矿业科学学报

Risk identification, monitoring and early warning of typical coal mine dynamic disasters during the 13th Five-Year Plan period

Yuan Liang

2021, 6(1): 1-8. doi: 10.19606/j.cnki.jmst.2021.01.001

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Abstract:
Risk identification, monitoring and early warning of typical coal mine dynamic disasters such as rock burst, coal and gas outburst is the focus and difficulty of coal mine safety production. During the 13th Five-Year Plan period. In order to solve this problem, we carried out the research on the development of key technologies and equipment for risk identification, monitoring and early warning of typical power disasters in coal mines, a new theory of breeding and evolution mechanism and occurrence and development of coal mine dynamic disaster under the effect of mining disturbance and multi-field coupling superposition was established, the intelligent identification theory and early warning method of multi parameter precursory information of typical dynamic disasters in coal mines were put forward; the precursory information acquisition and sensing technology and equipment with fault self-diagnosis, high sensitivity and long calibration period were developed. Through the research of heterogeneous data fusion, ad hoc network, anti-interference and other technologies, the comprehensive collection of man-machine environment parameters and multi information in key areas of coal mines are proposed The new method of common network transmission provides technical support for the safe and trouble free operation of coal mine typical power disaster monitoring and early warning system. An automatic, informatized and intelligent early warning platform is constructed, which realizes the functions of fault self diagnosis, high sensitivity, short response time, long calibration period, anti-interference, etc., and the early warning accuracy is improved to more than 90 %. Through the organic integration of early warning basic research, key technology development and application demonstration has realized online monitoring, intelligent identification and real-time accurate early warning of hidden major disasters in coal mine have been realized.

Theoretical calculation model of time-space effect in subway station construction by PBA

Liu Bo, Fu Chunqing, Li Dongyang, Yang Hang

2021, 6(1): 9-20. doi: 10.19606/j.cnki.jmst.2021.01.002

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Abstract:
Aiming at the problems of structural dimension deviation, initial cracks and apparent defects in beam-column and other structures that occurred during the construction by Pile-Beam-Arch(PBA)approach, Based on the stochastic medium theory, a theoretical analysis model of the space-time effect of group tunnels excavation is established. The causes for the deviation of the building arches caused by the asymmetric construction are analyzed. Taking asymmetric excavation of 8 pilot tunnels in a typical PBA station as an example, the mechanism of uneven changes in stratum space caused by multi-step construction of pilot tunnels in large-span cross-section tunnels is researched. The essential cause of the deviation of the building arches is analyzed, and the deformation law of the surface settlement trough spatial shape swinging left and right with the excavation of the guide tunnel is reconstruced. According to the above research, it is pointed out that the arching being closed and looped, the rapid synchronization operation, the side hole divided into span building arches and construction optimization to achieve symmetric synchronization are the main countermeasures to eliminate or reduce the deviation of building arches.

Effect of arbuscular mycorrhiza and grass mulching on corn growth and soil water content in coal mining areas

Song Ziheng, Bi Yinli, Zhang Jian

2021, 6(1): 21-29. doi: 10.19606/j.cnki.jmst.2021.01.003

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Abstract:
Coal mining exacerbates drought stress and poor soil. How to improve the water use efficiency, promote plant growth and soil improvement has become the key to the field restoration. The soil type of the experimental area is aeolian sand soil, which is loose and has poor ability of water and fertilizer conservation. The experiment set up 4 treatments: control(CK), cover grass(F), inoculate arbuscular mycorrhizal fungi(M), cover grass combined with arbuscular mycorrhizal fungi(FM), with 3 repetitions for each treatment, thus there were 12 communities in total. The results showed that the biomass and yield of maize could be effectively increased by inoculation, and the yield of inoculated maize was 13 % higher than that of the control group. The yield of maize can be increased effectively by combining with the treatment of bacteria. After grass mulching in May, the soil water content in that month was 30 % higher than that of the treatment without grass mulching. In September, the precipitation was less, the evaporation increased, the evaporation of water was effectively reduced by grass mulching, and the water retention was 37.5 % higher than that of the treatment without grass mulching.

