Improve Mine Safety Research Articles

CFD modelling of ventilation optimization for improving mine safety in longwall working faces

Mining coal seams with high coal gas content and coal spontaneous combustion (SponCom) risk is often a challenge for mining engineers. Control measures for maintaining the gas concentration under the regulation permissible limit (Generally 1%) as well as reducing coal fire risks must be taken simultaneously in order to create safety production conditions. However, in reality, such measures either for gas or for fire problems are sometimes conflictive. For an example, the basic strategy of gas control in underground is to increase the ventilation airflow for sweeping the longwall working face and diluting the gas concentration, but it also results in leakage of an amount of air into the mine gob area sufficient to support the coal SponCom development process. Conversely, sealing or isolating mine gob areas can easily cause the gas accumulation which may increase the gas explosion risk. To conquer this dilemma situation, it is necessary to deeply understand the coupling relationship between the mine gases and coal SponCom controls. In this paper, based on a real case in an underground coal mine, a ventilation parameters optimization research is conducted by using the Computational Fluid Dynamics (CFD) simulation approach for solving the stated contradiction problems to derive the optimum solutions for both managing gas hazards and fire risks in the underground. In this study, the boundary conditions are fully considered in accordance with the reality. A list of important ventilation parameters including the air quantity supplied to the mine working face, the negative ventilation pressure in the roof roadway for gas drainage and reasonable distributed airflow quantity in tailgate roadways, are investigated. The research findings balance the requirements both for gas control and fire-prevention. The proposed method could be applied to guide the mine design practices in improving safety.

Prestressed Concrete Building Coal Mine Stent Design

With the continuous development of China's coal technology, prestressed concrete stand in the coal mine construction jobs because of the building structure stiffness, mechanical characteristics, and other characteristics of joints less widely used. Firstly, the main concepts of prestressed concrete is analyzed, combined with the building of a coal mine stent design prestressed concrete examples of the main problems in the mine design process involved the stent to expand a detailed analysis and discussion, hoping to mine construction of large buildings play a guiding role in improving mine safety production conditions, to provide reliable protection for coal mine safety.

Inference of strata separation and gas emission paths in longwall overburden using continuous wavelet transform of well logs and geostatistical simulation

Abstract Prediction of potential methane emission pathways from various sources into active mine workings or sealed gobs from longwall overburden is important for controlling methane and for improving mining safety. The aim of this paper is to infer strata separation intervals and thus gas emission pathways from standard well log data. The proposed technique was applied to well logs acquired through the Mary Lee/Blue Creek coal seam of the Upper Pottsville Formation in the Black Warrior Basin, Alabama, using well logs from a series of boreholes aligned along a nearly linear profile. For this purpose, continuous wavelet transform (CWT) of digitized gamma well logs was performed by using Mexican hat and Morlet, as the mother wavelets, to identify potential discontinuities in the signal. Pointwise Holder exponents (PHE) of gamma logs were also computed using the generalized quadratic variations (GQV) method to identify the location and strength of singularities of well log signals as a complementary analysis. PHEs and wavelet coefficients were analyzed to find the locations of singularities along the logs. Using the well logs in this study, locations of predicted singularities were used as indicators in single normal equation simulation (SNESIM) to generate equi-probable realizations of potential strata separation intervals. Horizontal and vertical variograms of realizations were then analyzed and compared with those of indicator data and training image (TI) data using the Kruskal–Wallis test. A sum of squared differences was employed to select the most probable realization representing the locations of potential strata separations and methane flow paths. Results indicated that singularities located in well log signals reliably correlated with strata transitions or discontinuities within the strata. Geostatistical simulation of these discontinuities provided information about the location and extents of the continuous channels that may form during mining. If there is a gas source within their zone of influence, paths may develop and allow methane movement towards sealed or active gobs under pressure differentials. Knowledge gained from this research will better prepare mine operations for potential methane inflows, thus improving mine safety.

MODELING ATMOSPHERE COMPOSITION AND DETERMINING EXPLOSIBILITY IN A SEALED COAL MINE VOLUME

Abstract Explosions originated from or around the sealed areas in underground coal mines present a serious safety threat. The explosibility of the mine atmosphere depends on the composition of oxygen, combustible and inert gases. In additional, the composition in the inaccessible sealed areas change with time under various factors, such as gases emissions, air leakage, inert gases injected, etc. In order to improve mine safety, in this paper, a mathematical model based on the control volume approach to simulate the atmosphere compositions is developed, and the expanded Coward explosibility triangle diagram is used to assess the mine gas explosion risk. A computer program is developed to carry out the required computations and to display the results. In addition, the USBM explosibility diagram is also included in the program to serve as a double check.

