矿业科学学报

Subsection Kalman filter model for mining subsidence monitoring data processing

Hao Dengcheng, Wang Guorui, Li Peixian, Shen Jiaqi, Cao Yuxi, Yang Zhonghui

2021, 6(4): 371-378. doi: 10.19606/j.cnki.jmst.2021.04.001

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Abstract:
Kalman filtering is used to filter GNSS mining subsidence monitoring data in order to solve the problems of long period and high frequency GNSS mining subsidence monitoring data that are greatly affected by the external environment, high data interference noise and low data reliability. Firstly, the regression analysis method is adopted to automatically divide the monitoring data into three parts: the initial stage, the active stage and the decline stage. The subsidence in the initial stage and the decline stage is relatively stable, and the subsidence data is filtered by the standard Kalman filtering model. The add correction kalman filter model was constructed to deal with the data in the active stage of rapid subsidence change. The filter program was established by Python language, and the monitoring data of five-year and hourly interval sampling rate in a mining area in Ningxia were calculated and analyzed. The results showed that the process curve of different kalman filtering results in different stages was consistent with the measured results, and the filtering effect was good. The add correction kalman filter model can effectively process the monitoring data of mining area with large subsidence variation. The method constructed in this paper can effectively reduce the impact of data fluctuation on the subsidence result and improve the reliability of monitoring data. The research results provide a scientific basis for long-term and high-frequency settlement monitoring data processing.

Fracture characteristics of the 8th member of Shihezi formation in Linxing Area and its influence on fracturing effect

Li Jianhong, Wang Yanbin

2021, 6(4): 379-388. doi: 10.19606/j.cnki.jmst.2021.04.002

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Abstract:
In order to study the influence of natural fractures on fracturing effect of the 8th member of Shihezi formation in Linxing area, the characteristics of natural fractures in Linxing area are described based on field joint observation and imaging logging data.At the same time, the micro seismic dynamic monitoring method is used to monitor the process of the formation of the fracturing fractures in the 8th member of Shihezi formation in Linxing area.The results show that: ① The natural fractures of 8th member of Shihezi formation in Linxing area are mainly concentrated shear joints with large dip angle, but the total number of natural fractures is less, and the dominant directions of joint are NNW, NWW, NNE and NEE. ② The fracturing effect of crossing control type is the worst, the communication type is better, and the capture type is the best. Smaller approach angle and horizontal principal stress difference are beneficial to the opening of natural fractures. When the level of horizontal principal stress difference in the fracturing area is higher, It's better to adopt a smaller approach angle for fracturing, and this type control of fracturing is communication. When the level of horizontal principal stress difference in the fracturing area is smaller. It's better to adopt a bigger approach angle for fracturing, and this type control of fracturing is capture control type. The results provide a theoretical basis for hydraulic fracturing scheme design of tight sandstone.

The influence of receptor interval and shot interval on the detection of collapse column

Liu Jiahao, Zhu Guowei

2021, 6(4): 389-396. doi: 10.19606/j.cnki.jmst.2021.04.003

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Abstract:
Based on the geological characteristics and the seismic wave propagation characteristics of the collapse column, a collapse column model is constructed. Considering the change of single factor variation and the acoustic equation used to simulate the effect of different receptor interval and shot interval on the collapse column. Interpretation of the collapsed column fracture boundary is carried out by using the reflected wave amplitude changes of the offset profile and combined with seismic attribute analysis and manual interpretation. The detection accuracy is judged by the average deviation of the horizontal resolution of the collapsed column as an index. And the interpretation error of the diameter of the collapsed column is analyzed by ray tracing method. The results show, that the small receptor spacing is beneficial to the exploration of the collapse column, and when the receptor interval is 5 meters and the shot interval is 40 meters, it is favorable to the exploration of the collapse column model.

