the influence of the change of the angle of planting holes on these four indicators was discussed. In order to verify the simulation results, an experimental site was established at the slope in Yanxiu Garden of Xuzhou Garden Expo Park, and the data of the test holes were monitored, measured and processed for analysis on site. The results show that under the condition of controlling depth of 50cm and diameter of 20cm, the planting hole angle of 40°~60° can ensure high space utilization; in the range of 30°~80°, the larger the angle of planting hole is, the better it is for receiving water recharge by natural rainfall or spraying maintenance, but at the same time, the resistance to evaporation under high temperature and dry conditions is weakened; the angle of the planting hole corresponding to best exposure of the structural surface can be obtained by establishing and calculating the 3D model of the slope and the structural surface. The research results and the optimal angle determination method have good guidance for regreening project.

Abstract:When transferring from open-pit to underground mining, the pillar in the panel area can withstand the load of the overlying rock layer, which has a significant impact on the stability of the rock mass in the mining area. To ensure the safety of underground mining production, this study uses numerical simulation methods to generate a three-dimensional real-scene model based on the image data obtained from drone aerial photography. A three-dimensional mine numerical model is established, and different width strip pillars are arranged between panels. Four types of panel pillars with widths of 20m, 30m, 40m, 34m, and 26m are compared and analyzed for size. By comparing the stress distribution and plastic distribution characteristics of the pillar in the panel area, it was found that as the pillar width increases, the plastic failure distribution area decreases, and the maximum principal stress value decreases. This can effectively protect the stability of the mining area, and the optimal plan with a pillar width of 34m and 26m alternating is obtained. The research results can provide a reference for pillar design under similar mining conditions.

Abstract:Slope instability and failure are significant risks in open-pit mining. As a means of feedback on deformation information and early warning of slope failure, in-situ monitoring is of great significance for predicting slope safety risks. Although slope monitoring technology has made significant progress in recent years, slope monitoring design still faces some bottlenecks, such as reasonable matching of monitoring systems and difficulties in determining warning thresholds. Determine the content of slope monitoring according to relevant regulations for non-coal mines; Combining the mainstream “air sky ground” integrated monitoring technology of multi-source and multi-site safety monitoring for open-pit mine slopes, select safe and economical monitoring methods; Based on some actual monitoring cases of open-pit mining landslides in recent years, the early-warning threshold of slope monitoring design is given by using the four level early-warning system. The research starts from all aspects of slope monitoring and forms a complete set of design methods for open-pit mining slope safety monitoring based on multi-source data fusion.

Abstract:For open-pit to underground mining projects, the protective pillar is a key connecting part of the shallow to deep underground mining. The thickness of the protective pillar not only affects the safety of underground mining, but also affects the economic benefits of the mine. The rationality of its size is extremely important for the stability of the project and the safety of deep mining. An iron mine is a large deep open pit mine, and after the completion of surface mine mining, it will be transferred to underground mining. In this paper, FLAC3D software is used to establish a three-dimensional numerical model in combination with the engineering geological conditions of the iron mine, mining process plan, etc., to simulate and analyze the stability of roof pillars with different thicknesses. The results indicate that the setting of isolation pillars can effectively control the deformation of surrounding rock and the destruction of the goaf, ensure the safe mining of the ore body under the goaf, and determine the optimal thickness of artificial isolation pillars. It has certain reference and reference significance for recycling and safety production of similar mines.