A systematic approach to assess mine atmospheric status

Methane and coal dust explosions are the most feared hazards in the coal industry worldwide. The large majority of these explosions originates from or occurs around sealed mine areas. On the other hand, nearly all coal mine explosions initially start with the ignition of combustible gases such as methane, carbon monoxide, etc. Technically speaking, the explosibility of a mine atmosphere depends on the composition of oxygen, combustibles and inert gases. However, the compositions in an inaccessible sealed mine areas change with time under the influences of inflows of combustible gases, air leakage, inert gases injected, etc. In order to improve mine safety, it is desirable to have a tool to accurately simulate the gas compositions in a sealed area and to determine its explosibility. In this paper, a mathematical model to simulate atmospheric compositions in a sealed mine volume is developed, and the original Coward explosive triangle method is expanded for determining the explosibility. Finally, a case study is used to show the applicability of the developed model and the explosibility changes over time are also plotted with the help of the expanded Coward method. In addition, the USBM explosibility diagram is used to verify the results derived by the expanded Coward method.

An Organizational Social Responsibility Approach for Improving Mine Safety and Health in China

The paper aims at presenting an organizational social responsibility approach for improving mine safety and health in China. Through an in-depth comparative analysis of the regulatory mechanisms for mine safety and health in USA and South Africa, it is found that the successful performance of mine safety and health in USA has been contributed by the triangle of effective law enforcement, advanced technology development and qualified labor training, and the impressive improvement of mine health and safety in South Africa has been attributed to the mechanism of tripartite engagement through the state, mine owners and employees. In view of findings from the US and South Africa experiences, an approach of organizational social responsibility through multi-stakeholders is proposed for China to fundamentally improve its performance of mine safety and health by adopting best practices.

Flow Rate Computations in Hydraulic Fill Mine Stopes

Mining is a major industry worldwide, where hydraulic fills are commonly used for backfilling the underground voids created in the ore removal process. Hydraulic fills placed in the form of slurry drain through free draining barricades that block the access drives during the filling process. Failure of the barricades, followed by the in-rush of tailings into the mine can be catastrophic. This paper describes a simple method based on three-dimensional method of fragments, for computing the flow rates. Laboratory tests were carried out on model stopes filled with sands, and the measured flow rates compared well with those computed using the proposed method. This was also verified through numerical modelling. The proposed expressions for computing the flow rate in the three-dimensional hydraulic fill stope can be useful in the development of a spreadsheet-based fill simulation program that will help in monitoring the water level and flow rate within the stope, and improve mine safety.

Sunday Stone: an enduring metaphor of mining diseases and underground mining conditions

Abstract The occupational hazards of miners include acute trauma and death from rock falls, water inundation, explosions and the long-term effects of progressive pulmonary disease. One of the most evocative of records of the dust-laden atmosphere in which coalminers work is Sunday Stone. Specimens of Sunday Stone are preserved in the Great North Museum, the ‘Hancock’, managed by Tyne and Wear Archives and Museums in Newcastle-upon-Tyne. Sunday Stone is the name given to calcareous deposits that formed inside wooden pipes carrying wastewater from the collieries of Durham and Northumberland. Sunday Stone is composed of alternating light and dark bands, each double-band representing one 24-hour period. Water seeping into the working mines became laden with coal dust and dissolved mineral salts. The daily dark band corresponded to the working day (the ‘fore’ and ‘back’ shifts) with its heavy dust-laden atmosphere. The broader light-coloured band was laid down on Sundays during coalface downtime. Sunday Stone today comprises an enduring metaphor of the mining industry, and specimens remain as a silent but permanent witness to the conditions in which millions of underground coalminers have worked and often work today. In these banded patterns one sees the progressive struggle to improve mine safety and ventilation and the evolution of industrial preventive medicine.

