2024 Vol. 50, No. 7

Academic Column of Editorial Board Member
Research on a digital twin driven virtual debugging method for roadway automatic forming cutting
ZHANG Xuhui, LIU Yanhui, YANG Wenjuan, ZHANG Chao, DU Yuyang, YANG Junhao, YANG Wenyu
2024, 50(7): 1-11, 31. doi: 10.13272/j.issn.1671-251x.18186
<Abstract>(191) <HTML> (36) <PDF>(79)
Abstract:
In response to the problems of long debugging cycle, high debugging cost, high safety risk, and difficult quality evaluation in the current automatic forming and cutting control of roadways, a digital twin driven virtual debugging method for roadway automatic forming and cutting is proposed. Firstly, by using real-time appearance mapping (RTAP-MAP) technology to reconstruct the three-dimensional environment of the roadway, a control system model of the roadheader is constructed to form a virtual debugging environment. The virtual sensor technology is used to achieve precise mapping from physical space to virtual environment state. A performance evaluation method for roadway automatic forming cutting has been established to address the problem of difficulty in quantitatively evaluating the quality of section forming. Based on the recording of the section forming cutting control process in the data transmission center, the evaluation indicators of section forming precision, cutting efficiency and the number of oil cylinder switches, hard rock cutting adjustment, and over excavation and under excavation are mainly calculated. This provides precise feedback signals for the iterative optimization of deep learning algorithms. An automatic cutting control strategy that integrates reinforcement learning is proposed to improve the adaptability and precision of automated operations. To verify the effectiveness and accuracy of the virtual debugging method, an automatic control experimental platform for roadheader is built. The virtual debugging system is applied to the automatic control program for forming cutting of excavation roadway. The virtual simulation results show the following points. ① The maximum positioning errors of the X, Y, and Z axes of the debugged software at the control key points are 74.8, 72.93, 123.67 mm, respectively. It indicates that the positioning precision of the virtual debugging method meets the performance requirements. ② The trajectory of the virtual prototype is basically consistent with that of the physical prototype, indicating that this debugging method has achieved mapping to the physical space. The application result shows the following points. ① The reinforcement learning controller adapts to complex environments in virtual excavation testing, effectively converts virtual sensor inputs into precise control instructions, and verifies the feasibility of simulation reality transfer training. By processing real-time feedback on excavation precision and avoiding over excavation and under excavation, the controller learns and optimizes the strategy. ② The improved section forming cutting control performance has been improved. According to the control quantity timestamp records in the database, it takes 126 seconds, which is 8 seconds less than before the improvement. ③ After improvement, the maximum error in tracking the end trajectory of the cutting section is 6.0 mm, which is 0.3 mm lower than before. This avoids the under excavation caused by the shaking of the cutting trajectory and makes the trajectory and section smoother.
Research status and prospects of UWB radar life information recognition for mine rescue
ZHENG Xuezhao, MA Yang, HUANG Yuan, CAI Guobin, DING Wen
2024, 50(7): 12-20. doi: 10.13272/j.issn.1671-251x.2024060024
<Abstract>(183) <HTML> (67) <PDF>(52)
Abstract:
Ultra-wide band (UWB) radar can penetrate non-magnetic media such as coal and rock to detect life information of personnel after collapse. Due to the complex mining environment, UWB radar loaded with vital sign signals is prone to interference from environmental noise and clutter signals. It is difficult to recognize human subject information. This paper introduces the principle of UWB radar life detection system and its application in mine rescue. This paper summarizes the current research status of UWB radar life information recognition from three aspects: UWB radar life information extraction, dynamic and static human object recognition, and life quantification. This paper points out the current issues with the application of UWB radar life detection technology in the field of mine rescue. ① There is limited research on filtering methods for non-stationary signals and environmental noise in underground collapse environments. ② The extraction and representation methods for posture, behavior, life status, and other information of moving (or micro moving) objects need to be improved. The human life information recognition model is not yet perfect and the feature correlation between models is low. ③ There is a lack of solutions to the "overlapping" problem caused by multiple objects. This paper proposes the prospects for the research direction of UWB radar life information recognition for mine rescue. ① It is suggested to continuously optimize noise and clutter adaptive filtering methods for multiple types of mine disaster environments. ② It is suggested to construct a human life information recognition model suitable for the field of mine rescue. ③ It is suggested to further improve the quantification capability of multi-object after mine shelter. ④ It is suggested to conduct depth exploration of the method for determining the optimal detection frequency band for UWB radar.
