Study on overburden failure law and surrounding rock deformation control technology of mining through fault.

In the mining process of working face, the additional stress generated by the fault changes the law of roadway deformation and failure as well as the law of overburden failure. Aiming at the influence of the fault in the mining process of working face, this study introduced the geological strength index (GSI) to analyze the stress distribution in the elastic-plastic zone of the surrounding rock of the roadway. And similar experiments under different engineering backgrounds were combined to study the characteristics of overburden movement and stress evolution. Based on the conclusions obtained, the roadway support scheme was designed. This study shows that, compared with ordinary mining, through-the-fault mining causes slippage and dislocation of the fault, the load of the overburden is transferred to both sides of the fault, and the stress near the fault accumulates abnormally. The "three zones" characteristics of the overburden movement disappear, the subsidence pattern is changed from "trapezoid" to "inverted triangle", and the influence distance of the advanced mining stress on the working face is extended from 20m to 30m. The instability range of roadway surrounding rock is exponentially correlated with the rupture degree of the surrounding rock. Through the introduction of GSI, the critical instability range of roadway surrounding rock is deduced to be 2.32m. According to the conclusion, the bolt length and roadway reinforced support length are redesigned. Engineering application shows that the deformation rate of the roadway within 60 days is controlled below 0.1~0.5mm/d, the deformation amount is controlled within 150mm, and the roadway deformation is controlled, which generally meets the requirements of use. The research results provide guidance and reference for similar roadway support.

An experimental investigation into the borehole drilling and strata characteristics.

Measurement while drilling is an important part of the intelligent development of coal mines. The main purpose of this paper is to comprehensively analyze the response characteristics of borehole drilling parameters and find a better method to predict rock mechanical properties based on drilling parameters. Firstly, six concrete blocks and multiple specimens were prepared with different material ratios. Next, the concrete specimens were tested for mechanical properties in the laboratory. Meanwhile, the displacement, rotation speed, torque, and sound pressure level (SPL) were observed during the drilling of the concrete blocks. Finally, the response characteristics of drilling parameters such as rotation speed, rate of penetration (ROP), torque, and SPL were analyzed. Besides, multiple prediction models of rock mechanical parameters were obtained by data analysis. The research results indicate that the drilling process can be classified into the initial stage of drilling (fast speed) and the steady stage of drilling (slow speed). The torque work ratio accounts for more than 99%, which increases with the increase in rock strength. The penetration depth per revolution and torque work ratio are significantly related to rock uniaxial compressive strength, Brazilian tensile strength, cohesion, and elastic modulus. The ROP is the best choice for estimating rock mechanical parameters. This research provides an important reference for laboratory rock mechanics parameter testing and geological features detection based on drilling parameters.

Dynamic fracture mechanics and energy distribution rate response characteristics of coal containing bedding structure.

To investigate the influence of bedding structure and different loading rates on the dynamic fracture characteristics and energy dissipation of Datong coal, a split Hopkinson bar was used to obtain the fracture characteristics of coal samples with different bedding angles. The process of crack initiation and propagation in Datong coal was recorded by the high-speed camera. The formula for the model I fracture toughness of the transversely isotropic material is obtained on the basis of the finite element method (FEM) together with the J-integral. By comparing the incident energy, absorbed energy, fracture energy and residual kinetic energy of Datong coal samples under various impact speeds, the energy dissipation characteristics during the dynamic fracture process of coal considering the bedding structure is acquired. The experimental results indicate that the fracture pattern of notched semi-circular bending (NSCB) Datong coal is tensile failure. After splitting into two parts, the coal sample rotates approximately uniformly around the contact point between the sample and the incident rod. The dynamic fracture toughness is 3.52~8.64 times of the quasi-static fracture toughness for Datong coal. Dynamic fracture toughness increases with increasing impact velocity, and the effect of bedding angle on fracture toughness then decreases. In addition, the residual kinetic energy of coal samples with the same bedding angle increases with the increase of impact speed. The energy utilization rate decreases continuously, and the overall dispersion of statistical data decreases gradually. In rock fragmentation engineering, the optimum loading condition is low-speed loading regardless of energy utilization efficiency or fracture toughness. These conclusions may have significant implications for the optimization of hydraulic fracturing process in coal mass and the further understanding of crack propagation mechanisms in coalbed methane extraction (CME). The anisotropic effect of coal should be fully considered in both these cases.