China's Evolving Energy Governance: A Case Study of Mining Rights Disputes

In the foreseeable future, China will likely continue its coal-dominated energy strategy. To ensure cleaner operations, improve mining safety, and reduce greenhouse gas emissions, China has made a strong development plan to recover and utilize coalbed methane (CBM) and coalmine methane (CMM) since 2006. However, at the end of the 11th Five-Year plan in 2010, the output of CBM/CMM fell short of the planned targets. The disputes over the mining rights of CBM/CMM between local coal groups, central state-owned oil and gas companies, local governments and central governments significantly impeded development. This case study looks into these disputes and tries to unfold the complex relations between central and local actors in China’s energy governance. This report begins by introducing the background behind CBM/CMM recovery disputes and the central ministries involved in regulating or promoting CBM/CMM development. It then analyzes the historical and legal causes of disputes in Shanxi province, the attempted efforts to resolve the disputes, and the impact of the conflict on local environment and energy use. The report then discusses proposed solutions and finally gives further analysis on issues of China’s energy governance. In order to achieve its 12th Five-Year plan target in clean energy development, energy efficiency and greenhouse reduction, China should strengthen its energy and environment governance system to ensure targets will be met. Realizing a strategic policy requires serious consideration of the dynamic relations among powerful actors and the interests of local governments and the state-owned companies. It also requires new tools to improve the ability for regulators in Beijing to regulate and coordinate action on CBM/CMM.

Precursor of Thermal Power Disaster in High-Efficiency Intensifying Coal Mine and Its Early-Warning

Nowadays, the coal mine safety is still relatively vulnerable, especially with the frequent occurrence of mine thermal power disasters. Based on the characteristic of high-efficiency intensifying coal mine and the mechanism of thermal power disaster, the multi-factor coupling mechanism and process of mine thermal power disaster such as gas explosion and fire were analyzed. Meanwhile, the precursor characteristics of mine thermal power disaster and the precursor monitor and acquisition with no-blind area technology as well as such critical technology as precursor information treatment and early warning were also researched. These efforts above can help warn the serious thermal power disasters, operate the monitor equipment in advance and ensure effective warning time. All these have great significance in improving mine safety monitor and management.

Design and Realization of Mine Water-Inrush Visualization Simulation System

There exists a high risk of water-inrush in mining activities. Therefore, it is critical to develop a conceptual model of Mine Water-inrush, especially for the underground environment. The general structure of Mine Water-inrush Simulation System consists of core network, the underground monitoring network, and the operational system. Through the application of data processing system, simulation system and the application system, the original data can be processed. The results is then passed to the operators and managers, which require them increase the understanding of factors leading to accidents and consequently take action to improve mining safety. This new water-inrush model captures three characteristics to regard the mine water-inrush: the inrush sources, inrush process, and submerging process. Virtual length has been applied to the model, which is combined with a Traversal Algorithm, can be used to calculate the area of increased influence over time for each process. Based on the collected data from a real mine, the underground excavations and a virtual water-inrush disaster process were simulated, which shows that the system operates reliably.

Issues in the outburst prevention work of coal mines in Guizhou Province and the analysis of its countermeasures

In order to reduce the occurrence of coal and gas outburst accidents, and improve the capability to prevent gas hazards and realize the safe and efficient mining of coal enterprises. The distribution of the outburst coal mining area of Guizhou Province and the status of coal and gas outburst and the problems in the current outburst prevention methods were analyzed. The main issues were pointed out such as the lack of regional outburst prevention measures, unsatisfactory effect in drainage, poor management and implementation, as well as personnel that need more training. The prevention situation of coal and gas outburst in Guizhou Province was considered. In accordance with the above problems, from the perspective of strengthening geological exploration, testing coal seam parameters, studying outburst prevention technologies, deploying mining systems rationally, improving mine safety management systems, and strengthening protection facilities and other aspects, a targeted outburst prevention measure and proposals were put forward.

Discomfort Glare Comparison for Various LED Cap Lamps

Researchers at the National Institute for Occupational Safety and Health (NIOSH) are investigating different lighting technologies with the objective of improving mine safety. This paper presents the results from an ongoing study that compares discomfort glare for different light-emitting diode (LED) cap lamps using the de Boer glare rating scale. The cap lamps tested included two commercially-available LED cap lamps and one NIOSH prototype LED cap lamp tested at three different illumination levels. Prior research indicated that the NIOSH prototype enabled much better visual performance as compared to other LED cap lamps. It uses three LEDs that produce multiple illumination areas in comparison to commercially-available cap lamps that use one LED and projects a narrow spot pattern. Across subjects and cap lamp test conditions, measured illuminances (averaged at both eyes) varied from 0.62 to 3.73 lx, whereas the de Boer glare ratings varied from 4.86 to 7.71. An analysis of variance based on 15 subjects indicated a significant difference in the discomfort glare due to cap lamps (F4, 52 = 18.01, p <; 0.001). Post hoc tests indicate that one of the commercially available cap lamps exhibited lower discomfort scores, with no statistically significant differences detected between the others. Thus, the NIOSH prototype cap lamp does not cause excessive discomfort glare yet enables better visual performance.

