Coal Mine Disaster Research Articles

Prediction of dilatancy of tunnel surrounding rock in coal measure strata: A case study of Huainan mining area

In this study, the dilatancy of tunnel surrounding rock in coal measure strata was comprehensively investigated by means of field monitoring, theory analysis and algorithm analysis. The study reveals that dilatancy is related to many phenomena of coal mine disasters such as gas outburst, rib spalling and rock burst. Accordingly, the method of predicting these phenomena through dilatancy monitoring was proposed. Furthermore, a method based on support vector machine was proposed to predict the dilatancy of coal seams, and the dilatancy limit of coal and rock mass was defined as the criterion for judging whether a working face was to undergo dynamic disasters. A working face will undergo disasters when its dilatancy exceeds the dilatancy limit, in which case the support of working face should be strengthened. The criterion was then verified in the stope. The research results have important guiding significance for prediction and prevention of coal seam disasters.

탄광사고를 통해 살펴본 사북사건의 배경

탄광사고를 통해 살펴본 사북사건의 배경

A Study on Transient Electromagnetic Interpretation Method Based on the Seismic Wave Impedance Inversion Model

Abstract A comprehensive transient electromagnetic interpretation method based on seismic wave impedance inversion has been proposed according to the advantages of seismic and transient electromagnetic exploration methods to mitigate of hidden water inrush disasters in coalmines. Combined seismic wave impedance inversion results and resistivity logging data, the method was used to establish a geo-electric model. The stratigraphic horizon and the stratigraphic electrical characteristics were determined by the wave impedance inversion data and the resistivity logging data respectively. Furthermore, the structure and water-bearing property in the stratum were estimated by the analysis of the difference between the measured transient electromagnetic data and the calculated data from the forward model. The numerical calculation of the fault-containing model shows that the comprehensive interpretation method could determine the water-bearing capability of the fault as well as it tendency. An advantage of this new method is the effective avoidance of the influence of low-impedance overburden on the data interpretation. The practical application can accurately explain the location and the water-bearing property of the disaster-causing factors of the hidden water inrush in the coalmines.

An improved rotated staggered grid finite difference scheme in coal seam

Coal seam is thin compared to the wavelength of seismic wave and usually shows strong anisotropy. It may form special geological bodies such as goaf and collapse in coal mining. The existence of these phenomena may lead to instability in numerical simulation of goaf area in coal seam. And the calculation speed of simulation is always a factor that restricting the development of simulation technique. To improve the accuracy and efficiency of seismic numerical simulation of goaf area, an improved vacuum method has been imported in a rotated staggered grid scheme and the calculation is implemented by combining parallel computing and task parallelism. It makes sure that the numerical simulation method can be utilized in a geological model with large differences in elastic parameters among layers and improve the performance of a parallel application by enabling full use of processor resources to expedite calculation speed. We set up anisotropic coal seam models, and then analyze the characteristics of synthetic seismograms and snapshots of different goaf areas with or without collapse by modeling. Results show that the proposed method can accurately simulate the goaf area and the calculation method can run with high speedup ration and parallel efficiency. The research will further advance the technology of anisotropic seismic exploration in coal fields, provide data for seismic inversion and give a theoretical support for coal mine disaster prediction.

Research on Ground of Penetrating Radar in the Coal Mine Detecting: A Case Study of Application in Huaibei Coal Mine

Although many geophysical techniques have been used to detect the disaster geological anomalous body in the Huaibei coal mine company, there are still many mining disasters happening. The main reason is that the coal seam is rich of water in Huaibei coal areas. If the ground water connects with tunnels, it will cause the flood to collapse the coal seam. However, these dangerous geological bodies usually are very hided from the viewpoint of traditional electromagnetic and seismic methods. Due to the great difference of permittivity between the water-bearing rock and the surrounding rock, the high frequency electromagnetic wave can be received by a Ground Penetrating Radar (GPR) to detect the water-bearing rocks. Hence, we try to employ the high frequency electromagnetic wave to detect the water-bearing rock, which frequently results in a coal mining disaster. Firstly, the numerical simulations based on the theory research and its` effectivity analysis are done. Then, the method is used for the coal mine of Huaibei Company. Finally, the comparison between the detected results and the geological drilling information indicates the detection effectiveness of the GPR (Ground Penetrating Radar) in the coal mine tunnel.