Study on 3D modeling method and reinforcement scheme of large and complex open-pit mine

Tao Zhigang, Ren Shulin, Pang Shihui, Xu Haotian, He Manchao

2021, 6(4): 397-408. doi: 10.19606/j.cnki.jmst.2021.04.004

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Abstract:
Large-scale topping deformation occurred in the southwest stope of Changshanhao Open-pit Gold Mine in Inner Mongolia.Through systematic investigation of the engineering geological conditions and rock mass structure types, the deformation characteristics and failure mechanism of the stope are studied in depth.Taking this project as an example, the 3DMine-FLAC^3D large-scale complex geological body high-precision coupling modeling method and modeling process are introduced in detail.Based on this, a slope reinforcement scheme with constant resistance and large deformation anchor cable is proposed, and a numerical simulation method is used to make a comparative study with the original support scheme.The research results show that the geological structure of the southwest stope is complex.Faults and joints are developed.The rock mass in the toppling area is mainly slate and schist with low bending strength, and small deformation anchor cables are used in the supporting structure, which cannot resist large slope deformation.The combined effect of these factors leads to the occurrence of dumping instability.The reinforcement scheme to constant-resistance and large-deformation anchor cables can effectively control the slope deformation and a better support effect is obtained.

Calculation of direct roof subsidence of retracement channel and analysis of its influencing factors

Wang Shushuai, Wang Zhiqiang, Huang Xin, Su Zehua

2021, 6(4): 409-417. doi: 10.19606/j.cnki.jmst.2021.04.005

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Abstract:
The direct roof subsidence of retracement channel is of utmost importanie to the withdrawal of equipment in the final mining stage.Based on the basic roof fracture position, a mechanical model of the direct roof deflection of the withdrawal channel after penetration was established.The expression of the supporting stress was simplified to the n-th parabolic function of x fitted to it.The value of n varies with the fracture position, the expression of the direct roof subsidence at the center line of the roof of the retreat channel was derived.The basic roof fracture position d of 312 working face was about 12 m, at this time n was taken as 4, and the direct roof subsidence was about 105 mm.On the basis of theoretical calculations, the factors affecting the direct roof subsidence were analyzed.The results showed: The direct roof subsidence increases with the increase of the basic roof fracture location, coal seam depth, stress concentration coefficient and the span of the retreat channel, and decreases with the increase of the direct roof thickness and elastic modulus.The influence of other factors is not significant.Under the condition of ensuring the equipment withdrawal space, the span of the withdrawal channel should be reduced as much as possible to control the direct subsidence of the withdrawal channel.

Theoretical model of water spontaneous imbibition of sandstone considering microscopic pore geometry

Dong Chuanlong, Teng Teng, Li Zhihu, Zhang Wentao

2021, 6(4): 418-428. doi: 10.19606/j.cnki.jmst.2021.04.006

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Abstract:
In order to study the influence mechanism of micro pore geometry of sedimentary rock on its water absorption characteristics, based on Hagen-Poiseuille equation, Laplace-Young equation and fractal geometry theory, the capillary water absorption models which is respectively represented by average and fractal geometry are established by taking into account three geometric characteristics of pore section shape, pore size distribution and tortuous pore space.Compared with the existing model, the applicability and validity of representative model are verified by using existing experimental data.Finally, the sensitivity of geometric parameters influencing water absorption characteristics of pore structure is analyzed in detail.The results show that the parameters of water absorption characteristics are related to the pore geometry shape, tortuous fluid channel, free porosity and maximum pore size, whereas the more irregular the pore geometry and the more tortuous the connected pore channel, the stronger the heterogeneity and anisotropy of pore structure, and the weaker the water absorption.The physical meaning of equivalent average pore diameter is not clear in the model represented by average geometry, and the calculation result is larger than the measured values when average space pore size is directly brought into the model, while the physical meaning of parameters is clear in the model represented by fractal geometry, and the results close to measured values can be obtained; the proposed models have strong applicability for the pore structure with weak 3D pore connectivity and pore roar characteristics, and compared with the complicated IFU model and BEA model, similar or even more accurate theoretical predicted results can be obtained based on the simplified models.