Study on the influence of above-crossing tunneling on the existing shield tunnels based on timoshenko beam

Wei Zheng, Jiang Yusheng

2021, 6(1): 30-41. doi: 10.19606/j.cnki.jmst.2021.01.004

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Abstract:
Based on the modified Loganathan theory, the longitudinal displacement of an existing tunnel caused by the ground loss in the process of shield crossing was studied. Timoshenko beam theory considering shear deformation was used to analyze the change of tunnel internal force and the amount of the dislocation between the adjacent rings. Based on the shear effect in elastic mechanics theory, the differential equation of tunnel longitudinal deformation was established and solved. After the bending deformation of Timoshenko beam, the difference between the beam cross-section of euler-Bernoulli beam which was not perpendicular to the neutral axis was analyzed. Furthermore, the variation of tunnel bending moment, shear force, and displacement between tunnel segments on tunnel shear stiffness and the ground loss ratio was studied. The results showed that the theoretical solution considering the shear deformation of the tunnel could predict the longitudinal deformation of the tunnel accurately. The proposed theory can correct the excessive internal forces such as bending moment and shear force without considering shear deformation and make up for the defect of unable to calculate the dislocation between the adjacent ring misalignment without considering shear deformation. The research results provide an effective method for predicting the influence of shield on existing tunnels.

Study on softening characteristics of mudstones in shallow buried strata in Xinjiang and countermeasures for tunnel support

Zhang Yong, Shi Fukun, Wang Junwei, Zhang Jiaxuan, Lu Hao, Sun Xiaoming

2021, 6(1): 42-50. doi: 10.19606/j.cnki.jmst.2021.01.005

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Abstract:
The Xinjiang water conveyance tunnel is a shallow buried mudstone stratum. After the water absorption, the strength of the surrounding rock softens and large deformation occurs. The support is difficult and the risk is high, which has a great impact on the progress of the project. In this paper, the mudstone of a water conveyance tunnel in Xinjiang is taken as the research object. Based on the XRD test analysis of the mudstone in the tunnel, the uniaxial compression and SEM analysis of the mudstone under different water content conditions are carried out, and the internal fissures of the rock sample are revealed. The variation of the pore structure clarifies the strength softening characteristics. The results show that the clay mineral content of the tunnel is as high as 50 %, and the proportion of montmorillonite is close to 90 %, which is easy to absorb water and soften. As the water content increases, the interior of the rock sample will undergo the process of micro-crack development, development and penetration, accompanied by the loss of pore water and internal minerals. By analyzing its saturated water absorption curve, the water absorption process is divided into three stages: rapid water absorption, decelerating water absorption and uniform water absorption stage. The Boltzmann prediction function is used to fit the rock sample strength variation curve after water absorption, and its strength can be changed. It is divided into three states: non-destructive strength, rapid softening and softening and rest state. The critical point for obtaining the softening of water absorption strength of this type of mudstone is 6 % water content; the comprehensive analysis shows that the water softening law is: the clay minerals in mudstone, mainly montmorillonite, have strong water absorption capacity. With the increase of water absorption, the free water content in the mudstone pores is significantly increased, the skeleton strength is gradually reduced, and an unstable state is formed, which is easily deformed and destroyed when subjected to external force. Based on this, the principles of stability control of such soft rock engineering are proposed, which is to determine the soft rock type and deformation mechanics mechanism, formulate targeted stability control strategies, and adopt the support of mechanical properties such as constant resistance, large deformation and high prestress material. The research results are of great significance for understanding the strength and softening characteristics of the mudstone in the water conveyance tunnel, the deformation and failure mechanism of the tunnel surrounding rock and the support design.