Study on Technique of Mine Safety Management Analysis Based on Analytic Hierarchy Process

This article is based on the cognition of mine safety management, then hierarchical model of mine safety management system is built, and AHP is applied to solve the model. Then the mine safety influential factors were ordered,and the relative essentiality were made. Finally, the influence order of the assessment factors was determined. On that basis, the important influence of safety technical measures and face safety specification in mine safety management have been defined. This paper provides the foundation of mine safety management to research and helps improve mine safety management level.

Simulation of mine water inflow and gas emission during longwall mining

Reliable prediction of rock mass deformation, mine stability, mine water inflow and mine gas emission is not only essential for improving mine safety and reduction of coal production costs, but also important for the assessment of environmental impact of mining. This prediction requires the accurate simulation of complex, highly non-linear and irreversible processes including the mechanics of rock deformation and failure due to coal mining and the consequent water flow and gas desorption and flow. This paper describes a three-dimensional numerical model, called COSFLOW. It uses a Cosserat continuum approach for the efficient description of mechanical stress changes and deformation in weak layered rock, typical of coal measures. This mechanical model is coupled with a two-phase dual porosity fluid flow model to describe flow of water and gas through porous rock, desorption/adsorption of gas from the matrix and subsequent flow of water and gas through the fracture network. The coupling includes simulation of permeability and porosity changes with rock deformation. The numerical model is used to simulate water inflow and gas emission in two Australian mines. The model is calibrated using existing extensive mine water inflow and gas emission measurements and used to make predictions for future longwall panels. Comparisons of numerical predictions with later mine measurements of water inflow and gas emission demonstrate the suitability of such a code in accurately predicting mine water inflow and gas emission into a coal mine.

Improving mine safety technology and training in the U.S. recommendations of the Mine Safety Technology and Training Commission

The key issues studied focused on underground coal mining and included (1) prevention of explosions in sealed areas, (2) better emergency preparedness and response, (3) improvement of miners’ ability to escape, (4) better protection of miners before and after a fire or explosion, (5) improved provision of oxygen, and (6) development and implementation of more robust post-incident communication. The U.S. Congress passed the Mine Improvement and New Emergency Response Act of 2006, which mandated new laws to address the issues. Concurrent with investigations and congressional deliberations, the National Mining Association formed the independent Mine Safety Technology and Training Commission to study the state-of-the-art relative to technology and training that could address the vulnerabilities exposed by the mine disasters. As discussed, the report outlined persistent vulnerabilities linked with significant hazards in underground coal mines, and made recommendations to provide a path for addressing them. Overall the commission report made 75 recommendations in the areas of risk-based design and management, communications technology, emergency response and mine rescue procedures, training for preparedness, and escape and protection strategies. In its deliberations, the commission importantly noted that mine safety in the U.S. needs to follow a new paradigm for ensuring mine safety and developing a culture of prevention that supports safe production at the business core. In the commission’s viewpoint, the bottom line in protecting coal miners is not only adopting a culture of prevention but also systematically pursuing mitigation of significant risks.

Employing the underground inseam seismic method to detect old abandoned mines and improve mine safety

In July 2002, a high hydrostatic head pressure and thinner coal barrier caused a major water break that flooded the QueCreek Mine in southwest Pennsylvania. Nine miners were trapped for nearly 77 hours before they were rescued. This high-profile accident motivated the US government to investigate measures that would minimize similar accidents in the future.