Achievements of Scientific Research
Research on hydraulic control system for shield type temporary support robot driving under pressure
MA Hongwei, LI Lang, XUE Xusheng, WANG Chuanwei, WANG Saisai, ZHAO Yingjie, ZHOU Wenjian, ZHANG Heng
2024, 50(7): 21-31. doi: 10.13272/j.issn.1671-251x.2024030001
<Abstract>(172) <HTML> (58) <PDF>(49)
Abstract:
The shield type temporary support robot is an important component of the intelligent excavation robot system for large section roadways that adapts to the coexistence of dirt and debris. Its main function is to provide a safe and reliable workspace for achieving "parallel excavation and support" operations. In order to enhance the safe and stable support of the shield type temporary support robot for surrounding rock during its pushing and driving process, based on the structure, working environment, and operational requirements of the shield type temporary support robot, a mathematical model of its pushing amount and support force during pressurized driving, as well as a dynamic model of pressurized driving, are established. A hydraulic control system for the shield type temporary support robot driving under pressure is designed. The system mainly consists of a support hydraulic system and a driving hydraulic system. During static support, the support hydraulic system needs to constantly output a support force greater than the weight of the upper shield body itself, and the driving hydraulic system is in standby mode. When driving under pressure, the support hydraulic system and the driving hydraulic system work simultaneously, ensuring that the temporary support robot "reducing stress without leaving the roof" while steadily moving forward with the roof under pressure at all times. A precise control method for shield type temporary support robot driving under pressure based on fuzzy PID is proposed. The pressure and displacement signals of the temporary support robot are collected in real time by displacement sensors integrated on the displacement cylinder and pressure sensors in the hydraulic circuit. The signals are used to reflect the changes in support force and driving displacement during the temporary support robot's driving under pressure. Based on the error and error rate of the support force and displacement, the fuzzy PID algorithm is used to modify the control parameters of the support force and displacement, achieving reliable control of driving under pressure based on the fuzzy PID algorithm. Both simulation and experimental results show that the effect of fuzzy PID control is superior to traditional PID control. Under fuzzy PID control, the relative error of support force during the pushing and driving process of the shield type temporary support robot is less than 1%, and the driving displacement error is less than 2 mm. Moreover, the response speed of support force and pushing amount control is fast, ensuring the safe and stable support of the surrounding rock during the pushing and driving process.
Real time prediction technology for load bearing effect of hydraulic support after initial support based on data-driven approach
JIA Yifan, FU Xiang, WANG Ranfeng, ZHANG Zhixing, SUN Yan
2024, 50(7): 32-39. doi: 10.13272/j.issn.1671-251x.2024050061
<Abstract>(93) <HTML> (39) <PDF>(29)
Abstract:
In the actual production of coal working face, due to the roof conditions, mining influence, hydraulic support attitude and their mutual influence, the column pressure after the initial support of the hydraulic support may change, thus affecting the load bearing effect after the initial support of the support. The pressure failure of hydraulic supports after initial support may lead to problems such as coal wall lining, inter frame leakage, support leaning forward, and overturning. At present, most of the control strategies for the initial support force of hydraulic supports in intelligent mining working faces directly determine whether the column pressure reaches the rated initial support force when lifting the column. It lacks consideration for the load bearing effect caused by the change in column pressure after initial support. In order to solve the above problems, a real-time prediction method for the load bearing effect of hydraulic support after initial support based on column pressure data-driven approach is proposed. The method divides the historical data of column pressure within 3 minutes after initial support of hydraulic supports into 6 typical working conditions. The method classifies the 6 typical working conditions into effective load bearing or failure load bearing according to the different load bearing effects after initial support. Through correlation analysis, five feature factors affecting the load bearing effect of the support after initial support are identified. The method manually annotates the effective or failed load bearing samples of the column, and extracts features. The method inputs the feature values into four different algorithms: decision tree, random forest, support vector machine, and K-nearest neighbor (KNN) to establish classification models. After comparative analysis, the random forest model has the highest precision, reaching 95.60%, which basically meets the accuracy requirements of the model application. A real-time prediction model for the load bearing effect of hydraulic supports after initial support based on random forest is established. On this basis, a real-time prediction system for the load bearing effect of hydraulic supports after initial support is developed and deployed to coal mine sites. After continuous operation for 25 days, the system collects the column pressure within 3 minutes after the initial support of the hydraulic support and could output the load bearing effect of the hydraulic support within 5 seconds. The accuracy of the prediction results compared with the actual operation records is 82.48%, indicating that the system has high accuracy and stability in predicting the load bearing effect.
Research on the rapid construction platform of coal mine GIS one-map
HUANG Kun, JIANG Zhenpeng, YANG Xiaoyu, AN Ning
2024, 50(7): 40-46, 114. doi: 10.13272/j.issn.1671-251x.2024050055
<Abstract>(209) <HTML> (37) <PDF>(83)
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Currently, the engineering thematic maps used in coal mines are mostly CAD drawings. Extracting data efficiently from CAD drawings and quickly organizing them into geographic information system (GIS) services, thereby supporting the creation of mine spatial objects and business attribute expansion, integrating real-time safety production data are the key to building a coal mine GIS one-map. The implementation process of converting CAD drawings into GIS services based on the ArcGIS platform is cumbersome. The ArcGIS platform has high costs and cannot run well across platforms. In order to solve the above problems, a coal mine GIS one-map rapid construction platform has been designed. The platform includes three major functional modules: CAD drawing management, map service publishing, and thematic map management. The CAD drawing management module is used for basic information management and status tracking of drawings. The map service publishing module is used for map packaging and online preview. The thematic map management module is used for map service management, mine object creation, and attribute extension. Based on the open design alliance (ODA), the Teigha for Java SDK is used to achieve precise recognition and fast and accurate extraction of all elements in CAD drawings. By constructing a hierarchical description model for coal mine CAD drawing data based on GIS data features, rapid storage of all element data in CAD drawings has been achieved. Following the object-oriented design approach, a web-based coal mine CAD drawing dataset storage interface and thematic map service publishing platform are developed under the Spring Cloud framework, achieving rapid construction of coal mine GIS one-map. Taking the mining engineering plan of a certain coal mine as an example, traditional methods and fast construction platforms are used to construct coal mine GIS one-map. The comparison results show that the fast construction platform can significantly improve the efficiency of constructing coal mine GIS one-map, providing a spatiotemporal digital base for the intelligent construction of coal mines.