Constraints of coal mining safety management efficiency.

BACKGROUND: Investigation of the safety management efficiency in a coal mine aims to improve its safety management level thus ensuring coal mining safety. However, the safety management efficiency is affected by many factors especially for those coal mines operated underground. Furthermore, the constraint factors that are difficult to be identified and eliminated may impede safety management efficiency. OBJECTIVE: This work aims to explore the constraints affecting safety management efficiency through a mathematical model accompanied by some effective measures guided by the theory of constraint (TOC). METHODS: An index system for coal mining safety management efficiency (CMSME) is first established. Then a mathematical model roughly identifying the constraint factors is constructed. The principle of the proposed model is a comparison with the changes of the ratio of integrated CMSME and the ratio of each impact factor over a certain period. Thus, a constraint factor may be one whose ratio changes at a slower rate than that of the integrated CMSME. Following this, some measures are adopted to identify one, or more, real constraints. Finally, the constraints may be broken by internal, or external, means. RESULTS: A case study from Quandian coal mine verified the proposed method: the constraints affecting CMSME could be identified and broken through during the production. This research currently is applied to coal mining activities in a few coal mines, and it will be widely used in the future. CONCLUSIONS: This paper provides a novel method investigating the constraints affecting CMSME and breaking through them. The case study shows that breaking through constraints during the production is beneficial to CMSME. Furthermore, a coal mine with a high CMSME index may still, at some time, have one, or more, bottleneck constraints.

Coal mining and lung disease in the 21st century.

PURPOSE OF REVIEW: To review the impact of coal mining and resurgence of coal workers' pneumoconiosis (CWP) in 21st century and effect of ambient air pollution on lung function. RECENT FINDINGS: At the beginning of 21st century, statistics by National Institute for Occupational Safety and Health showed a steep rise in pneumoconiosis. This was followed by numerous epidemiologic and pathologic studies that confirmed increasing CWP prevalence as well as disease in younger miners and those with a shorter mining tenure. Recent studies have demonstrated that poor dust control in mines, a relative shift in composition of the coal mine dust, small sized mines and increase in surface mining are all possible contributors to this resurgence. There is also growing literature evaluating the effects of worsening air pollution on health, including decreasing lung function and development of emphysema, worsening quality of life measures and lung cancer. SUMMARY: This irreversible but preventable disease currently haunts approximately 60 000 miners across United States and millions across the world. Its resurgence despite the strict dust regulations is a setback from the public health standpoint. The continued reliance on coal for energy will continue to place coal miners at danger of developing disease as well as the world.

Fuzzy risk assessment for mechanized underground coal mines in Turkey.

The decision matrix method is preferred as a measure of risk evaluation considering the risk value obtained by two risk factors such as the likelihood and severity of a hazard. However, it has some deficiencies since a crisp risk score is assigned for likelihood and severity. In this article, a fuzzy logic-based safety evaluation method to enhance the risk assessment process is introduced to overcome the uncertainties encountered in the classical decision matrix risk assessment method. The proposed method is a more realistic evaluation of the risks which may be available in mechanized coal mines in Turkey. In this way, risky situations and operations in mechanized underground coal mines have been determined by expert knowledge and engineering judgement in linguistic forms. Thus, such an evaluation will be a valuable guide for coal mines in which fully mechanized coal production is expected in the near future.

Research on complex air leakage method to prevent coal spontaneous combustion in longwall goaf.