High-resolution 2D surface seismic reflection survey to detect abandoned old coal mine works to improve mine safety

A serious coal mine accident in southwest Pennsylvania in July 2002 occurred when mining activity came too close to an old abandoned flooded mine. A high hydrostatic head and thin coal barrier caused a major water breakthrough and flooded the QueCreek Mine. Nine miners were trapped underground for nearly 77 hours before they could be safely rescued. This high-profile accident motivated the U.S. government to investigate and explore measures that could minimize similar accidents in the future. As a result, several groups from private companies and academia were funded to develop and demonstrate remote-sensing geophysical technologies that could detect old mine works. The focus of this study was to evaluate the potential of a high-resolution 2D surface seismic reflection survey to detect abandoned mine works near an active coal mine in Ohio.

Coalbed Methane Development: Practices and Progress in Canada

Abstract As conventional gas supplies decline, unconventional sources of gas, like coalbed methane (CBM), will become increasingly important in Canada. Canada has over 700 Tcf of CBM gas resource in place, comparable to the U.S. resource. Canada now has the world's largest "dry" coal play and it is estimated (as shown below) that CBM will grow to 2 - 3 Bcf/d in production over the next 10 – 20 years and lead to recovery of up to 75 Tcf of gas. Since 2000, increased drilling activity has led to over 3,000 CBM wells and 150 MMcf/d of CBM production in Canada today, with both estimated to grow substantially in 2005 and beyond. CBM will become an increasingly important part of Canada's gas supply. Introduction Coalbed methane (CBM) is simply the natural gas that is generated by coal seams during the coalification process. It is "sweet gas" (not sour), is largely comprised of methane (&amp;gt;90%), and is similar to the natural gas that is burned in homes. In Alberta, the Department of Energy (DOE) refers to CBM as natural gas from coal, or NGC, to associate it with existing regulations which govern the production of natural gas. In British Columbia (BC), it is referred to by the Ministry of Energy and Mines (MEM) as coalbed gas, or CBG. Regardless of the name used, it is the same gas. CBM reservoirs are classified as "unconventional" and have gas storage and production mechanisms that distinguish them from conventional reservoirs. Most of the gas in coal is stored in a sorbed state within the coal matrix, physically attached to the complex internal surfaces of the coal as a function of pressure, characterized by sorption isotherms(1, 2). Coals which are suitable for CBM production are naturally fractured, with closely spaced natural fractures, or "cleats," which provide pathways for gas flow from the coal matrix. In many cases, but not all, these cleats are initially full of water, which must be produced to reduce the pressure around the coal matrix allowing the sorbed gas to desorb and become free gas which can then be produced. The gas storage and production mechanisms of coals are comprehensively covered in References (1) and (2) and elsewhere in the oil and gas literature. In Canada, commercial production of CBM has only recently begun. The objective of this paper is to provide a summary of the major coal groups being targeted for development in Canada and an update on the recent evaluation and development. Predictions of future performance will also be presented. CBM History in the U.S. Commercial development of CBM began in the U.S. in the 1980s. Initial efforts to remove the gas from coals were funded by the U.S. Bureau of Mines primarily to improve mine safety. As natural gas value increased, the research began to focus on capturing the CBM for commercial use, and hundreds of millions of dollars were dedicated to research and development projects by the U.S. DOE, the Gas Research Institute (GRI), and the industry(3–7).

Simulation of CO 2 sequestration in coal beds: The effects of sorption isotherms

For over 30 years, horizontal wells have been drilled into coal seams to release trapped methane and improve mine safety. For more than two decades, significant quantities of gas sorbed in coal seams have been collected as a relatively environmentally friendly fossil fuel energy resource. Laboratory experiments have shown that coals preferentially sorb carbon dioxide. Thus, concomitant enhanced coal bed methane production and carbon dioxide sequestration in unminable coal seams is a promising technology being developed as a win–win process to reduce global warming and produce a valuable energy resource. However, because CO 2 will not reach all portions of the seam, not all of the in situ methane will be produced and not all of the “theoretical” sequestration capacity will be utilized. For sequestration, the amount of carbon dioxide that could be stored in the coal seam was found to be between 50% and 70% of the thermodynamic limit. The fraction of methane produced was much higher, between 80% and 97%. Reservoir simulations were used to predict how the well pattern and operating conditions can be modified to maximize the amounts of CO 2 stored and CH 4 recovered. For this study, we used the PSU-COALCOMP compositional coal bed methane reservoir simulator and measured sorption isotherms to predict the maximum amount of carbon dioxide that could be sequestered in a coal seam and show how coal seam characteristics and injection practices will reduce the actual amount sequestered.