Impact hazard area classification based on multi factor coupled quantitative characterization model
JIA Haibin, LIU Aixin, ZHANG Bin, FU Xiangchao, CAI Wu
2024, 50(7): 47-54, 97. doi: 10.13272/j.issn.1671-251x.2024050015
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In response to the problem that existing impact hazard assessment methods cannot accurately reflect the features of stress concentration changes under the influence of impact hazard factors, an impact hazard area classification method base on multi factor coupled quantitative characterization model is proposed. Firstly, based on the geological conditions of the underground coal seam, the distribution of roadways, and the scope of mining, the main impact influencing factors are analyzed. Secondly, referring to the multi factor superposition method and stress analysis method respectively, the method determines the influence range and relative stress concentration coefficient of various impact influencing factors. Thirdly, based on the distribution function of micro element strength inside the coal rock mass, a multi factor coupled quantitative characterization model for impact hazard is constructed. Finally, the impact range and relative stress concentration coefficient of the impact influencing factors are input into the quantitative characterization model to obtain the stress distribution results of the coal seam. Based on the stress distribution results, the impact hazard level is classified, and the distribution of impact hazard areas is obtained. Taking the No.3 coal seam of Shandong Xinjulong Energy Co., Ltd. as an example, by analyzing the stress concentration caused by the main impact risk factors such as superimposed faults, large roadways, and goaf, a reasonable impact hazard level classification standard is formulated. The results of the impact hazard area classification of the No.3 coal seam are obtained and verified on site. According to the mining seismic events that occurred before and after the completion of the evaluation work, it can be seen that the impact source is mainly concentrated in the strong impact hazard area. It is consistent with the regional division results, thus verifying that this method can effectively quantitatively divide the coal seam impact hazard area.
Research on the features of impact damage in roadways in high stress fault structure areas
WANG Fei, LI Mingli, WU Yifan, CAI Dong
2024, 50(7): 55-63. doi: 10.13272/j.issn.1671-251x.2024050077
<Abstract>(117) <HTML> (40) <PDF>(27)
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The coupling effect of static and dynamic stress in fault structure areas exacerbates the risk of rock impact in underground fault areas. The stress distribution law and impact dynamic load response features of roadway surrounding rock in fault structure areas have significant peculiarities. At present, research on the impact of fault structures mainly focuses on the vicinity of the working face, but there is little research on the impact damage of roadways in fault structures. Taking the roadway in a deep buried high stress fault structure area of a mine in Shaanxi Province as the engineering background, the mechanical features of deformation and failure of the roadway surrounding rock in the fault structure area are analyzed. ① There is a significant stress barrier effect on the fault plane, and there are two special stress zones near the normal fault, namely the stress concentration zone in the hanging wall and the stress reduction zone in the lower wall. Due to the influence of the fault plane, the static load concentration stress of the roadway side shows an asymmetric distribution feature. The stress concentration on the side far from the fault plane is greater than that on the side near the fault plane, and the risk of impact damage to the surrounding rock of the roadway on this side increases. ② The fault plane has a significant barrier effect on the transmission of stress waves, and the dynamic load response of the hanging wall of the normal fault is greater than that of the lower wall. Due to the asymmetric distribution of stress on the two sides of the roadway, the dynamic load response of the right side is significantly greater than that of the left side. Based on the above features, a collaborative anti impact control technology of "unloading (large diameter drilling pressure relief) - support (stepped reinforcement into layered energy absorption and anti impact support)" is proposed for the surrounding rock of the fault structure area roadway. The engineering test results show the following points. ① After adopting the "unloading support" collaborative anti impact treatment measures for the roadway surrounding rock , the stress concentration areas of the two sides of the roadway are transferred to the deep part of the surrounding rock by 3-5 meters. The stress peak value is reduced by 18.5%-20.3%, and the stress concentration degree of the roadway surrounding rock is significantly reduced. ② Before the implementation of the "unloading support" collaborative anti impact treatment measures, the deformation of the roadway roof, floor, and two sides are 856, 334, 325, and 567 mm, respectively. The deformation and damage of the roadway surrounding rock are severe. After adopting the "unloading support" collaborative treatment measures, the deformation of the roadway surrounding rock decreases by 35.69%-62.03%, and the stability of the roadway surrounding rock is enhanced. ③ The coal powder content in the borehole is also significantly lower than the critical coal powder content, and the dynamic power of the roadway surrounding rock is reduced.