Experimental study on CO generation law of coal left in goaf in shallow-buried comprehensive and mechanized coal mining face

Yang Xiaobin, Nie Chaogang, Zhang Zipeng, Xiong Zichen, Pei Yanyu

2021, 6(1): 51-59. doi: 10.19606/j.cnki.jmst.2021.01.006

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Abstract:
In order to explore the law of CO generation in the oxidation process of coal leftover in shallow-buried comprehensive and mechanized mining areas, This article takes the shallow coal seam Gaojialiang Mine as the research object, and compares it with the deep coal seam Yangquan mine. Using the oil bath temperature-raising oxidation system, a temperature-increasing oxidation test was carried out on the coal samples of the fully mechanized coal mining face in different coal seams of Gaojialiang Mine and Yangquan Mine. Research shows: Each coal sample in the shallow-buried Gaojialiang Mine consumes O₂ at a low temperature of 40 ℃ to produce CO volume fraction of 1×10^-4; The oxygen consumption rate, CO production rate and heat release intensity of each coal sample during the oxidation and heating process gradually increase with the increase of temperature; The coal sample of the shallow-buried Gaojialiang Mine produced two critical temperatures of 40 ℃ and 130 ℃, corresponding to the starting point of accelerated oxidation reaction and the starting point of violent oxidation reaction, respectively. However, the Yangquan coal sample in the deep-buried coal seam has only one insignificant critical temperature, and relatively lagging behind, reaching 100 ℃~120 ℃. At the same coal temperature, the CO production and production rate of each coal seam in the shallow-buried Gaojialiang Mine, and the consumption and consumption rate of O₂ in each coal seam are significantly greater than those of the deep-buried coal seam in Yangquan Mine. The coal seams of the shallow-buried Gaojialiang Mine enter the accelerated oxidation stage earlier than Yangquan coal seams, and the required temperature is lower. The shallower the coal seam is buried, the faster the coal's oxygen consumption rate and CO production rate during heating oxidation., The increase in temperature promotes the oxidation exotherm of coal samples at shallow depths more strongly.

Study on the law of dynamic surface movement and prediction of mining under thick alluvium

Hou Defeng, Xu Shengjun, Qi Lingling

2021, 6(1): 60-70. doi: 10.19606/j.cnki.jmst.2021.01.007

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Abstract:
In order to study the dynamic subsidence law of ground under thick alluvium, based on the measured data, the evolution law of the surface dynamic movement parameters with the working face advancing was analyzed. The results show that the influence distance of the advance movement of surface, the maximum subsidence velocity of surface and its lag distance increase with the increase of mining distance of the working face. When the working face advances to about 350 m, the increase of the three parameter values decreases and finally stabilizes at 225 m, 34.5 mm/d and 124 m, respectively, thereafter, the curve of surface subsidence velocity moves forward with fixed shape and lag distance from the working face; based on multiple statistical analysis of mining cases in some domestic thick loose layer mining areas, the empirical relations between the maximum surface subsidence velocity and the tangent of its lag angle with geological mining parameters were constructed; finally, combined with the evolution law of the surface dynamic movement parameters, the prediction formula of the subsidence velocity of different points on the main cross section of the ground strike with the working face advancing to any time was constructed. The comparison with the measured value shows that the predicted accuracy can meet the needs of engineering practice.

Study on the law of influence by slurry viscosity on the fractured aquifer grouting and diffusion

Xu Yanchun, Zhang Ermeng, Zhao Lin, Shen Xingyu, Li Zhiyu

2021, 6(1): 71-81. doi: 10.19606/j.cnki.jmst.2021.01.008

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Abstract:
This study is to investigate the influence of slurry viscosity on the diffusion and filling of slurry during grouting reinforcement. Firstly, based on the newly developed test device, the diffusion process of three kinds of viscosity slurry in the aquifer of confined aquifer was simulated, and the law of slurry diffusion and filling was summarized. Fluent was adopted to simulate the grouting process. The stress distribution and variation law during the filling process of different viscosity slurries was obtained, the abnormal phenomena appearing in the physical test process was explained, and the elastic modulus of the rock mass after different viscosity slurry transformation by ultrasonic measurement was obtained. The results show that: In the process of high-viscosity slurrygouting, the formation of high-stressed cracks in the region is irregularly developed, and the slurry diffusion is deflected to the right; Under the same stress, the elastic modulus(λ)of the rock block is proportional to the viscosity of the slurry(μ_e), and the λ_max=108.07 % (μ_e=16.67)in the experiment; The medium viscosity slurry has a good transformation effect, and the area of the non-complete filling area is 23.35 %, and no abnormal phenomenon such as slurry accumulation occurs.