Construction and optimization of lignite molecular structure model

Zhu Hongqing, He Xin, Huo Yujia, Xie Yuyi, Wang Wei, Fang Shuhao

2021, 6(4): 429-437. doi: 10.19606/j.cnki.jmst.2021.04.007

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Abstract:
In view of the current situation that there are many but no uniform coal molecular modeling methods, this paper explores the structuve of lignite macromolecules and optimizes them from a microscopic perspective by selecting physical methods that have less impact on molecular structure.A relatively simple coal macromolecule modeling method was put forward.Based on the experimental methods of elemental analysis, ¹³C-NMR and XPS, molecular dynamics simulation software method was used to analyze and study lignite and build molecular structure models.The results show that the aromatic structure of lignite macromolecules is mostly pentaphenyl.The fat carbon structure is mostly methylene and methine, and the alkane chain is mostly cycloalkanes.Oxygen atoms are mostly ether bond oxygen, followed by carboxyl oxygen and carbonyl oxygen.Nitrogen atom exist in the form of Pyridinic nitrogen N-6.After the optimization, the structure of the coal molecular model is more compact and the energy is obviously reduced.As the main component of the non-bonding potential energy and the main factor to maintain the stability of the coal molecular structure, the van der Waals potential energy has the most obvious change.In order to construct coal molecular cell, periodic boundary conditions were added.According to the energy variation, the cell density was 1.2 g/cm³ and the total energy was 1 140.624 kJ/mol, which was basically consistent with the actual situation and verified the effectiveness of the modeling method.This study provides a method for the direct understanding of the macromolecular structure of coal, and is of great significance for the mechanism research and prevention of coal and gas outburst, coal spontaneous combustion and other disasters.

Experimental study on the displacement evolution of rock interface friction slip based on crack

Liu Yan, Yang Xiaobin, Wang Yang, Pei Yanyu

2021, 6(4): 438-444. doi: 10.19606/j.cnki.jmst.2021.04.008

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Abstract:
To study the further evolution characteristics of the fracture plane or structural plane after rock failure, the granite was chosen and prepared as double penetration crack samples, and the friction sliding tests were conducted using twin-shear model.During the tests, the CCD camera was used to record the speckle images, and the digital speckle method was used to analyze the evolution characteristics of horizontal displacement field, vertical displacement and horizontal displacement in the process of friction sliding.The results show that: ① The major role in displacement evolution has changed from confining pressure to a combination of confining pressure and shear stress at the stage of slow growth in shear stress.The displacement evolution is dominated by shear stress at the stage of linear growth in shear stress.The increase and decrease of interface occlusal degree and horizontal alternate displacement can be used as precursors of rock interface friction slip.② The appearance and disappearance of the flow around the horizontal displacement field are the precursors of the local and global slip of the specimen, respectively.③ The relationship between confining pressure and shear stress is characterized by the central contour inclination in the nephogram of displacement field, so it can also be used as precursors of partial and global slip of the specimen.

Mathematical model and numerical solution of constant pressure adsorption of gas in coal particles

Xu Hao, Qin Yueping, Wu Fan, Liu Jia, Chu Xiangyu, Liu Xiaowei

2021, 6(4): 445-452. doi: 10.19606/j.cnki.jmst.2021.04.009

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Abstract:
In order to study the flow mechanism of gas in coal particles, four groups of constant pressure adsorption experiments were carried out at different initial pressures, and the experimental data of cumulative gas adsorption volume content with time were extracted. Based on Darcy theory driven by pressure gradient and new diffusion model driven by the density gradient of free gas, two kinds of mathematical models of gas adsorption at constant pressure were established, and the adsorption process was numerically solved by VB program code, and the simulation data of cumulative adsorption volume content inside coal particles were obtained. By comparing and analyzing the two kinds of simulation results with the experimental data, it is found that numerical calculation results are consistent with the experimental data, thus verifying the accuracy of the numerical simulation. In addition, the key proportional coefficients in the two models with the change of pressure are different. The permeability coefficient is negatively correlated with the pressure, and the microchannel diffusion coefficient does not change with the pressure. It is concluded that the diffusion model driven by the density gradient of free gas is more suitable to describe the gas migration law in coal particles than Darcy's law and Fick's law.