Overview
Current status and key technology prospects of shearer intelligent development
QIU Jinbo, LIU Cong, WU Haokun, ZHUANG Deyu, ZHU Shengqiang
2024, 50(7): 64-78. doi: 10.13272/j.issn.1671-251x.2024050039
<Abstract>(304) <HTML> (56) <PDF>(97)
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This paper introduces the current situation of intelligent development of shearer at home and abroad. The shearer is currently developing towards intelligent robotics and is in the primary stage of intelligence. This paper elaborates on the development process and trends of intelligent shearer. There are six scientific research projects that have played important roles in the intelligent development of shearer, including the UK remotely operated longwall face (ROLF) program, mine operating system (MINOS), NASA long wall automation cooperation project, Australian Australian coal industry’s research program (ACARP), Australian commonwealth scientific and industrial research organization (CSIRO) project, and EU new mechanisation and automation of longwall and drivage equipment (NEMAEQ). The development trend of shearer is to use continuously developing monitoring, sensing, and remote control technologies to replace manual intervention and operation, continuously improve the production efficiency and reliability of working face equipment, and develop towards informationization, integration, unmanned, and intelligent direction. This paper introduces the key technologies of intelligent perception, intelligent control, and intelligent communication of shearer. It points out that intelligent cutting technology based on coal rock recognition, intelligent drum speed regulation technology, precise positioning technology of shearer, and planning and mining technology based on three-dimensional geological models are key technologies that urgently need to be broken through. The human-machine relationship that cannot be ignored in the intelligent development process of shearer is discussed from two aspects: dust reduction and noise reduction.
Research status and development direction of 5G key technologies for coal mines
LI Chenxin
2024, 50(7): 79-88. doi: 10.13272/j.issn.1671-251x.2024040067
<Abstract>(551) <HTML> (25) <PDF>(107)
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Based on the current research results and practical experience of 5G in coal mines, this paper analyzes the research status and development direction of key technologies for 5G in coal mines from three aspects:5G private network architecture, coverage optimization, and intelligent application scenario construction. In terms of 5G private network networking for coal mines, two types of models, namely large-scale networking at the coal group level and independent private networks for mines, can meet the needs of 5G system construction and deployment for coal mines. In terms of enhancing 5G wireless coverage for coal mines: the wireless transmission performance of 5G for coal mines needs continuous research and improvement. At present, it is advisable to use low-frequency (below 1 GHz) multi carrier SUL (supplementary uplink) for optimizing the coverage of 5G for coal mines. To achieve breakthroughs and improvements in the explosion-proof safety power threshold of underground radio waves, it is necessary to synchronously increase the wireless transmission power on both sides of the 5G base station and terminal used in coal mines. It can optimize the overall coverage capability of the 5G system used in coal mines. Pre research on 5G coverage enhancement technology for coal mines based on 6G RIS (reconfigurable intelligent surface) is needed to provide further support for improving wireless coverage capabilities. In terms of building intelligent 5G application scenarios for coal mines, it is necessary to carry out joint technical research and development in the fields of mining equipment and mining communication. It is suggested to conduct research on the information physical mapping of equipment remote control based on 5G for coal mines and future autonomous group collaborative control of equipment. It is suggested to conduct research the expected functional safety mechanism of intelligent applications. It is suggested to develop 5G modules for coal mines that are small, lightweight, and fully compatible with industrial control protocols for on-site equipment.
Analysis and Research
YOLOv5s pruning method for edge computing of coal mine safety monitoring
CHEN Zhiwen, CHEN Ailiangfei, TANG Xiaodan, KE Haobin, JIANG Zhaohui, XIAO Fei
2024, 50(7): 89-97. doi: 10.13272/j.issn.1671-251x.2024010095
<Abstract>(109) <HTML> (43) <PDF>(37)
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At present, the combination of edge computing and machine vision has a good application prospect for coal mine safety monitoring. But the storage space and computing resources at the edge are limited, and high-precision complex visual models are difficult to deploy on it. In order to solve the above problems, a YOLOv5s pruning method based on indirect and direct evaluation space fusion (IDESF) is proposed for the edge end of coal mine safety monitoring, aiming to achieve lightweight YOLOv5s network. Firstly, a structural analysis is conducted on the convolutional layers of each module in the YOLOv5s network to determine the free pruning layer and conditional pruning layer. It lays the foundation for subsequent allocation of pruning rates and calculation of the number of pruning kernels. Secondly, the pruning rate is assigned to the prunable layers according to the convolutional kernel weight importance score based on the convolutional kernel weight magnitude and the relative computational complexity of the layers, which effectively reduces the computational complexity of the network after pruning. Thirdly, based on the direct importance evaluation criterion of convolutional kernels, the indirect output importance of convolutional layers is introduced into the direct importance space in the form of scaling factors. The position distribution of convolutional kernels is updated to construct a fused importance evaluation space that includes the output information and amplitude information of convolutional kernels. It thereby improves the comprehensiveness of convolutional kernel importance evaluation. Finally, drawing on the idea of topk voting, the process of median filtering for screening redundant convolution kernels is optimized. The method quantifies the degree of redundancy of a convolutional kernel in terms of the incidence of nodes in the adjacency matrix of a directed graph, which improves the interpretability and generality of the redundant convolutional kernel screening process. The experimental results show the following points. ① From the perspective of balancing model precision and lightweighting, YOLOV5s_IDESF with a pruning rate of 50% is the optimal lightweight YOLOv5s. On the VOC dataset, YOLOv5s_IDESF mAP@.5 and mAP@0.5 is the highest, reaching 0.72 and 0.44 respectively. The parameter count is reduced to a minimum of 2.65×106, the computational complexity is reduced to 1.16×109, and the overall complexity is also reduced to the lowest. The image processing frame rate reaches 31.15 frames per second. ② On the coal mine dataset, YOLOv5s_IDESF mAP@.5 and mAP@0.5∶0.95 achieve the highest values of 0.94 and 0.52, respectively. The parameter count is reduced to a minimum of 3.12×106, the computational complexity is reduced to 1.24×109, and the overall complexity is also minimized. The image processing frame rate reaches 31.55 frames per second.