Abstract:In the current intelligent coal mine scenario, the time-series data generated by a large number of coal mine microseismic sensors is growing explosively, which in turn has higher requirements for the existing storage system and performance. There are already instances where HBase, a distributed column family database, can store industrial time-series big data, the existing strategies are still unable to better meet the needs of coal mine microseismic waveform time-series data because they do not consider the feature association of data in specific business scenarios. specific storage requirements. In view of the above problems, based on the distributed storage system HBase, using the characteristics of coal mine microseismic waveform time series data, a coal mine microseismic time series big data storage performance optimization (CM2TS-HBase) based on HBase and Netty is proposed, which is divided into four parts, namely data acquisition layer, data preprocessing layer, data transfer layer, and data storage layer. Among them, the data acquisition layer is divided into offline part and real-time part. The offline part is the historical microseismic time series data files stored in the hard disk of the data center, and the real-time part is the multiple microseismic waveform sensors deployed in a coal mine. The layer performs data buffering; the data preprocessing layer implements alignment, parsing, and serialization operations on files of waveform time series data. According to the characteristics of coal mine microseismic waveform time series data, the HBase data table structure, pre-partition strategy and primary key optimization strategy suitable for microseismic waveform time series data are proposed, which effectively solves the data hot spot problem and data dispersion problem in the data storage process; data transfer layer A data forwarding middleware platform based on Netty and Redis is proposed to provide an asynchronous processing mechanism for the entire storage system, which better solves the problem of high concurrent storage; the data storage layer is based on the distributed database HBase as the underlying storage medium of the storage system. Finally, according to the time-consuming storage of real data sets, it is proved that compared with the native storage method (HBase API) and financial time-series data storage optimization (FT -HBase), CM2TS -HBase has significantly improved the storage performance of coal mine microseismic time-series data.

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 of maximum 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:In order to investigate the mechanical properties of bolts in the process of roadway support, this paper adopts distributed fiber optic sensing technology to monitor the mechanical properties of two bolts of different diameters under the action of axial load respectively, and analyzes the strain law of both of them in the process of axial deformation. The results show that the larger the diameter of the bolt under axial load, the stronger the resistance to elastic deformation at the elastic stage; With the increase of axial load, the strain increment near the neck contraction fracture position of bolt is larger than that at other positions; The distributed optical fiber sensing technology can monitor the stress-strain state of the bolt under axial load in real time, and can judge the specific location of the neck contraction phenomenon when the bolt is broken.

Abstract:To investigate the dynamic tensile mechanical response characteristics of sandstone under impact load, the ? A 50mm split Hopkinson compression rod system was used to conduct dynamic Brazilian splitting disk experiments on sandstone. The research results indicate that the dynamic tensile strength of sandstone under impact load increases with the increase of loading rate, in a quadratic function relationship, and the peak strain of sandstone is negatively correlated with loading rate; In the process of dynamic tensile failure of sandstone, the fragmentation dissipation includes three stages: plastic energy storage stage, plastic deformation energy storage stage, and failure stability stage. Among them, the incident energy, reflected energy, and transmitted energy all increase with the increase of loading rate, showing a linear function relationship (R²≥0.84), and the energy consumption rate shows a quadratic function relationship (R²=0.98). The research results provide reference for the control of coal mine surrounding rocks.

Abstract:Natural caving method mines are generally thick ore bodies, the horizontal area of the bottom pulling is large, the vein penetration is long, if the cutting along the vein is not used, it is easy to cause the horizontal loosening of the bottom pulling ore transportation distance is long, ventilation is difficult. Under the superposition of supporting pressure and lateral bearing pressure, a high-stress concentration area is formed at the intersection of the bottom and the roadway along the vein, which has a great influence on the blasting quality of the bottom pull. In order to improve the blasting quality of the bottom over the vein and protect the stability of the bottom structure, this paper analyzes whether a mine has a cutting shaft and has a cutting shaft along the vein, and determines that the blasting effect of the cutting well along the vein under high stress is better, which can effectively change the minimum resistance line of blasting, increase the blasting free surface, reduce the single consumption of explosives, improve the charge coefficient, improve the quality of the bottom blasting along the vein, and effectively protect the stability of the bottom structure.

Abstract:The characteristic of a certain metal ore body is a gently inclined and thick ore body with shallow burial depth, developed rock joints and fissures, and the presence of roads and buildings on the surface. Underground mining may have an impact on the surface buildings and roads in the mining area. To solve the above problems, this article selects the mining schemes of large-diameter deep hole lateral collapse and deep hole open pit method in chassis trenches. FLAC3D software is used to simulate and analyze the deformation laws of the mining surface movement and settlement mechanism caused by filling mining, and the differences in surface movement and deformation under filling and unfilled conditions are compared and analyzed. Research has shown that the filling mining method can make the surface rock move towards continuous deformation and uniform subsidence, effectively enhancing the safety protection level of mining surface structures, and has feasibility.