Spontaneous combustion of coal is one of the major hazards threatening production safety during longwall mining. Mining-induced voids, which provide passages for air leakage, are the key factor triggering spontaneous combustion of coal in longwall goafs. In this study, a comprehensive method, which combined pressure balance, grouting injection, and filling fissures, was proposed to prevent spontaneous combustion of coal in longwall goafs with complex air leakage. Field engineering practice was carried out in Sitai Coal Mine in China. The results demonstrated that with the application of the proposed method, in the working face, the concentration of CO was decreased from 31ppm to 0 and the air leakage quantity was decreased from 261 to below 80 m3min-1. The gas samples analysis from the gob areas also indicated that concentrations of O2 and CO were successively decreased, indicating that the risk of spontaneous combustion of coal in goafs was eliminated. The above mentioned analysis indicates that, the method proposed in this study is useful and efficient. Successful application of this technology could provide reference for the treatment of other coal mines.

Relevance Proof of Safety Culture in Coal Mine Industry.

This paper intends to use data to verify the correlation between safety culture, safety management system and safety knowledge, safety awareness, and safety habits, which is the correlation between the various parts of the behavior safety "2-4" model. Due to data limitations, the results are limited to the study of safety culture related relationships in coal mining enterprises. This paper first designed a questionnaire containing 30 questions, of which 1⁻5 questions represent safety culture, 6⁻22 questions represent safety management system, and 23⁻30 questions represent safety knowledge, safety awareness and safety habits. Employees of 27 coal mining enterprises in Shandong, Henan, Hunan and other places in China were surveyed and sampled by stratified random sampling, and 1514 valid questionnaires were obtained. After item analysis and correlation analysis, and it was found that, within the data of 1514 questionnaires, the item total correlation coefficients of questions 6, 9, 19 and 28 were all less than 0.2, indicating that the identification degree of these four items was poor, which was deleted. Using the data analysis of the remaining 26 questions in the questionnaire, it was found that the relationship between safety culture and the safety management system, the safety management system and safety knowledge, and safety awareness and safety habits is moderately related; safety culture and safety knowledge, safety awareness and safety habits are weakly related. The conclusion shows that the safety culture directly affects the safety management system; the safety management system directly affects the safety knowledge, safety awareness and safety habits; the safety culture indirectly affects safety knowledge, safety awareness and safety habits. However, why the expected strong correlation is not achieved, and whether the same conclusion can be obtained if the data scale is expanded or other types of enterprises are added for questionnaire measurement, these are questions worthy of further study, which is also the author's next research content.

A systems approach to extraordinarily major coal mine accidents in China from 1997 to 2011: an application of the HFACS approach.

This study aimed to provide a greater understanding of the systemic factors involved in coal mine accidents and to examine the relationships between the contributing factors across all levels of the system. Ninety-four extraordinarily major coal mine accidents that occurred in China from 1997 to 2011 were analyzed using the human factors analysis and classification system (HFACS). The empirical results showed that the frequencies of unsafe behaviors, inadequate regulation and failure to correct hidden dangers were the highest among five levels, 14 categories and 48 indicators, respectively. The odds ratio technique was applied to quantitatively examine the relationships between contributing factors. Various statistically significant associations were discovered and should receive greater attention in future attempts to develop accident measures. In addition, several strategies concerning the main contributing factors and routes to failure are proposed to prevent accidents from reoccurring in an organization.

Geospatial analysis of residential proximity to open-pit coal mining areas in relation to micronuclei frequency, particulate matter concentration, and elemental enrichment factors.