Laser point cloud segmentation algorithm for hydraulic support based on neighborhood feature encoding and optimization
WANG Junfu, XUE Xiaojie, YANG Yi
2024, 50(7): 98-106, 178. doi: 10.13272/j.issn.1671-251x.2024040052
<Abstract>(80) <HTML> (30) <PDF>(15)
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Due to the influence of underground coal dust and easy obstruction, the laser point cloud data of hydraulic supports is prone to be incomplete. The existing point cloud segmentation algorithms are difficult to obtain fine-grained point cloud features, unable to obtain complete structural information of the point cloud. The algorithms are prone to introducing semantically dissimilar points in the neighborhood, resulting in low precision of laser point cloud segmentation for hydraulic supports. In order to solve the above problems, a laser point cloud segmentation algorithm for hydraulic supports based on neighborhood feature encoding and optimization is proposed. The method introduces a local neighborhood feature aggregation module consisting of neighborhood feature encoding module, neighborhood feature optimization module, and hybrid pooling module. The neighborhood feature encoding module adds polar coordinate encoding and centroid offset to represent the spatial structure of local point clouds on the basis of traditional 3D coordinate encoding, improving the feature extraction capability for incomplete point clouds. The neighborhood feature optimization module optimizes the feature expression in the neighborhood space by judging the feature distance and discarding redundant features, thereby more effectively learning the local fine-grained features of the point cloud and enhancing the local contextual information of the point cloud. The hybrid pooling module combines attention pooling and max pooling to obtain single point features with rich information by aggregating salient and important features within the neighborhood, reducing information loss. A neighborhood expansion module consisting of two sets of local neighborhood feature aggregation modules and residual connections is constructed to capture long-range dependencies between features, expand the local receptive field of individual points, and aggregate more effective features. The experimental results show that the algorithm has an mean intersection over union of 93.26% and an average accuracy of 96.42% on the laser point cloud segmentation dataset of hydraulic supports. It can effectively distinguish different geometric structures of hydraulic supports and achieve accurate segmentation of various components of hydraulic supports.
Path planning method for coal mine inspection robot
ZHU Hongbo, HUA Rong
2024, 50(7): 107-114. doi: 10.13272/j.issn.1671-251x.2024040033
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Path planning is a key technology for autonomous movement of inspection robot. The coal mine inspection robot has problems such as slow convergence speed and low search efficiency when planning paths using the rapidly-expanding random tree (RRT) algorithm. In order to solve the above problems, a combined force potential field guided RRT algorithm is proposed. The algorithm uses the repulsive force field in the combined force potential field to construct a dynamic step size. The coal mine inspection robot can adjust the step size near obstacles to improve the convergence speed of the algorithm. By utilizing the combined force field formed by the gravitational field in both the target node and random node directions, as well as the repulsive field generated by the nearest obstacle on the coal mine inspection robot, the generation direction of new nodes can be improved. It reduces the randomness of tree expansion and enhances the search efficiency of the algorithm. A pruning operation is performed on the paths planned based on the combined potential field guided RRT algorithm and smoothed using third-order Bessel curve. A simulation experiment is conducted in Matlab software on the path planning method of the coal mine inspection robot guided by the combined force potential field RRT algorithm. The results show that compared with the RRT algorithm and RRT* algorithm, the average path planning time of the combined potential field guided RRT algorithm in simple environments is reduced by 33.84% and 44.27%. The average path length is reduced by 15.29% and 4.42%, respectively. In complex environments, the average path planning time is reduced by 34.93% and 47.12%, and the average path length is reduced by 13.64% and 9.44%, respectively. In simulated coal mine environments, the average path planning time is reduced by 28.06% and 42.67%, and the average path length is reduced by 12.22% and 10.18%, respectively. After pruning and smoothing the path planned by the combined force potential field guided RRT algorithm, the number of turning points and angle changes in the path decrease, making the path smoother.
