Greenhouse gas emissions from shallow uncovered coal seams

This study discusses a method of quantifying emissions from surface coal mining that has been trialled in Australia. The method is based on direct measurement of surface emissions from uncovered coal seams in mine pits, concurrent measurement of residual gas content of blasted coal in mine pits, and measurement of pre-mining gas content of the same seam from cores retrieved from exploration boreholes drilled away from active mining. The results from one of the mines studied are presented in this paper. In this mine, the pre-mining gas content of the target seam was measured using cores from an exploration borehole away from active mining. Gas content varied from 0.7 to 0.8 m³/t and gas composition varied from 16% to 21% CH₄ (84–79% CO₂). In-pit measurements included seam surface emissions and residual gas content of blasted and ripped coal. Residual gas content varied from 0.09 to 0.15 m³/t, less than twofold across the mine pit. Composition of the residual gas was in general 90% CO₂ and 10% CH₄, with slight variation between samples. Coal seam surface emissions varied from 1.03 to 7.50 mL of CO₂-e per minute and per square meter of the coal seam surface, a sevenfold variation across the mine pit.     

Analysis of diffusion behavior of harmful emissions from trackless rubber-wheel diesel vehicles in underground coal minesOA

To define the diffusion behavior of harmful exhaust substances from diesel vehicles and support safety risk assessments of underground coal mines, we performed a multi-species coupling calculation of the emission and diffusion of harmful substances from a trackless rubber-wheel diesel vehicle. A computational fluid dynamics(CFD) model of the diffusion of harmful emissions was hence established and verified. From the perspective of risk analysis, the diffusion behavior and distribution of hazardo...     

采煤工作面瓦斯涌出量的灰色建模及预测研究

矿井瓦斯涌出量预测是新建矿井和改扩建矿井通风设计、安全管理、制定合理的瓦斯防治措施必不可少的重要环节,瓦斯涌出量预测精度的高低直接决定着矿井生产时的安全程度、经济效益的好坏,因此,瓦斯涌出量预测一直是国内外学者十分关注的研究课题.长期以来,我国一直沿用传统的矿山统计法和瓦斯含量法来预测矿井瓦斯涌出量,这两种预测方法都有各自的适用条件和局限性.本文介绍一种新的瓦斯涌出量预测方法———灰色非定空预测法的原理及应用.实践表明:利用该法能迅速、准确地对"贫息"的预测区(包括新矿区)进行瓦斯涌出量预测.     

Developing coal burst propensity index method for Australian coal mines

Coal burst is the violent failure of overstressed coal, and it is often accompanied by sound, coal ejection and seismic events. It is subsequently recognized as a serious safety risk of Australia after double fatalities coal burst happened at Austar Coal Mine. Considering the increasing trend of coal burst severity and frequency with mining depth, it is an urgent task to develop the coal burst risk assessment methods for Australia underground coal mines. Coal burst propensity index method is a widely used method of burst risk evaluation of coal as it is summed up from the coal burst research and practice of many countries.This paper presents the experimental and theoretical research of coal burst propensity index method for coal burst risk assessment in Australia. The definition of four indexes including elastic strain energy index(W_(ET)), bursting energy index(K_E), dynamic failure time(DT) and uniaxial compression strength(RC)is introduced in the first part. Then, the standard laboratory test process and test parameter of coal burst propensity index is presented. DT test is conducted with 0.3 mm/min displacement control loading rate while other test is with 0.5 mm/min. Besides, modified data processing and risk classification method of test are proposed. Differentiate analysis of stress-strain curve is adopted in the data processing of DT and KEindex. A four level risk classification form of burst risk is recommended for Australian underground coal mines. Finally, two likely improvement methods of W_(ET) test, including volumetric strain indicator method and theoretical calculation method, are discussed.     

Quantitative hazard assessment for Zonguldak Coal Basin underground mines

Underground coal mining is one of the most dangerous occupations throughout the world. The reasons behind an underground occupational accident are too complex to analyze mainly due to many uncertainties which may arise from geological, operational conditions of the mine or individual characteristics of employees. This study proposes implementing a quantitative methodology for the analysis and assessment of hazards associated with occupational accidents. The application of the proposed approach is performed on the mines of Turkish Hard Coal Enterprises(TTK). The accidents in TTK between the years 2000 and 2014 are firstly statistically analyzed with respect to the number, type and location of accidents, age,experience, education level and main duty of the casualties and also injuries resulting from such accidents. The hazards are classified as individual, operational and locational hazards and quantified using contingency tables, conditional and total probability theorems. Lower and upper boundaries of hazards are determined and event trees for each hazard class are prepared. Total hazard evaluation results show that Armutcuk, Karadon and Uzulmez mines have relatively high hazard levels while Amasra and Kozlu mines have relatively lower hazard values.     