Experimental study on pumping pressure of pipeline transportation of hazardous waste

Guo Guangming, Zheng Xiaowen, Wu Miao

2021, 6(1): 82-90. doi: 10.19606/j.cnki.jmst.2021.01.009

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Abstract:
Mixing hazardous waste such as distilled residue and hazardous waste sludge which are piped to cement rotary kilns for incineration is the optimal method of co-processing of hazardous waste in China. Solid pump can be pumped over long distances is a difficult problem because the mixture is highly viscous and belongs to solid-liquid two-phase flow mixed with iron and wood. Firstly, the composition and mechanism of pipeline pressure is studied based on the principle of pulsating solid pump. Secondly, a mathematical model of pumping pressure suitable for engineering applications combined with the temperature difference coefficient, restart coefficient and yield stress coefficient was established. Thirdly, the pipeline pressure test platform was build. The results show that the pressure loss is 3.1 kPa at 35 % sludge mass fraction and the loss conversion coefficient of horizontal 1 m∶vertical 1 m∶horizontal 90°elbow∶vertical 90°elbow is 1∶3∶16∶18. Fourthly, the recommended sludge mass fraction is 35 % ~40 % by the slump test. Finally, the experiment showed that the pumping pressure increased exponentially with the increase of sludge mass fraction and was linear with flow velocity. The temperature difference coefficient is 1.5. The restart coefficient is 1.1 and the yield stress coefficient is 1.1.

Research on monitoring of moving ferromagnetic objects in open-pit mine crushing station based on low-frequency eddy current detection

Xu Jiangye, Zhao Sihai, Zhao Zexing, Liu Yuxiao, Sun Hailong

2021, 6(1): 91-99. doi: 10.19606/j.cnki.jmst.2021.01.010

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Abstract:
In the process of open-pit coal mine production, mining and transport loss of excavator accessories, iron and other large ferromagnetic objects with the coal into the crusher, will result in crusher jammed, broken tooth damage and even motor burn down and other serious production accidents, based on the principle of low frequency eddy current detection can effectively detect ferromagnetic objects, the characteristics of the ferromagnetic objects open-pit mine secondary crushing plant movement monitoring research. Taking SANDVIK's CR610/14—35 double-tooth roller sieve crusher as the experimental object, the mechanism of the detection system was analytically modeled according to the principle of electromagnetic mutual induction. The results of modeling and experiments show that the eddy current generated by ferromagnetic objects is weak due to the existence of strong background noise. The signal to noise ratio(SNR)can be improved by optimizing the parameters of the detector and planning the path of the detector. According to the characteristics of the experimental object, the maximum SNR was obtained when the ratio of the radius of the metal to the detection distance was 0.048, and the ratio of the coil radius to the detection distance was 0.044 5. In the 1~35 kHz segment, the SNR is higher in the low frequency band than the high frequency band. The initial value and response time of the path entering the detection area perpendicular to the detection axis have obvious advantages over the path entering the detection area parallel to the axis.

SSD-LeNet based method of mine moving target detection and recognition

Zhang Fan, Luan Jiaxing, Cui Donglin, Xu Zhichao

2021, 6(1): 100-108. doi: 10.19606/j.cnki.jmst.2021.01.011

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Abstract:
Aiming at the problems of low detection accuracy and low real-time performance in the detection and recognition of mine moving targets in foggy and low-illumination environment, a method based on deep convolutional neural network for intelligent detection and recognition of mine moving targets is proposed. The visual sensor is used to capture a frame of the underground mine scene to construct the environment model. The original image of the moving target is used as the model input, and the digital identifier is embedded in the specific position of the moving target image, which creates a data set containing the digital sequence position information. A novel off-line training model named single shot multibox detector(SSD)is presented, which can output target feature categories corresponding to its position. Then, the trained SSD learning model is used to detect the position of the digital sequence on the moving target image in the test set, and characters are split according to the rectangular region corresponding to the position of the digital sequence. Furthermore, the segmented single characters are put into the LeNet-5 network for sequential recognition The recognized single characters are sequentially combined into a digital sequence, thereby quickly retrieving the identity information of the mobile target. The research shows that compared with other target detection and recognition methods, the proposed method has higher accuracy and robustness for target detection and recognition under low-illumination and noisy environment, and can meet real-time requirements.