Recognition of violations in belt conveyor area based on multi-feature fusion for time-difference network
MA Tian, JIANG Mei, YANG Jiayi, ZHANG Jiehui, DING Xuhan
2024, 50(7): 115-122. doi: 10.13272/j.issn.1671-251x.2023080108
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The existing methods for recognizing violations in the underground belt conveyor area of coal mines suffer from insufficient feature extraction and difficulty in considering time differences in behavior. It results in low accuracy in recognizing violations (such as climbing, crossing, leaning, etc.) in the area. In order to solve the above problems, a belt conveyor area violation recognition method based on multi-feature fusion for time-difference network (MFFTDN) is proposed using the ResNet50 model. The method combines multi-feature fusion with time difference to perform multi-feature fusion on behaviors in different time periods. Firstly, the short-term multi-feature fusion (STMFF) module is introduced in the second and third stages of the original ResNet50 model, which concatenates the time and features from multiple consecutive frames together. Then the method performs time-difference calculation on the fused features, that is, the feature difference between adjacent frames, to capture local action changes in a short period of time. Secondly, in the fourth stage of the original ResNet50 model, a long- term multi-feature fusion (LTMFF) module is introduced to concatenate short-term multi-features from consecutive frames, and perform time-difference calculations on features from adjacent time points to obtain long-term multi- feature of behavior. Finally, the method classifies the fused features and outputs the recognition results. The experimental results show the following points. ① The average accuracy and precision of the MFFTDN based belt conveyor area violation recognition method have increased by 8.18% and 8.47% respectively compared to the original model ResNet50. It indicates that the simultaneous use of STMFF and LTMFF modules can effectively extract multi-feature information from different time periods. ② The accuracy of this recognition method on the self built dataset of violations in the underground belt conveyor area of coal mines is 89.62%, with an average precision of 89.3% and a model parameter size of 197.2×106. ③ The Grad CAM heatmap shows that this recognition method can more effectively focus on key areas of violations and more accurately capture violations in the underground belt area of the mine.
A method for updating sectional view automatically associated with mine 3D geological model
CHEN Yingxian, LI Jiaying, YANG Hongxia, YE Yongchao
2024, 50(7): 123-129, 164. doi: 10.13272/j.issn.1671-251x.2023120089
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During the process of open-pit coal mining, the 3D geological model of the mine is constantly changing. It is necessary to update the geological sectional view accordingly to truly reflect the current geological structure and stratigraphic properties of the mine. A method for updating sectional view automatically associated with mine 3D geological model is proposed to address the problem of inaccurate sectional view updates caused by poor interaction between internal graphic element attribute information and spatial information in current sectional view updating methods. By designing conceptual and logical models of the relationship between 3D geological models of mines and sectional view elements, the association between model elements and sectional view element object names can be achieved. By setting the positioning coordinates of horizontal and elevation positions on the sectional view, the objects obtained from the section are associated with the corresponding sectional view positions, achieving the association between the spatial position coordinates of the model elements and the sectional view elements. The purpose of associating the 3D geological model of the mine with the attribute information, spatial information, and other graphic data of the sectional view is achieved. The method determines the area that needs to be updated based on the changed graphic elements in the 3D geological model of the mine. The method extracts various section lines within the area, and obtain corresponding sectional views based on their correlation relationships. Further, by traversing and judging the status of the graphic element attribute update flag and geometric update flag, the method automatically updates the sectional view elements with changed attributes or geometric shapes in each sectional view. The application results show that this method achieves the correlation between sectional views and 3D geological models of mines, as well as automatic updating of sectional views. The accuracy of the sectional view update is verified by using this method to automatically update the positioning coordinate data in the sectional view, which is consistent with the pre update data.
A metadata standard construction method based on intelligent mine data classification and coding standards
WANG Ying, ZU Zishuai, WANG Zhenhua
2024, 50(7): 130-135, 146. doi: 10.13272/j.issn.1671-251x.2024020037
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Currently, the construction of intelligent mines is facing problems such as incomplete data standards, difficulty in integrating heterogeneous data from multiple sources, and the need to improve sharing mechanisms. Establishing a unified intelligent mine metadata standard is of great significance for forming a multi-source heterogeneous data fusion and sharing mechanism. Based on the intelligent mine data classification and coding standards, the construction method of intelligent mine metadata standards is studied. It is clarified that metadata standard construction is an extended research and value mining of data classification and coding. This paper defines the connotations of metadata entities and metadata attributes. This paper designs an intelligent mine metadata description framework that includes a basic description framework and an extended description framework. This paper provides basic metadata attribute description items that reflect the features of intelligent mine business scenarios, as well as extended metadata attribute description items for the four major thematic domain groups of basic, production, safety, and management in the intelligent mine data classification and coding standards, thus forming a metadata standard. Taking the inertial sensor of the shearer inertial navigation system in the production theme domain group as an example, the construction process of metadata standards is introduced. Building metadata standards based on intelligent mine data classification and coding standards can solve the problem of fusion and sharing of multi-source heterogeneous data, promote mine enterprises to manage, analyze, and apply data more efficiently, and improve the intelligence level of mine data governance.