高瓦斯矿井一次采全高综采工作面瓦斯治理

介绍了晋城矿区寺河矿高瓦斯矿井一次采全高工作面瓦斯治理方法和瓦斯利用情况,提出了高瓦斯矿井一次采全高工作面瓦斯治理途径和技术,指出高瓦斯矿井高产高效、安全生产的根本出路在于提高瓦斯抽放率,加强瓦斯利用,进而提高矿井的综合效益.     

A semi-quantitative coal burst risk classification system

Safety is the highest priority in the mining industry as underground mining in particular poses high safety risks to its workers. In underground coal mines, coal bursts are one of the most catastrophic hazards, which involves sudden and violent dynamic coal mass failure with rapid ejection of the broken material into the mine workings. Despite decades of research, the contributing mechanisms of coal bursts are still not completely understood. Hence, it remains challenging to forecast coal bursts and quantify their likelihood of occurrence. However, a range of geological and geotechnical factors are associated with coal bursts and can increase the coal burst proneness. This paper introduces a semi-quantitative coal burst risk classification system, namely, BurstRisk. Based on back-analysis of case histories from Australia, China and the United States, BurstRisk classifies the coal burst risk into three categories:low, medium and high risk. In addition, it allows mining engineers to modify the weighting of the selected factors based on specific conditions. The risk classification charts introduced are for both longwall retreat and development sections of long-wall mining operations. This paper also provides a set of risk management strategies and control measures for effective coal burst mitigation.     

Computer simulation of evacuation in underground coal mines

In order to study the evacuation behavior of miners during accidents,we analyzed the rational layout of a safe chamber,and improved evacuation efficiency.A visual model of evacuation was developed and used to simulate the evacuation process of mines,given their special underground environments.In our simulation,the working faces of a coal mine and nearby tunnels were divided into 0.5 m×0.5 m grids to reflect the location of occupants and obstacles.Based on a"flow potential of the occupant",we determined the direction of movement and routes of occupants.In the model,evacuation speed changed as a function of crowd density,with an average speed of 1.30 m/s.The model also takes into account detection time of the disaster and the personnel response time.Evacuation time,exit flow rate and evacuation path were obtained by simulation.The results indicate that using simulation technology can present a more visual evacuation process and show the behavior of occupants.Our establishment of a mine safety evacuation system has merit as reference value.     

河北省煤矿区瓦斯赋存构造控制

通过对河北省7个煤与瓦斯突出矿井、12个高瓦斯矿井、32个低瓦斯矿井煤矿区瓦斯地质特征的研究,提出了河北省瓦斯赋存构造逐级控制理论,华北板块构造控制河北省瓦斯分布,区域构造控制各矿区瓦斯分布,矿井构造控制采区、采面瓦斯.厘定出开平煤田北西翼高突带、下花园八宝山高突带、邯邢煤田鼓山东侧深部高瓦斯带和兴隆-宽城-松树台高瓦斯带4个高瓦斯带.研究表明:河北省内煤矿区高突瓦斯矿井的分布受控于EW向燕山褶皱带和NNE太行山构造带两大构造带,具有分带特征,太行山东麓的瓦斯由于深大断裂和地下水的控制而呈现"西低东高,南小北大"的态势,燕山褶皱带受燕山期NW-SE向水平挤压作用发育有逆冲推覆构造,密集发育的逆断层造成煤层叠瓦式分布有利于瓦斯的保存,80%矿井含煤地层集中在石炭二叠系,石炭二叠系瓦斯突出危险性要比侏罗系煤层大.     