Abstract:In response to the problem of large deformation of surrounding rock under the original support conditions of the return air roadway in the 1303 working face, which cannot meet the demand for efficient coal extraction in the mining face, it is proposed to comprehensively use technical means such as on-site measurement, drilling observation, and numerical simulation to analyze the causes of large deformation of surrounding rock, and provide an optimization plan for rock support. The analysis found that the main reasons for the large deformation of the surrounding rock in the 1303 return air roadway are the looseness of the surrounding rock, the expansion when encountering water, the lateral stress in the adjacent goaf, the water pouring in the surrounding rock, and the unreasonable original support parameters. Therefore, two optimization schemes, namely anchor rod+anchor cable+metal mesh, and anchor rod+anchor cable+metal mesh+grouting, are proposed for this purpose. Through numerical simulation analysis, the optimal scheme is to use anchor rod+anchor cable+metal mesh+grouting, and specific technical parameters for tunnel support are provided. After engineering application, the maximum convergence values of the top, bottom, and side of the return air roadway were 182mm and 63mm, respectively. The deformation values decreased by 72.7% and 85.8% compared to before support optimization, indicating that the optimized support scheme effectively controlled the deformation of the surrounding rock of the return air roadway.

Abstract:Organic polymer flocculant has been used for many years in Tonglushan mine, but because there are so many manufacturers and product variety for flocculant and the purchase price is also different on the market at present, which has increased the difficulty of flocculant selection and procurement and application. In order to screen out the suitable flocculant type for total tailing settlement of Tonglushan mine and reduce the cost of flocculant, the solubility test in water and settlement comparison test has been carried out between four kinds of best-selling brands polymer flocculants on the market and flocculants used in production site, then the production cost has been calculated on the basis of the experimental research in this paper. The research results show that under the dosage of 18g/t, the tailing settlement speed for the five kinds of flocculants from fast to slow is arranged in the following order: YD-6, A556, A345, JC186, 3660DF. And when the settlement speed is faster, the concentration of settlement layer is higher. Among which the best dosage for three kinds of flocculants at A345, A556, YD-6 with better settlement effect are 21g/t, 18g/t, 18g/t, respectively. Finally, considering the test effect and production cost consumption of flocculant, the flocculant of YD-6 is recommended, and the production dosage is 18g/t.

Abstract:The layout of wide alleys in mines can cause waste of working face resources. To solve the problems of coal waste and gas emissions caused by the layout of wide tunnels in high gas mines, this article proposes a technical solution for constructing concrete walls into tunnels. By using numerical simulation methods, the stress distribution law of surrounding rock in different widths of concrete wall tunnels was analyzed, and the material ratio for constructing concrete walls using flexible formwork pumping technology was studied. The optimal height of concrete wall tunnels was revealed, and the concrete wall tunnel technology was optimized based on actual situations. The results indicate that when the width of the concrete wall is 1.6m, the stress concentration of the isolation wall is the smallest, it has good bearing capacity, and is less prone to plastic failure and instability under the influence of mining. The combined application of flexible formwork pumping technology to construct concrete walls and support technology can effectively maintain the deformation of surrounding rocks. This study has achieved pillar free mining in high gas mines, providing a certain theoretical basis and phenomenon basis for maintaining the stability of tunnel surrounding rock.

Abstract:The main coal seam of Wanfeng Mine has soft coal quality, poor permeability and uneven gas deposit, which makes gas extraction difficult and ineffective. In order to find out a complete set of technology to improve the concentration of gas extraction and further increase the gas extraction rate, we put forward the optimization technical measures such as “two plugging, one injection and one row” sealing hole, “DN150 confluence” connecting holes, and water discharge from the gas extraction branch pipe, etc., and carried out on-site experiments to get the optimization technical measures under the conditions of different extraction concentration and effect. Field tests were carried out to obtain the concentration and effect of extraction under different conditions of optimized technical measures. The results show that: the concentration of the new “two plugs, one injection and one discharge” sealing holes is generally above 70%, and the decay rate of the gas concentration is greatly reduced; after draining the gas extraction stub pipe, the concentration of the stub pipe is generally above and below 35%, and it is gradually improved with the increase of the continuous extraction holes. In order to provide a reference for safe and efficient coal mining at the face.