Real-time measuring and warning of surrounding rock dynamic deformation and failure in deep roadway based on machine vision method

Surrounding rock deformation measuring, which reveals the temporal and spatial evolution rules in deep roadway, is an effective method of preventing dynamic disasters in deep underground coal mines. The current roadway deformation measuring methods have deficiencies of long measurement interval, poor continuity and low-level automation. Therefore, in this paper, a real-time monitoring method and system of roadway deformation based on machine vision were established, and the multi-index early warning criterion of roadway deformation and failure was built. The real-time monitoring on the dynamic deformation of roadway was carried out using the deformation amount, speed and acceleration of surrounding rock as dynamic early warning indexes. The rock real-time image was automatically collected by the machine, processed to restore the current state of surrounding rock. According to the study of two cases in underground coal mines, the real-time monitoring method of roadway deformation system was applied and validated in Chang Gou Yu (CGY) and Zhang Shuang Lou (ZSL) Coal Mines for monitoring the surrounding rock dynamic deformation process. The multi-index early warning criterion of roadway deformation and failure was applied to evaluating the state of the surrounding rock and warning the instability of it. The results show that the indexes could reflect the state and development trend of surrounding rock deformation and failure. The dynamic characteristic, which was consistent with the stress concentration, could be used as the precursory information of surrounding rock instability. The machine vision roadway deformation real-time monitoring system could realize regional, continuous and real-time monitoring and early warning of underground roadway deformation.

Experimental Analysis of the Dynamic Effects of Coal–Gas Outburst and a Protean Contraction and Expansion Flow Model

As one of the most serious dynamic disasters in underground coal mining, coal–gas outburst (CGO) leads to very high casualties and economic losses. To research the dynamic effects of disasters and further understand the mechanism of CGO, a large-scale physical simulation test system for coal mine dynamic disasters was used to conduct experiments. The results of this research indicate that there is an obvious choking phenomenon when the pressure drops in coal seams; the direction in which the pressure drop zone extends is consistent with the CGO cavern under the action of the geo-stress. The patterns of the two-phase flow of a CGO can be classified into three types: spurting flow, sparse flow and dense flow. There is a significant secondary acceleration process during the motion of pulverized coal in the roadway. The deposition characteristics of CGO coal exhibit a normal distribution in the roadway. In addition, the sedimentation of CGO coal has a good correlation with its particle size. In the initial stage of the CGO, the flow pattern in the roadway is dominated by weak disturbances, which are then superimposed as strong shock waves in the middle of the roadway. Based on the experimental results, a protean contraction and expansion flow model that contains a key structure for outbursts is proposed, and this model can properly describe the dynamic effects of the CGO based on fluid flow patterns.

Escape route optimization by cellular automata based on the multiple factors during the coal mine disasters

When disaster occurs in coal mines, the complex network structure of roadways and the disaster evolution process usually cause serious casualties. An efficient escape plan becomes an important method to guarantee survivors. The factors affecting the miners’ escape during the disaster were analyzed. An experimental model was established based on the key factors such as the slope, the convex–concave degree, and the speed of the airflow. The equations between the key factors and the escape speed were fitted by a large number of experimental values. A quantitative model of high temperature, CO, CO2, and O2 concentrations, visibility, and other environmental factors related to the dynamic health of the miners was set up. A cellular automata model for the shortest route selection in the complex ventilation network was established. In order to solve this problem, we established a physical model of the ventilation system in the Tang Shan-gou coal mine. The static difficulty degree of the roadways in the complex network was calculated by classification and segmentation. The parameters such as temperature and the components of the fire smoke in the roadways were simulated by the fire dynamics simulator. The cellular automata model was improved, the static difficulty was set as the primary selection factor, and the dynamic healthy degree was set as the secondary factor. From the simulated disaster drills carried out by the miners and the numerical simulation results, we proved that it is reasonable and feasible to use the improved cellular automata model for the personnel escape route optimization.