Simulation study on influencing factors of coal wall sudden extrusion in heading face

Wei Chengmin, Li Lu, Wang Qifei

2021, 6(4): 453-461. doi: 10.19606/j.cnki.jmst.2021.04.010

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Abstract:
A three-dimensional numerical model of heading face was established based on Guoerzhuang Coal Mine in Handan, Hebei Province. The effects of different coal seam depths, driving speed and coal mechanical strength on the coal wall sudden extrusion are analyzed by using 3DEC discrete element simulation software, and the orthogonal experiment method is used to rank the influencing factors according to the degree of importance. The results show that there is a positive linear correlation between the maximum horizontal displacement of the fixed point on the heading face and the change of the buried depth, and the direction of the coal wall extrusion displacement is close to the central axis of the roadway, and the horizontal displacement is obviously larger than the vertical displacement. Under the condition of the buried depth of 600 to 1 000 meters, the width of stress concentration area of working face is about 10 meters, and the position of the stress peak is about 5 meters from the working face. The factors affecting the coal wall sudden extrusion in heading face are in the following order: buried depth of coal seam > driving speed > mechanical strength of coal body. The research results provide a reference for further understanding of the coal wall sudden extrusion and preventive measures.

Heat flow characteristics of bituminous coal adsorption and desorption process

Xie Beijing, Ding Hao, Yan Zheng

2021, 6(4): 462-471. doi: 10.19606/j.cnki.jmst.2021.04.011

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Abstract:
The process of coal adsorption and desorption of gas is accompanied by obvious thermal effects, and its variation pattern is of great value for the research of gas hazard prediction techniques such as coal and gas outburst prediction. Using self-designed multiparameter coal adsorption and desorption heat effect test system, we conducted pressure, temperature and heat flow test experiments for CO₂, N₂ and CH₄ gas adsorption and desorption of bituminous coal at 0. 5 MPa, 0. 8 MPa and 1. 1 MPa, and analyzed the characteristics of heat flow changes of bituminous coal during the adsorption and desorption process. The study showed that: (1) during the whole process of adsorption and desorption of bituminous coal specimens, the change of heat flow density on the coal wall is divided into five processes: ①in the evacuation stage, the heat flow increases rapidly and then decreases slowly to 0; ②in the inflation stage, the heat flow is positively correlated with the inflation rate; ③in the adsorption stage, the heat flow is first fast up and then fast down and finally decreases slowly; ④in the deflation stage, the heat flow is positively correlated with the pressure relief rate; ⑤in the desorption stage, it is divided into two stages: the stage of fast down and slow rise. (2) The maximum heat flux values of N₂, CH₄, and CO₂ three gases increase sequentially; for the same gas, the maximum heat flux values under the three gas pressures will increase with the increase of pressure. (3) The theoretical values of heat in the process of adsorption and desorption are always larger than the experimental values, but the overall trend is consistent. (4) The heat flux parameter has the characteristics of inflow and outflow direction vector, which is superior to the temperature index. The heat flux is consistent with the heat transfer change law, which can well characterize the change law of thermal effect of adsorption and desorption of bituminous coal, and provide reference for the research of new index of coal and gas outburst prediction.

Threshold value of numerical index and mining height effect of overburden fracture zone height in Shendong Baode shallow coal seam

Hao Xianjie, Sun Zhuowen, Zhao Yixin, Yang Ke, Zhang Cun, Zhang Qian

2021, 6(4): 472-479. doi: 10.19606/j.cnki.jmst.2021.04.012

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Abstract:
The height of overburden fissure zone is an important index to study the deformation and failure of overburden, but the existing single index can not reflect the fracture degree of surrounding rock in different space parts of stope. Based on 81505 working face of Baode Mine with typical shallow burial conditions in Shendong, the unification of coal sample damage degree and index RFD (Rock Failure Degree) is completed by laboratory experiments, and a similar model and a numerical model are constructed. Based on the index RFD, the maximum destructive depth in numerical simulation is extracted, and the law of development height of overburden mining fissure zone and its variation with mining height are studied by comparing similar simulation results. The results show that the index RFD can well assess the development characteristics of mining fissure zone under typical shallow burial conditions in Shendong. And the development height of fissure zone continuously with the increase of mining height but the growth rate decreases gradually. The research in this paper provides theoretical support and technical basis for distribution and destruction characteristics of fractured zones, occurrence of rock pressure and safe mining.