During coal surface mining, several activities such as drilling, blasting, loading, and transport produce large quantities of particulate matter (PM) that is directly emitted into the atmosphere. Occupational exposure to this PM has been associated with an increase of DNA damage, but there is a scarcity of data examining the impact of these industrial operations in cytogenetic endpoints frequency and cancer risk of potentially exposed surrounding populations. In this study, we used a Geographic Information Systems (GIS) approach and Inverse Distance Weighting (IDW) methods to perform a spatial and statistical analysis to explore whether exposure to PM2.5 and PM10 pollution, and additional factors, including the enrichment of the PM with inorganic elements, contribute to cytogenetic damage in residents living in proximity to an open-pit coal mining area. Results showed a spatial relationship between exposure to elevated concentrations of PM2.5, PM10 and micronuclei frequency in binucleated (MNBN) and mononucleated (MNMONO) cells. Active pits, disposal, and storage areas could be identified as the possible emission sources of combustion elements. Mining activities were also correlated with increased concentrations of highly enriched elements like S, Cu and Cr in the atmosphere, corroborating its role in the inorganic elements pollution around coal mines. Elements enriched in the PM2.5 fraction contributed to increasing of MNBN but seems to be more related to increased MNMONO frequencies and DNA damage accumulated in vivo. The combined use of GIS and IDW methods could represent an important tool for monitoring potential cancer risk associated to dynamically distributed variables like the PM.

Establishment and application of an index system for prevention of coal workers' pneumoconiosis: a Delphi and analytic hierarchy process study in four state-owned coal enterprises of China.

OBJECTIVE: To explore the difference of cumulative incidence rate of coal workers' pneumoconiosis (CWP) among four large state-owned coal enterprises in northern China, we created an index system for evaluating the quality of comprehensive measures against CWP and applied the system to evaluate and compare the measures of the four coal enterprises. METHODS: A two-round Delphi investigation was conducted to identify the indicators in the index system. The weight values of the indicators were calculated with analytic hierarchy process methods. Measures of CWP, mine annals, records and other information in each coal mine of the four enterprises were collected. The evaluation scores, which ranged from 0 to 100, were calculated and compared with. RESULTS: A three-grade index system with 3 first-grade indicators, 9 second-grade indicators and 44 tertiary-grade indicators was established. The expert authority coefficient (Cr ) was 0.75 and the Kendall's coefficient of concordance (Kendall's W) was 0.15 (χ2=193.30, P<0.001). The weight value of 'Geological conditions' was 0.43, equal to 'Dust control engineering technology', and that of 'Occupational health management' was 0.14. The medians and quartiles of the evaluation scores of comprehensive measures against CWP of the four enterprises were 58.38 (54.60~63.02), 64.63 (60.83~67.06), 72.99 (68.92~77.67) and 75.07 (70.73~79.20), respectively. CONCLUSIONS: The index system could be effectively used for evaluation and comparison of the comprehensive measures against CWP among different enterprises. The geological conditions and dust control engineering technology played an important role in preventing and controlling CWP.

A risk-based decision support framework for selection of appropriate safety measure system for underground coal mines.

In the context of underground coal mining industry, the increased economic issues regarding implementation of additional safety measure systems, along with growing public awareness to ensure high level of workers safety, have put great pressure on the managers towards finding the best solution to ensure safe as well as economically viable alternative selection. Risk-based decision support system plays an important role in finding such solutions amongst candidate alternatives with respect to multiple decision criteria. Therefore, in this paper, a unified risk-based decision-making methodology has been proposed for selecting an appropriate safety measure system in relation to an underground coal mining industry with respect to multiple risk criteria such as financial risk, operating risk, and maintenance risk. The proposed methodology uses interval-valued fuzzy set theory for modelling vagueness and subjectivity in the estimates of fuzzy risk ratings for making appropriate decision. The methodology is based on the aggregative fuzzy risk analysis and multi-criteria decision making. The selection decisions are made within the context of understanding the total integrated risk that is likely to incur while adapting the particular safety system alternative. Effectiveness of the proposed methodology has been validated through a real-time case study. The result in the context of final priority ranking is seemed fairly consistent.

The Safety Attitudes of Senior Managers in the Chinese Coal Industry.