The mechanical effect of typical dynamic disaster evolution and occurrence in coal mines

ABSTRACTCoal and gas outburst and rock burst disasters have obvious dynamic effects in the process of development and occurrence. It is considered as two typical dynamic disasters. In order to study the mechanical effect and characteristics of typical dynamic disasters in underground coal mines, this work analyzed the stress source on coal and surrounding rock, the mechanism of typical dynamic disasters, and the mechanical appearance of dynamic disaster evolvement and occurrence. The results show that there is a significant mechanical effect in typical dynamic disaster evolution and occurrence. The stresses that cause typical dynamic disasters mainly include tectonic stress, the original stress of the coal and rock, and mining-induced stress. Stress is the necessary condition for the occurrence of typical dynamic disasters and plays a leading role in the gestation process of typical dynamic disasters. The stress effect is slow but persistent in a typical dynamic disaster evolution process, and the stress effect is rapid and dramatic in the process of dynamic disaster occurrence. This work puts forward Technical measures to reduce the hazards of typical dynamic disasters combining the stress effects in a typical dynamic disaster evolution process, and the effectiveness of the measures is verified in engineering practice.

Effects of pore structure and methane adsorption in coal with alkaline treatment

Coal bed methane (CBM) is an important type of clean energy, but it can also result in coal mining disasters. Increasingly more technologies have been applied to improve the effectiveness of gas extraction. Coal contains a large number of organic minerals and inorganic minerals, and some inorganic minerals fill in pores and block the gas seepage. To improve the connectivity of coal pores, chemical methods can be used to change the distribution of the minerals in coal. In this paper, representative bituminous (TY) and anthracite (QC) are used, and an alkaline solution is also used to treat the coal samples. The SEM results show that some minerals in coal can be dissolved in alkaline solution and removed from the pores, thereby changing the distribution of the minerals. According to the LTNA test, the micropore content of coal is changed, especially in the pore size range of 2–5 nm. With the alkaline treatment, the average aperture decreases and the specific surface area increases. Fractal theory was used to analyze the data with relative pressure (P/P0) less than 0.5. The results showed that the fractal dimension of the coal sample increased after the alkaline treatment, which indicated that the micropore content of the coal sample increased due to alkaline erosion. To verify the pores changes, adsorption experiments were carried out to analyse the adsorption capacity of the coal samples. After the alkaline treatment, the maximum sorption capacity and Langmuir-like pressure both increased. CO2 injection is an effective technology to displace CBM, but it easy to leave a great deal of CO2 in coal. The residual CO2 could be reduced by injecting an alkaline solution, and the coal would also be eroded. Based on the results, a new method combining CO2 injection and an alkaline treatment was proposed to improve the effectiveness of the gas control.

A Tightly Coupled GIS and Spatiotemporal Modeling for Methane Emission Simulation in the Underground Coal Mine System

Mine safety is of primary concern in the underground coal mining system. At present, there is a lack of an efficient platform to manage the numerical simulation procedure and inherent spatiotemporal data for coal mine disasters. This necessitates the coupling of spatiotemporal model with geographic information system (GIS) in practical application. Here, a novel spatiotemporal model tightly coupled with GIS is presented to improve the model-data integration. Such tight coupling is achieved by developing a lattice Boltzmann method (LBM) based turbulent model with an underlying shared FluentEntity model within the LongRuanGIS platform. The case study and comparison with the traditional computational fluid dynamics (CFD) method demonstrated that the platform is capable and effective in providing functionalities for lattice domain decomposition, simulation, visualization and analyses, as well as improving the computational efficiency. The proposed approach and platform, promising for the disaster prevention, offer a template for future GIS-Model integration and also applicable for other underground coal mine disasters.

Flow field evolution during gas depletion considering creep deformation

Unsteady creep of coal seams and the resultant abnormal flow of coal seam gas are the main reasons for dynamic disasters in deep mines. In this study, for investigating the evolution of gas depletion in deep mines, the flow field evolutions during gas adsorption and desorption were simulated first based a multi-field (coal deformation field, diffusion field and seepage field) coupling model considering the creep deformation. Firstly, a laboratory experiment was performed to validate the mathematical model. Then, spatial and temporal evolutions of matrix and fracture gas pressures, coal permeability and equivalent stress during gas adsorption and desorption were analyzed. The results show that in the initial stage of adsorption, gas pressure in fractures increases rapidly under the action of pressure gradient. As the gas gradually diffuses into matrix pores, gas pressure in the matrix goes up, which results in swelling deformation of coal matrix and alters the fracture aperture. Accordingly, coal permeability and equivalent stress were affected. During the desorption process, gas pressure in fractures drops rapidly at first, and then it falls at a lower rate. The diffusion of gas into fractures gradually leads to matrix shrinkage and enhances coal permeability. With a decrease in fracture gas pressure, the equivalent stress of coal declines rapidly first, followed by a slow rise induced by the diffusion of gas in the matrix. Furthermore, changes in the amount of gas desorption was analyzed by fitting the experimental test data in a specific time, which verified rationality of the mathematical model. The study can provide theoretical guidance for prevention and control of dynamic disasters in coalmines and the gas pre-drainage through borehole in deep mines.