Study on the removal of benzenes pollutants from coal chemical wastewater based on ozonation technology

Peng Siwei, He Xuwen, Liu Haiyang, Bai Yuyong, Gu Xiaobing, Li Yehong

2021, 6(1): 109-114. doi: 10.19606/j.cnki.jmst.2021.01.012

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Abstract:
Benzene, toluene, ethylbenzene and xylene(BTEX)are typical organic pollutants in coal chemical wastewater, which were difficult to be biodegraded under normal conditions, and were often removed by chemical means in the actual production process. This study based on the strong oxidizing free radicals generated in the process of ozone oxidation, used ozone oxidation technology to remove BTEX in simulated wastewater. The effects of pH value, temperature, ozone dosage and ozone dosing mode on the degradation of BTEX were investigated. The reaction mechanism of degradation by ozone was explored by using tertiary butanol as hydroxyl radical inhibitor and free radical dismutase as superoxide radical inhibitor. The results showed that the degradation effect of BTEX was the best when pH was 8, reaction temperature was 30 ℃, ozone dosage was 3.5 g/L and ozone dosage mode was countercurrent. The existence of superoxide radicals and hydroxyl radicals were the fundamental reason for the effective removal of BTEX from water by ozonization.

Machine vision detection of foreign objects in coal using deep learning

Wang Weidong, Zhang Kanghui, Lü Ziqi, Gu Zhaochuang, Qian Hanwen, Zhang Qingyi

2021, 6(1): 115-123. doi: 10.19606/j.cnki.jmst.2021.01.013

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Abstract:
In the process of coal processing, due to the limitation of mining conditions, a large number of foreign objects are mixed into raw coal, which leads to clogging of heavy medium system pipelines, seriously affecting the production efficiency and restricting the improvement of coal quality. In order to effectively solve the impact of foreign objects in coal, machine vision technology is used to complete the detection and removal of foreign objects. Owing to irregular shapes and complex features for foreign objects in coal, a multi-scale feature fusion semantic segmentation network structure is proposed for end-to-end detection of images of foreign objects collected at the actual production site. In the network, the encoder uses residual convolutional blocks to extract features and captures context information, and the multi-scale feature map obtained by the pooling operation is fused at the decoder. The encoder and decoder are connected by layer jump to better combine the background semantic information of images for end-to-end training. The cause of model misdetection was analyzed through the visualization method of class activation map, a loss function was proposed to alleviate the model misdetection caused by the surface and background interference of coal and gangue, and the results were refined using conditional random fields to get a binary image. The experimental results show that the model can effectively segment the foreign bodies in the coal gangue system, and the mean intersection over union of the model on the test set is 77.83 %.

A survey of digital mine and mine safety management based on Citespace

Yang Yang, Zhang Wenbo, Zhang Jianmin, Zuo Chenxi

2021, 6(1): 124-138. doi: 10.19606/j.cnki.jmst.2021.01.014

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This paper, taking the Chinese and English literature of mine safety and digital mine safety management from 1999 to 2019 as the research object, using Citespace visualization software as the research tool, systematically sorted out and analyzed the highly cited literature from the number of documents, research topics, major scholars and research institutions, keywords and keyword centrality. The results show that: papers on mine safety from the perspective of digital mines account for about 20 % of the research papers in the field of mine safety, and show an upward trend year by year, indicating that the related research of digital mines in the field of safety management has always been a hot spot in this field; Most cited Chinese documents are theoretical methods or management studies, while highly cited foreign documents are mostly engineering and technical studies, indicating that there are certain differences between Chinese and foreign academic journals. 61.9 % of the authors of foreign literature are from China, which shows that Chinese scholars have made a great contribution to the research in this field. It also shows that Chinese scholars have taken theoretical method research, management research, and engineering technology research into account at the same time. Current research at home and abroad has a high degree of concentration, strong research intensity, and strong forward-looking nature. It has basically realized the combination of emerging technologies and the safety management of digital mines, which provides the necessary theoretical support for the application and development of digital mines in mine safety management.

2021 Vol. 6, No. 1