Equivalent energy storage model coupled electromagnetic wave energy safety analysis of metal structures in underground coal mines
TIAN Zijian, HOU Mingshuo, SUN Jing, DU Xinxin, SHI Yangming
2024, 50(7): 136-146. doi: 10.13272/j.issn.1671-251x.2024050085
<Abstract>(105) <HTML> (44) <PDF>(22)
Abstract:
The electromagnetic wave energy emitted by wireless communication equipment in coal mines can be coupled and absorbed by surrounding metal structures, which poses a risk of igniting explosive gases in the mine. The existing research on the safety of underground metal structure coupled electromagnetic waves only focuses on the analysis of the energy of metal structure equivalent impedance model coupled electromagnetic waves. It lacks research on the energy storage process of metal structure coupled electromagnetic wave energy accumulated over time. In order to solve the above problems, an equivalent energy storage structure model suitable for studying the coupling-accumulation-release electromagnetic wave energy of metal structures is proposed, namely the metal structure equivalent capacitive energy storage model and the metal structure equivalent inductive energy storage model. Firstly, by using a low attenuation transmission line model, the relationship between the output power of the transmitting antenna, the distance between the transmitting antenna and the metal structure, and the induced voltage at the receiving end is derived. Secondly, an equivalent energy storage model of metal structure is established. The mathematical relationship between the receiving end parameters and the discharge spark energy is derived. The influence of the receiving end parameters on the discharge spark energy is analyzed. Finally, the mathematical relationship between the output power of the transmitting antenna, the distance between the transmitting antenna and the metal structure, and the discharge spark energy is derived by analyzing the relationship between the induced voltage at the receiving end and the effective value of the induced voltage. The influence of the output power of the transmitting antenna and the distance between the transmitting antenna and the metal structure on the discharge spark energy is analyzed. The theoretical reference safety points of the equivalent energy storage models of the two metal structures are given under the condition of other parameters being determined. The simulation results show the following points. ① For the equivalent capacitive energy storage model of metal structures, the discharge spark energy increases with the increase of the effective values of the equivalent energy storage capacitor and the induced voltage at the receiving end, and the safety point shifts to the left. The safety requirements for the effective values of the equivalent energy storage capacitor and the induced voltage at the receiving end become stricter. ② The energy of the discharge spark increases with the increase of the transmitting antenna power, and decreases with the increase of the distance between the transmitting antenna and the metal structure. The theoretical reference safety point of the equivalent capacitive energy storage model of the metal structure is obtained. ③ For the equivalent inductive energy storage model of metal structures, the discharge spark energy increases with the increase of the effective values of the equivalent energy storage inductance and the induced voltage at the receiving end, and the safety point shifts to the left. The safety requirements for the effective values of the equivalent energy storage inductance and the induced voltage at the receiving end become stricter. ④ The energy of the discharge spark increases with the increase of the transmitting antenna power, and decreases with the increase of the distance between the transmitting antenna and the metal structure. The theoretical reference safety point of the equivalent inductive energy storage model of the metal structure is obtained. ⑤ Comparing the theoretical reference safety points of two metal structure energy storage models, it is concluded that the danger of the metal structure equivalent capacitive energy storage model is much greater than that of the metal structure equivalent inductive energy storage model.
Features of adsorption pore structure in high-rank coal and its influence on methane adsorption capability
ZHANG Liming, LIN Jianyun, SI Leilei, ZHAO Qiongxiang, WANG Chen, WU Guopeng
2024, 50(7): 147-155. doi: 10.13272/j.issn.1671-251x.2024040083
<Abstract>(117) <HTML> (46) <PDF>(21)
Abstract:
The pore structure has a significant impact on the capability of coal seams to adsorb methane. But there is currently limited research on the features of adsorption pore structure in high-rank coal and its influence on methane adsorption capability. Taking the high-rank coal samples from Nuodong Coal Mine of Guizhou Xing'an Coal Industry Co., Ltd. as the research object, low-temperature N2 adsorption and low-temperature CO2 adsorption experiments are conducted. Combined with fractal theory, this paper studies the pore structure features of high-rank coal adsorption pores. Through high-pressure isothermal methane adsorption experiments, the influence of coal reservoir properties, pore structure features, and fractal dimension on methane adsorption capability is analyzed. The results show the following points. ① The pore morphology of high-rank coal reservoirs is relatively simple, mostly consisting of parallel plate pores and narrow slit pores with open ends. Micro pores dominate the pore structure of coal, with pore volume and pore specific surface area accounting for more than 98%, providing space for gas enrichment. ② The method calculates the comprehensive fractal dimension of high-rank coal pores based on the proportion of pore volume in different aperture segments, with micropore fractal dimension dominating the comprehensive fractal dimension. The pore structure of coal samples has obvious fractal features and strong heterogeneity of pores. ③ The Langmuir model can describe the adsorption behavior of high-rank coal. The physical properties, pore structure, and fractal dimension of coal reservoirs have a significant impact on methane adsorption capability. Langmuir volume is linearly positively correlated with maximum vitrinite reflectance, vitrinite content, ash content, and moisture content. It is linearly negatively correlated with inertinite content. The Langmuir volume is linearly positively correlated with the pore specific surface area and pore volume of the adsorption pores. The Langmuir volume is weakly linearly correlated with the fractal dimension. The research results can provide theoretical guidance for the exploration and development of high-rank coalbed methane and the prevention and control of coal mine methane disasters in southwestern Guizhou.
