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.

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.

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 PM_2.5 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 PM_2.5, 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 PM_2.5 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.

[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.

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.

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.

Citation-related reliability analysis for a pilot sample of underground coal mines

The scrutiny of underground coal mine safety was heightened because of the disasters that occurred in 2006-2007, and more recently in 2010. In the aftermath of the 2006 incidents, the U.S. Congress passed the Mine Improvement and New Emergency Response Act of 2006 (MINER Act), which strengthened the existing regulations and mandated new laws to address various issues related to emergency preparedness and response, escape from an emergency situation, and protection of miners. The National Mining Association-sponsored Mine Safety Technology and Training Commission study highlighted the role of risk management in identifying and controlling major hazards, which are elements that could come together and cause a mine disaster. In 2007 MSHA revised its approach to the "Pattern of Violations" (POV) process in order to target unsafe mines and then force them to remediate conditions in their mines. The POV approach has certain limitations that make it difficult for it to be enforced. One very understandable way to focus on removing threats from major-hazard conditions is to use citation-related reliability analysis. The citation reliability approach, which focuses on the probability of not getting a citation on a given inspector day, is considered an analogue to the maintenance reliability approach, which many mine operators understand and use. In this study, the citation reliability approach was applied to a stratified random sample of 31 underground coal mines to examine its potential for broader application. The results clearly show the best-performing and worst-performing mines for compliance with mine safety standards, and they highlight differences among different mine sizes.

Submicrometer elemental carbon as a selective measure of diesel particulate matter in coal mines

A monitoring method for diesel particulate matter was published as Method 5040 by the National Institute for Occupational Safety and Health (NIOSH). Organic and elemental carbon are determined by the method, but elemental carbon (EC) is a better exposure measure. The US Mine Safety and Health Administration (MSHA) proposed use of NIOSH 5040 for compliance determinations in metal and nonmetal mines. MSHA also published a rulemaking for coal mines, but no exposure standard was provided. A standard based on particulate carbon is not considered practical because of coal dust interference. Interference may not be a problem if an appropriate size-selective sampler and EC exposure standard are employed. Submicrometer dust concentrations found in previous surveys of nondieselized, underground coal mines were relatively low. If a large fraction of the submicrometer dust is organic and mineral matter, submicrometer EC concentrations would be much lower than submicrometer mass concentrations. Laboratory and field results reported herein indicate the amount of EC contributed by submicrometer coal dust is minor. In a laboratory test, a submicrometer EC concentration of 31 microg m(-3) was found when sampling a respirable coal dust concentration over three times the US compliance limit (2 mg m(-3)). Laboratory results are consistent with surveys of nondieselized coal mines, where EC results ranged from below the method limit of detection to 18 microg m(-3) when size-selective samplers were used to collect dust fractions having particle diameters below 1.5 microm-submicrometer EC concentrations were approximate 7 microg m(-3). In dieselized mines, submicrometer EC concentrations are much higher.

[Characteristics of autonomic regulations in miners working in hard conditions of coal mines]

72 miners aged from 30 till 40 years have been surveyed. It was established that to achieve socially acceptable results the miners use corresponding strategy doing their job. Under the influence of the work the functional states mediated not only by conditions of working environment but also by resistivity of the organism are developed. It is shown that highly productive, reliable and effective work is possible under adequate interactions of central and autonomic mechanisms of regulation. Alteration in these interactions, particularly, non-adequate centralization of management processes decreases physical capacity for work. Enhancement of sympathetic effects on periphery that leads to development of hypertensive reactions has been observed. Such alterations are accompanied by an increase in physiological cost of work and decreased productivity of labor.

Respiratory symptoms and spirometry in experienced coal miners: effects of both distant and recent coal mine dust exposures

The goal of this study was to determine whether respiratory symptoms were associated with the lower concentrations of respirable coal mine dust that were required by the U.S. Coal Mine Health and Safety Act (CMHSA) of 1969. The subjects were 1,866 male miners who had participated in the National Study of Coal Workers' Pneumoconiosis (NSCWP) and been tested at least twice, initially in either Round 1 (R1) (1969-71) or Round 2 (R2) (1972-75) and then finally in Round 4 (R4) (1985-88). Self-reported information elicited with a standardized questionnaire was used to determine the presence at the final round (i.e., R4) of chronic bronchitis, shortness of breath, and wheeze. Cumulative coal mine dust exposure was characterized for both the pre- and post-CMHSA periods. Controlling for age and other potential confounders, increased risks for the symptoms were associated with higher levels of both measurements of exposure. Moreover, the adverse effects of the lower, post-CMHSA exposure were evident for shortness of breath and wheeze especially among subjects who had little pre-CMHSA coal mining experience. These findings provide additional evidence of the limitations of the current 2.0 mg/m3 coal mine dust standard to prevent respiratory disease.