Introduction: Senior managers' attitudes towards safety are very important regarding the safety practices in an organization. The study is to describe the current situation of senior managers' attitudes towards safety in the Chinese coal industry. Method: We evaluated the changing trends as well as the reasons for these changes in the Chinese coal industry in 2009 and in 2014 with 168 senior manager samples from large Chinese state-owned coal enterprises. Evaluations of 15 safety concepts were performed by means of a questionnaire. Results and Conclusions: Results indicate that, in 2014, three concepts were at a very high level (mean > 4.5), and six were at a relatively high level (4.5 > mean > 4.0). Analyses of changing trends revealed that nine concepts improved significantly, while four greatly declined in 2014 compared to those in 2009. The data reported here suggest that the reasons for the significant improvement with respect to the nine concepts include the improvement in social and legal environments, the improvement of the culture of social safety, workers' safety demands being met, and scientific and technical advances in the coal industry. The decline of the four concepts seemed to be caused by a poor awareness of managers in the coal industry that safety creates economic benefits, insufficient information on safety, inadequate attention to the development of a safety culture and safety management methods, and safety organizations and workers' unions not playing their role effectively. Practical Applications: We therefore recommend strengthening the evidence that safety creates economic benefits, providing incentives for employees to encourage their participation in safety management, and paying more attention to the prevention of accidents in coal mines via safety organizations and unions. These results can provide guidelines for workers, industrialists, and government regarding occupational safety in the whole coal industry.

[IDENTIFICATION OF OCCUPATIONAL RISK FOR ARTERIAL HYPERTENSION. REPORT II: ELIMINATION OF THE MODIFYNG INFLUENCE OF FACTORS OF CARDIOVASCULAR RISK].

This study is a continuation of (Report I) identification of the occupational risk of arterial hypertension (AH) in 13 occupational groups (3842 workers, men). In previous work there was eliminated the influence of traditional factors of the cardiovascular risk, in this study there was implemented the identification of the components of a healthy worker effect (HWE) and the elimination of their influence on the occupational risks of hypertension. Identification and removal of components HWE--the effect of a healthy recruitment (EHR) and the effect of the healthy worker persisting to work (EHWPW--was carried out by the analytic rearranging of the standardized for age and obesity prevalence rate of arterial hypertension with the use of own methodological approaches. For the determination of the presence and severity of EHR there was performed an analysis of the initial prevalence rate of arterial hypertension in the youngest age groups (under 31 years). To overcome HER standardized for age and obesity indices of the arterial hypertension prevalence rate were adjusted by the ratio of the frequency of arterial hypertension in the most young occupational and reference comparable groups. Identification of HWPW was executed by comparing the frequency of AH among workers retiring within 3 years from the occupational groups when compared to the whole sample. Then on the additional risk value there was adjusted the overall prevalence rate of AH in the occupation profession to overcome EHWPW. As a result of the consistent correction and elimination of the influence of HWE components on the prevalence rate of AH, there were obtained risks values, primarily reflecting the impact of occupational factors which can be considered as true occupational risks. Factors of the cardiovascular risk and HWE significantly modified true occupational risks for AH in a number of occupational groups up to inversion. At the same time, the pronouncement of EHR has a paramount importance in the modifying effect.

The effect of a tectonic stress field on coal and gas outbursts.

Coal and gas outbursts have always been a serious threat to the safe and efficient mining of coal resources. Ground stress (especially the tectonic stress) has a notable effect on the occurrence and distribution of outbursts in the field practice. A numerical model considering the effect of coal gas was established to analyze the outburst danger from the perspective of stress conditions. To evaluate the outburst tendency, the potential energy of yielded coal mass accumulated during an outburst initiation was studied. The results showed that the gas pressure and the strength reduction from the adsorbed gas aggravated the coal mass failure and the ground stress altered by tectonics would affect the plastic zone distribution. To demonstrate the outburst tendency, the ratio of potential energy for the outburst initiation and the energy consumption was used. Increase of coal gas and tectonic stress could enhance the potential energy accumulation ratio, meaning larger outburst tendency. The component of potential energy for outburst initiation indicated that the proportion of elastic energy was increased due to tectonic stress. The elastic energy increase is deduced as the cause for a greater outburst danger in a tectonic area from the perspective of stress conditions.