Application of coal mine roof rating in Chinese coal mines

The coal mine roof rating(CMRR) is a measure of roof quality or structure competency for bedded roof types typically of underground coal mines. The CMRR has been used widely in the US, South Africa,Canada and Australia. In order to investigate the application of the CMRR system in Chinese coal mines,two coal mines in China located in Panjiang Coal Field in Guizhou Province were investigated. Field data were collected which is required to calculate the CMRR value based on underground exposure. The CMRR values of 11 locations in two coal mines were calculated. The investigations demonstrated that the chance of mine roof failure is very low if the CMRR value is more than 50, given adequate support is installed in mine. It was found that the CMRR guideline are useful to preliminarily investigate stability in Panjiang Coal Field mines.     

煤矿井下无火花截割机的研制

煤矿井下地质复杂 ,条件恶劣 ,常有事故和故障发生 .当紧急排除故障时 ,需要对被堵地段进行疏通和清理 ,为此 ,研制了一种无火花截割机进行快速疏通 ,该机的主机部分为经过优化设计的曲柄摇块机构 .经井下试验表明 :该机设计合理、简单实用 ,是煤矿井下尽快排除故障或打开一条救生通道时可选用的一种先进设备     

Review of coal and gas outburst in Australian underground coal mines

Outburst of coal and gas represents a significant risk to the health and safety of mine personnel working in development and longwall production face areas. There have been over 878 outburst events recorded in twenty-two Australian underground coal mines. Most outburst incidents have been associated with abnormal geological conditions.Details of Australian outburst incidents and mining experience in conditions where gas content was above current threshold levels are presented and discussed. Mining experience suggests that for gas content below 9.0 m³/t, mining in carbon dioxide (CO₂) rich seam gas conditions does not pose a greater risk of outburst than mining in CH₄ rich seam gas conditions. Mining experience also suggests that where no abnormal geological structures are present that mining in areas with gas content greater than the current accepted threshold levels can be undertaken with no discernible increase in outburst risk. The current approach to determining gas content threshold limits in Australian mines has been effective in preventing injury from outburst, however operational experience suggests the current method is overly conservative and in some cases the threshold limits are low to the point that they provide no significant reduction in outburst risk. Other factors that affect outburst risk, such as gas pressure, coal toughness and stress and geological structures are presently not incorporated into outburst threshold limits adopted in Australian mines. These factors and the development of an outburst risk index applicable to Australian underground coal mining conditions are the subject of ongoing research.     

Bayesian discriminant analysis for prediction of coal and gas outbursts and application

Based on the principle of Bayesian discriminant analysis, we established a model of Bayesian discriminant analysis for predicting coal and gas outbursts. We selected five major indices which affect outbursts, i.e., initial speed of methane diffusion, a consistent coal coefficient, gas pressure, destructive style of coal and mining depth, as discriminating factors of the model. In our model, we divided the type of coal and gas outbursts into four grades regarded as four normal populations. We then obtained the corresponding discriminant functions through training a set of data from engineering examples as learning samples and evaluated their criteria by a back substitution method to verify the optimal properties of the model. Finally, we applied the model to the pre-diction of coal and gas outbursts in the Yunnan Enhong Mine. Our results coincided completely with the actual situation. These results show that a model of Bayesian discriminant analysis has excellent recognition performance, high prediction accuracy and a low error rate and is an effective method to predict coal and gas outbursts.     

九里山矿14区放顶煤开采瓦斯涌出规律分析

分析了焦作矿务局九里山矿放顶煤工作面沿底掘进及开采期间各生产工序瓦斯涌出规律． 与顶分层开采对比, 放顶煤开采相对瓦斯涌出量降低, 绝对瓦斯涌出量增加倍数小于产量提高倍数, 各生产工序以放煤时瓦斯涌出量最大; 沿顶掘巷的平均瓦斯涌出量是沿底掘巷的１ ．２５ 倍, 沿底掘进不增加突出危险性     

A general solution and approximation for the diffusion of gas in a spherical coal sample

The square root relationship of gas release in the early stage of desorption is widely used to provide a simple and fast estimation of the lost gas in coal mines. However, questions arise as to how the relationship was theoretically derived, what are the assumptions and applicable conditions and how large the error will be. In this paper, the analytical solutions of gas concentration and fractional gas loss for the diffusion of gas in a spherical coal sample were given with detailed mathematical derivations based on the diffusion equation. The analytical solutions were approximated in case of small values of time and the error analyses associated with the approximation were also undertaken. The results indicate that the square root relationship of gas release is the first term of the approximation, and care must be taken in using the square root relationship as a significant error might be introduced with increase in the lost time and decrease in effective diameter of a spherical coal sample.     