Experience Exchange
Structural planes recognition and occurrence statistics information collection method for high rock slopes
JIANG Shuihua, YU Qi, HUANG He, CHANG Zhilu, MENG Jingjing
2024, 50(7): 156-164. doi: 10.13272/j.issn.1671-251x.2024060021
<Abstract>(73) <HTML> (55) <PDF>(17)
Abstract:
Accurately recognizing the structural planes of high rock slopes and obtaining occurrence information are important prerequisites for conducting slope stability analysis. Unmanned aerial vehicle photogrammetry technology provides the possibility to solve the problem of accurate surveying of high slope structural planes. But it lacks efficient and accurate image post-processing methods. The existing research has not considered the uncertainty of structural plane occurrence information features, resulting in poor accuracy and efficiency in structural plane recognition. In order to solve the above problems, taking a high slope of an open-pit mine in Nanchang City, Jiangxi Province as the research background, an integrated method for recognizing structural planes and collecting occurrence information by integrating unmanned aerial vehicle photography, post-processing algorithms, and statistical analysis is proposed. Firstly, the method obtains surface images of the slope using the Phantom 4 Pro V2.0 unmanned aerial vehicle. Secondly, the method uses Context Capture software for processing, and the high-density 3D point cloud data is obtained. Secondly, the K-nearest neighbor (KNN) algorithm is used to determine the number of nearest neighbor points to construct a set of similar points. The density-based spatial clustering of applications with noise (DBSCAN) algorithm is used for clustering analysis to recognize slope structural planes, obtain structural plane occurrence information, and perform statistical feature analysis. Finally, comparative verification is conducted through on-site survey data. The results show that this method can quickly obtain complete high-density point cloud data, accurately and efficiently recognize most structural planes of high rock slopes. The recognition results are basically consistent with the actual situation of slope engineering sites. This method can obtain information on the number, occurrence, and statistical features of high slope structural planes. The probability distribution of most structural plane dip angles and inclinations fits well with the measured data, providing an important data source for the construction of high slope fracture network models and stability analysis.
Floor deformation control for roof cutting and pressure relief in gob-side entry retaining of deep buried mines
SUN Jingkang, TU Min, ZHAO Qingchong, DANG Jiaxin, ZHANG Xin, LI Yamian
2024, 50(7): 165-172. doi: 10.13272/j.issn.1671-251x.2024040096
<Abstract>(77) <HTML> (31) <PDF>(17)
Abstract:
Currently, research and practice on roadway floor heave mainly explore the deformation mechanism and control technology of roadway floor. The mechanical analysis of floor before and after roof cutting and pressure relief in gob-side entry retaining is not comprehensive. In order to solve the above problem, mechanical models of the surrounding rock and floor of the roadway before and after roof cutting are constructed based on the features of coal partition failure. The effects of solid coal, roadway support, and goaf on the floor are analyzed. The analytical solutions for the floor heave of the roadway before and after roof cutting are obtained. The conclusion is drawn that the elastic-plastic zone of the coal wall beside the roadway, the support structure of the roadway, and the load on the floor of the subsidence zone jointly affect the magnitude of the roadway floor heave. Numerical simulation is used to verify the features of rock mass failure, stress distribution, and changes in floor heave in gob-side entry retaining before and after roof cutting and pressure relief. The results show that roof cutting and pressure relief technology can effectively reduce the damage area on the solid coal side and top of the roadway, and maintain the stability of the roadway rock mass structure. The maximum stress of the roadway floor, the resistance of the roadway side support, and the amount of roadway floor heave all decrease, with an average decrease of 25.78%, 56.14%, and 54.07%, respectively. The on-site application results show that the amount of floor heave of thick hard top in gob-side entry retaining is reduced from 709.345 1 mm to 320.965 8 mm. The roof cutting and pressure relief technology can optimize the stress structure of the surrounding rock of the roadway, suppress the floor heave of the roadway, and effectively improve the floor damage.
Digital monitoring system for underground drilling in coal mines
ZHANG Youzhen, FAN Qiang, CHEN Long, CHEN Guo, SHUI Yang, LI Wangnian
2024, 50(7): 173-178. doi: 10.13272/j.issn.1671-251x.2023120075
<Abstract>(132) <HTML> (43) <PDF>(32)
Abstract:
A digital monitoring system for underground drilling in coal mines has been designed to address issues such as difficulty in measuring borehole bottom engineering parameters, insufficient accuracy and completeness of drilling data, and inadequate application of drilling data fusion. The system consists of a data source layer, a virtual model layer, a data processing layer, and a drilling service layer. The data source layer provides data support for the virtual model layer, which generates new data through simulation analysis and feeds it back to the data source layer. After receiving the data provided by the data source layer and the virtual model layer, the data processing layer performs data cleaning, transformation, and merging processes. The drilling service layer provides data display, query, analysis, alarm and other services to users at different levels through permission settings on the backend data management end. Drilling data is divided into pre drilling data (data obtained based on drilling design information and construction plans before drilling construction), real-time data (including parameters monitored by drilling process equipment and drilling site videos), and delayed data (parameters collected by drilling measurement devices at the bottom of the hole) according to temporal features. A data processing flow is designed for these three types of drilling data, and a system communication network architecture consisting of an access layer, a convergence layer, and a core layer is established. The engineering practice results show that the system has achieved the collection, transmission, display, and dynamic management of underground drilling construction data in coal mines. It meets the needs of monitoring and data management during the drilling construction process, and has good real-time and accuracy. This system provides technical support for intelligent construction and refined management of underground drilling in coal mines.