ENVIRONMENTAL IMPACT ON PHYSIOLOGICAL RESPONSES OF UNDERGROUND COAL MINERS IN THE EASTERN PART OF INDIA.

Coal in India is extracted generally by semi-mechanized and mechanized underground mining methods. The Bord and Pillar (B & P) mining method still continues to be popular where deployment of manual miners is more than that of other mining methods. The study is conducted at haulage based mine of Eastern Coalfields of West Bengal. Underground miners confront with a lot of hazards like extreme hostile environment, awkward working posture, dust, noise as well as low luminosity. It is difficult to delay the onset of fatigue. In order to study the physiological responses of trammers, various parameters like working heart rates, net cardiac cost and relative cardiac cost including recovery heart rate patterns are recorded during their work at site. Workload classification of trammers has been done following various scales of heaviness. The effect of environment on the physiological responses has been observed and suitable recommendations are made. The work tasks are bound to induce musculoskeletal problems and those problems could be better managed through rationalizing the work-rest scheduling.

"Nuisance dust": unprotective limits for exposure to coal mine dust in the United States, 1934-1969.

I examine the dismissal of coal mine dust as a mere nuisance, not a potentially serious threat to extractive workers who inhaled it. In the 1930s, the US Public Health Service played a major role in conceptualizing coal mine dust as virtually harmless. Dissent from this position by some federal officials failed to dislodge either that view or the recommendation of minimal limitations on workplace exposure that flowed from it. Privatization of regulatory authority after 1940 ensured that miners would lack protection against respiratory disease. The reform effort that overturned the established misunderstanding in the late 1960s critically depended upon both the production of scientific findings and the emergence of a subaltern movement in the coalfields. This episode illuminates the steep challenges often facing advocates of stronger workplace health standards.

Coal mining, social injustice and health: a universal conflict of power and priorities.

Given the current insatiable demand for coal to build and fuel the world's burgeoning cities the debate about mining-related social, environmental and health injustices remains eminently salient. Furthermore, the core issues appear universally consistent. This paper combines the theoretical base for defining these injustices with reports in the international health literature about the impact of coal mining on local communities. It explores and analyses mechanisms of coal mining related injustice, conflicting priorities and power asymmetries between political and industry interests versus inhabitants of mining communities, and asks what would be required for considerations of health to take precedence over wealth.

Specifications for medical examinations of underground coal miners. Final rule.

This final rule modifies the Department of Health and Human Services (HHS) regulations for medical examinations of underground coal miners. Existing regulations established specifications for providing, interpreting, classifying, and submitting film-based roentgenograms (now commonly called chest radiographs or X-rays) of underground coal miners. The revised standards modify the requirements to permit the use of film-based radiography systems and add a parallel set of standards permitting the use of digital radiography systems. An additional amendment requires coal mine operators to provide the National Institute for Occupational Safety and Health (NIOSH) with employee rosters to assist the Coal Workers' Health Surveillance Program in improving participation by miners.

Approval tests and standards for closed-circuit escape respirators. Final rule.

This final rule announces updated requirements that the National Institute for Occupational Safety and Health (NIOSH or Agency), located within the Centers for Disease Control and Prevention (CDC) in the Department of Health and Human Services (HHS or Department), will employ to test and approve closed-circuit respirators used for escaping atmospheres considered to be immediately dangerous to life and health, including such respirators required by the Mine Safety and Health Administration (MSHA) for use in underground coal mines. NIOSH and MSHA jointly review and approve this type of respirator used for mine emergencies under regulations concerning approval of respiratory protective devices. NIOSH also approves these respirators for use in other work environments where escape equipment may be provided to workers, such as on vessels operated by U.S. Navy and Coast Guard personnel. The purpose of these updated requirements is to enable NIOSH and MSHA to more effectively ensure the performance, reliability, and safety of CCERs.