煤盆地中的新生天然气资源

人类长期的采煤活动,打破了地下应力的原始平衡状态,形成了十分发达的地下裂隙网络,以致含煤盆地中可采与不可采煤层中的煤层气和老塘瓦斯气等可燃气体,借以发生新的运移,甚至泄漏于地表.在盖层条件具备的情况下,发生新运移的煤成气可能形成层、带状分布的新生天然气资源.这种新生天然气既是老煤矿区(甚至废弃矿区)特有的、可供开发利用的气体矿产,也是造成地质灾害的温室气体.     

Analysis of underground fires in Polish hard coal mines

In the period of the first twenty years after World War II the number of fires in Polish hard coal mines reached annually the value of several thousands of cases. About 80% of fires constituted spontaneous fires. Investigations into the development of new methods of fire hazard prediction and implementation of new methods and means of fire prevention as well as the introduction of prohibition concerning the use of products manufactured of combustible organic materials in underground mine workings re-duced considerably the hazard of underground fire rise. The worked out at the Central Mining Institute (GIG) new method of un-derground fire prediction allows the correct selection of fire prevention means. The introduction into common use of fire-resistant conveyor belts, the main factor giving rise to spontaneous fires, and methods of assessment of their fire resistance eliminated prac-tically the fire hazard. These activities contributed in an efficient way to the reduction of the number of underground fires to a sa-tisfactory level.     

Effect of protective coal seam mining and gas extraction on gas transport in a coal seam

A gas–solid coupling model involving coal seam deformation,gas diffusion and seepage,gas adsorption and desorption was built to study the gas transport rule under the effect of protective coal seam mining.The research results indicate:(1) The depressurization effect changes the stress state of an overlying coal seam and causes its permeability to increase,thus gas in the protected coal seam will be desorbed and transported under the effect of a gas pressure gradient,which will cause a decrease in gas pressure.(2) Gas pressure can be further decreased by setting out gas extraction boreholes in the overlying coal seam,which can effectively reduce the coal and gas outburst risk.The research is of important engineering significance for studying the gas transport rule in protected coal seam and providing important reference for controlling coal and gas outbursts in deep mining in China.     

Illumination of parameter contributions on uneven break phenomenon in underground stoping mines

One of the most serious conundrum facing the stope production in underground metalliferous mining is uneven break(UB: unplanned dilution and ore-loss). Although the UB has a huge economic fallout to the entire mining process, it is practically unavoidable due to the complex causing mechanism. In this study,the contribution of ten major UB causative parameters has been scrutinised based on a published UB predicting artificial neuron network(ANN) model to put UB under the engineering management. Two typical ANN sensitivity analysis methods, i.e., connection weight algorithm(CWA) and profile method(PM) have been applied. As a result of CWA and PM applications, adjusted Q rate(AQ) revealed as the most influential parameter to UB with contribution of 22.40% in CWA and 20.48% in PM respectively. The findings of this study can be used as an important reference in stope design, production, and reconciliation stages on underground stoping mine.     

Fundamentals of modern ground control management in Australian underground coal mines

Underground coal mining is inherently hazardous, with uncontrolled ground failure regarded as one of only several critical risks for multiple fatality events. Development, implementation and management of overarching systems and procedures for maintaining strata control is an important step to mitigating the impact of ground failure hazards at a mine site operational level. This paper summarised the typical pro-active ground control management system(PGCMS) implemented in various Australian underground coal mines. Australia produces approximately 100 million tonnes a year of metallurgical and thermal coal from approximately 30 of the world's safest longwall mines operating in New South Wales and Queensland. The increased longwall productivity required to achieve both high levels of safety and profitability, places significant emphasis on the reliability of pro-active ground control management for longwall mining operations. Increased depths, adverse geological conditions, elevated variable stress regimes and weaker ground conditions, coupled with an industry wide need for increased development rates continue to make ground control management challenging. Ground control management is not only about ground support and pillar design though but also a structured process that requires a coordinated effort from all levels of the workforce to both minimise the occurrence of adverse geotechnical events and mitigate the potential risks when they do occur. The PGCMS presented in this paper is proven to provide both a safer and more productive mine environment through minimisation of unplanned delays. The critical elements of the method are presented in detail and demonstrate the utility and value of a ground control management system that has potential for implementation in underground coal mining globally.