Coal Mine Flood Risk Analysis based on Fuzzy Evaluation Method

Coal mine flood accident is one of the five major disasters in coal mine. It often causes catastrophic damage with high number of human injuries and deaths. The prevention and control of coal mine water hazards is an important task of coal mine safety management. This paper discusses the use of fuzzy evaluation method to identify the sources of danger of the flood accidents, and analyzes the flood accident risks according to the actual coal mine situations. The author hopes that this paper can play a guiding role in the prevention and control of the coal mine flood accidents.

Characteristics of microseismic waveforms induced by hydraulic fracturing in coal seam for coal rock dynamic disasters prevention

Coal rock dynamic disasters have been a persistent threat to mine safety. Hydraulic fracturing(HF) technique has been proved to be an effective method for preventing coal rock dynamic disasters in underground coal mines. In order to monitor the crack extent of HF in coal seam, highly precision microseismic(MS) data acquisition apparatus and sensitive sensors are employed to monitor the cracks induced by coal seam HF in Xieqiao Coal Mine. Lots of effective and weak MS waveforms induced by HF are successfully recorded. Some useful methods such as wavelet transformation, Hilbert-Huang transformation, envelope analysis and curve fitting method help to make comprehensive insights into the amplitude-frequency, time-frequency, duration and peak following attenuation characteristics of these HF induced MS waveforms. The frequency, duration time and peak following attenuation characteristics of MS waveforms induced by mining, blast and coal seam HF are statistically studied. The results show that these characteristic parameters, peak frequency, duration time and peak following attenuation, are very sensitive to distinguish these three typical kinds of induced MS waveforms. Further study shows that the principles of fractures’ propagation influenced by the pressurized water and the backfill effect of pores by large volume of pressurized water injection and the pressurized water itself are the key factors influencing the characteristics of MS waveforms. The conclusions are the theoretical basis of locating the cracks and monitoring the effect of HF in coal seams by using MS technique, which can provide the basis reference for designing optimized, safe and effective HF program to prevent the coal rock dynamic disasters, and will be of great significance to coal mine safety.

Everyday practices of memory: Authenticity, value and the gift

This article develops theories of collective memory by attending to the everyday practices and meaning-making involved in creating and sustaining sites of heritage. While research across disciplines linked to memory studies has increased in recent years, with a notable sociological contribution, as yet ethnographic understandings of how collective memory is produced and maintained through locally situated and embedded practices are not fully realized. Our research took place in the village of Six Bells in the South Wales Valleys, where living memory of a coal mining disaster in 1960 and coal mining itself are slowly disappearing. One of ways in which the people of Six Bells are remembering and commemorating this past is by giving their narratives and artefacts to the community’s ‘heritage room’ as gifts. This form of remembering, prompted by an extraordinary event and the rapid social change associated with deindustrialization, produces and sustains legitimate representations and imaginaries of the past. By developing anthropological understandings of gift exchange, we propose that these practices are one visible component of the claims to authenticity and the bestowal of value active in the memory work of everyday life. We attend to three interrelated characteristics of gift exchange to develop our argument; the importance of the personal in producing authenticity through the gift relation; the provenance and social impetus of the act of giving; and the systems of reciprocity generated across and between generations, which work to assign value to the gift itself.