A study on synthesis of lead-free piezoelectric (K, Na)NbO₃ nanorod arrays

Cheng Liqian, Cheng Hui, Miao Yiying, Sun Yiwen, Zhang Zipei

2021, 6(4): 480-486. doi: 10.19606/j.cnki.jmst.2021.04.013

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Abstract:
As one of the lead-free piezoelectric systems, potassium sodium niobate [(K, Na)NbO₃, abbreviated as KNN] has been a research interest due to its high piezoelectric property, high Curie temperature as well as the tailored phase structures. However, there are still some problems in the study of one dimensional (1D) KNN structures. For instance, the orientation growth of crystals is difficult to be controlled, the piezoelectric properties of the product should be further enhanced. In this paper, the hydrothermal synthesis method was applied to fabricate the 1D KNN structures on the Nb-doped SrTiO₃ (NSTO) substrate. The hydrothermal temperature, Nb₂O₅ concentration and the hydrothermal time were studied, respectively, and the oriented KNN nanorod arrays (NRAs) with high quality were achieved. The results show that the KNN NRAs with single orientation, good crystallinity and high piezoelectric response can be obtained when the hydrothermal temperature is 190 ℃, the Nb₂O₅ concentration is 40 mL/g, and the reaction time is 18 h, respectively.

Adsorption capacity of coal-based activated carbon in advanced treatment of drinking water

Wan Chaoran, Xie Qiang, Liu Deqian, Zhou Yihuan, Wu Haotian, Yang Shuai

2021, 6(4): 487-496. doi: 10.19606/j.cnki.jmst.2021.04.014

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Abstract:
Activated carbon is the core material in the process of advanced treatment of drinking water. Evaluating the adsorption capacity of activated carbon accurately is the basis of its selection in practical applications. In this study, four typical commercial coal-based activated carbon samples were collected, and a wood-based activated carbon was selected as a comparison. The conventional adsorption performance indexes such as iodine value, methylene blue value, caramel decolorization rate and static adsorption capacity of tannic acid (TA) and humic acid (HA) were determined. Rapid Small-Scale Column Tests (RSSCT) was used to determine the breakthrough curves of activated carbon adsorption on water samples containing TA and HA to evaluate the dynamic adsorption performance of it. The pore structure and surface micro-topography of activated carbons were characterized by N₂ adsorption isotherms and scanning electron microscopy energy dispersive X ray analysis (SEM-EDS). Frenkel-Halsey-Hill model was used to calculate the fractal of activate carbons. The results show that the iodine value, methylene blue value, caramel decolorization rate, tannin acid isothermal adsorption capacity and humic acid isothermal adsorption capacity are obviously correlated with the pore development degree of activated carbon. The anthracite-based activated carbon had the best dynamic adsorption performance in the RSSCT, indicating that the dynamic adsorption performance of activated carbon was less correlated with the pore structure of activated carbon and more correlated with the surface roughness. Therefore, the activated carbon samples can be initially selected by the surface roughness. And then the RSSCT result of the HA is used to select an activated carbon with optimized adsorption capacity under the practical conditions of advanced drinking water treatment.

Research progress and prospect of energy security based on CiteSpace knowledge graph

Wang Wensheng, Zhang Jingjing

2021, 6(4): 497-508. doi: 10.19606/j.cnki.jmst.2021.04.015

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Abstract:
Using CNKI 2361 and WOS 5036 literatures as data sources, the knowledge map of "energy security" was constructed with the help of CiteSpace. The evolution, research hotspots and frontier trends of energy security research at home and abroad from 1992 to 2020 are compared and analyzed. The results show that energy security research has experienced three stages: initial germination, rapid development, coexistence of continuous development and volatility. There is no core group of authors at home and abroad, but obviously research teams have been formed. There is stable cooperation within the teams, but the cooperation between different teams needs to be strengthened. There are obvious differences in research content, research hotspots, and research frontiers between domestic and foreign research on energy security. Foreign research focuses on energy security issues in developed countries, the construction of energy security concepts and evaluation index systems, focusing on energy strategies, economic growth, energy reserves, and response to climate challenges and optimization adjustments, while domestic research focuses on China's status and role in the world structure, as well as climate change and other coping strategies, advocates global cooperation and common governance, and pays attention to the issues of "The Belt and Road, Global Energy Governance, and Energy Revolution".

2021 Vol. 6, No. 4