[Characteristics of lipid metabolism in deep mine workers and the ways of its alimentary correction]

Lipid and antioxidant state of clinically normal subjects working in deep mines was studied under natural conditions during one month. Disorders in lipid metabolism and intensified peroxidation were recorded in these subjects. A prophylactic ration has been recommended considering the food status, alimentary risk factors and extreme conditions of miners' labour.

[Use of the pulsimetric method for estimating energy value of food rations for miners in deep coal mines]

Pulsimetry proved to be the most acceptable method for estimating energy requirements of miners working under extreme conditions with constantly changing ergometric parameters. It has been established that the mean daily energy requirements of miners working in deep coal mines under conditions of high temperature comprise 3500 kcal. Energy requirements for the main types of the physical activity of workers in deep mines have been calculated, basing on basal metabolism, metabolic constants for varying activities have been determined.

[The role of ecological factors and working conditions in the development of occupational pathology in the Donetsk region]

Among the factors producing effects on the formation of indexes of morbidity of the people working in Donbass, the main role is played by the ecological situation in the region, working conditions and lifestyle of the working people. On the basis of morbidity indexes analysis proposals and measures aimed at the preservation and improvement of health of the working people are formulated.

[Hygienic substantiation of the information and energy models of variable noise]

The results of the technological studies and chamber experiment provided the basis for the conception according to which noise information parameters contributed to its biologic activity identically with energetic characteristics. The calculation results obtained by the regression model showed that noise MAC with account of its information value should be at least 5-10 dBA less than the existing ones. Information parameters should also be regulated.

[Effect of working conditions in deep coal mines of the Donetsk region on the course of ischemic heart disease in miners]

Clinical and functional examination of the miners who suffered from coronary heart disease showed a higher ectopic activity of the myocardium during their work under underground conditions and during the subsequent 4 hours after its termination. It also indicated a significantly higher fatal cases of sudden coronary death in the miners in the aforementioned periods. To prevent the development of complications occurred in miners, the status of the cardiovascular system was proposed to be dynamically controlled.

The effect of public controversy on occupational health problems: byssinosis

The effect of the byssinosis controversy on surveillance programs in the cotton textile industry is reviewed. The federally regulated format for industry medical surveillance guarantees neither automatic reduction of cotton dust exposure for high-risk workers nor wage rate retention for workers who are transferred to less dusty job sites. The absence of universal guidelines for worker management, combined with doubt over the severity and prevalence of byssinosis, encourages employers to evaluate medical surveillance programs primarily on the basis of their economic impact. When employers use the programs to control their losses, the potential costs of worker participation are increased. Comparisons with medical surveillance programs in the coal industry suggest that health benefits to workers can be guaranteed in the context of disputes over occupational diseases if industry, labor, and government agencies all participate in program design and operation.

Symbolic solutions for deadly dilemmas: an analysis of federal coal mine health and safety legislation

Numerous studies of coal mine laws have argued that the passage of all significant health and safety legislation can be attributed to a succession of catastrophic disasters which heightened awareness and propelled lawmakers into action. This paper takes issue with this "disaster-law" argument because it obscures the intricacies of law creation by focusing on a single factor. More accurately, mining disasters represent one dimension of a process aimed at resolving conflicts occurring within a specific social context. Historically, legislation has been utilized to avert economic crises by addressing the demands of protesting miners. Unfortunately, while the "written law" assured improvements, the "law in action" did not meet these guarantees and the deaths in the mines continued. A case study of the Coal Mine Health and Safety Act of 1969 demonstrates how a law with apparently progressive standards can fail to effect change because of its dualistic nature and incomplete implementation.

Fatality rates and regulatory policies in bituminous coal mining, United States, 1959-1981

In the eleven years prior to the passage of the Federal Coal Mine Health and Safety Act of 1969, fatality rates changed little for underground miners and were increasing for surface miners. Following implementation of the 1969 Act, both rates decreased. Beginning in 1979, and continuing into the first six months of 1982, both rates increased. These associations suggest that current relaxation of regulations and policies for coal mine safety are unwarranted.

The worker as teacher

The worker is the major source of information about job hazards. Frequently, workers themselves discover new occupational diseases. Physicians need to regard the worker as a member of the occupational health team.