Multifractal characteristics of gas disaster accident in coal mine

In order to explore the law of development and the characteristics of evolution of death toll caused by gas disasters in coal mine, with the multifractal detrended fluctuation analysis (MF-DFA) method, we analyzed the three time series of death toll caused by gas disaster, coal and gas outburst, and gas explosions in coal mine from 2006-2015 in China. It concluded that all of three time series have multifractal characteristics, the multifractal spectrum width Δαtc > Δαbz > Δαws, and the largest fluctuation and multifractal intensity of death toll time series of coal and gas outburst. The multifractal spectrum function f(α) is right hook-shape, and the Δf <0, it forecast that three kinds of time series are likely to rise in the future, which coincided with the upward trend of the number of coal mine gas accidents and deaths toll in 2016. The results shows that MF-DFA theory reflect the complex nonlinear dynamic mechanism of gas disaster system in coal mines, and provides a theoretical basis for the prediction of gas accidents in coal mines. The multifractal theory of detrended fluctuation reflects the complex nonlinear dynamic mechanism of gas disaster system, and provides a theoretical basis for the prediction of gas accidents in coal mines.

RETRACTED ARTICLE: Mine accident prediction and analysis based on multimedia big data

Coal mine disaster early warning based on multimedia big data is an effective measure to avoid accidents such as gas, water, fire and rock burst, and to reduce casualties and property losses. Through the analysis of various data of coal mine, the analysis model is established and the correlation analysis is carried out, so as to better carry out risk early warning and prediction analysis, provide early warning and prediction information for supervision and law enforcement, and improve the scientific nature of supervision and law enforcement and the ability of early warning and prediction for accident risk. Aiming at the analysis and prediction of large mine accident data, the modeling and Simulation of large mine accident data analysis and prediction based on decision tree-BP neural network are carried out. The report of coal mine gas accident is analyzed by using the method of multimedia large data mining, and the key factors of coal mine gas accident are identified. Therefore, we can focus on strengthening the monitoring of accident factors, reduce the risk of accidents from the source, and improve the safety management level of coal mines.

Design and optimisation on rapid rescue well-drilling technology with large-diameter pneumatic hammers

ABSTRACTRescue drilling with large-diameter escape shafts is the most efficient methods to get through the trapped miners. In order to improve the penetration rate of rescue drilling technology during underground coal mine disasters, the large-diameter RC pneumatic hammer has been designed and numerically optimised. Meanwhile, the suction capacity of the RC pneumatic hammer has been investigated, including relevant field tests. Field test results have shown that the maximum penetration rate of the RC pneumatic hammer is 4.55 m/h while drilling in sandstone and limestone formations. The designed large-diameter pneumatic hammer dramatically reduces the drilling time in the rescue operation of mine accidents.

Research on Gas Drainage Pump Design and Prevention Measures in Gas-rich Mine

In gas-rich mines, gas problems exist in the process of mining, which not only increases the difficulty of mining coal resources, but also reduces the production of coal mines safety. Typically, gas explosion was one of the most serious disasters in coal mines, which caused large numbers of casualties and destruction of facilities. In order to prevent the gas accident during the mining process in the coal seam of Tashan Mine (which located in Datong, Shanxi Province, China), the No.3~5 coal seam were taken as an example, the gas drainage pumps and the pipe laying methods were designed, basing on its hydrogeological conditions, development methods and coal mining methods. The gas drainage pump with a flow rate of 309.95 m3/min was designed, which helps to make better use of existing mine gas resources better and more efficiently. In addition, integrated control technologies such as gas drainage, gas concentration monitoring, effective ventilation and control of fire sources were used to reduce the probability of gas explosion in the No.3~5 coal seam of Tashan Mine. Strengthen the prevention and control of gas disasters, so as to ensure the smooth progress of coal mine safety production. The gas drainage system has built with this design, which runs for several months, and achieved a good performance. Therefore, the design approach can be referred to other similar mines.

The Turkish Soma Coal Mining Disaster

On May 13, 2014, a fire due to the combustion of accumulated methane gas in the Soma Eynez Mine in Turkey killed 301 miners. This case chronicles the events on the day of the accident and investigates the factors leading up to it. It depicts the chaos and confusion resulting from missing emergency protocol, inadequate responses of major stakeholders such as safety experts in the mine, company executives, and the political leadership at the ministry and prime ministry levels. It shows how the interplay of a culture of leniency towards mining safety, insufficient mining policies and even less effective inspections coupled with nepotism and the local population’s desperation for work, all led to serious neglect in a major mine resulting in needless deaths. The Soma Eynez Mine disaster highlights how corporate greed fed into breaches of mining protocol and ethical conduct, eventually leading to the bankruptcy of a mining conglomerate and the imprisonment of 14 men.