Roof Bolting Research Articles

The Evaluation and Quantification of Respirable Coal and Silica Dust Concentrations: A Task-based Approach

Silicosis and coal worker's pneumoconiosis are serious occupational respiratory diseases associated with the coal mining industry and the inhalation of respirable dusts containing crystalline silica. The purpose of this study (funded by the Mine Health and Safety Council of South Africa) was to evaluate the individual contributions of underground coal mining tasks to the respirable dust and respirable silica dust concentrations in an underground section by sampling the respirable dust concentrations at the intake and return of each task. The identified tasks were continuous miner (CM) cutting, construction, transfer of coal, tipping, and roof bolting. The respirable dust-generating hierarchy of the tasks from highest to lowest was: transfer of coal > CM right cutting > CM left cutting > CM face cutting > construction > roof bolting > tipping; and for respirable silica dust: CM left cutting > construction > transfer of coal > CM right cutting. Personal exposure levels were determined by sampling the exposures of workers performing tasks in the section. Respirable dust concentrations and low concentrations of respirable silica dust were found at the intake air side of the section, indicating that air entering the section is already contaminated. The hierarchy for personal respirable dust exposures was as follows, from highest to lowest: CM operator > cable handler > miner > roof bolt operator > shuttle car operator, and for respirable silica dust: shuttle car operator > CM operator > cable handler > roof bolt operator > miner. Dust control methods to lower exposures should include revision of the position of workers with regard to the task performed, positioning of the tasks with regard to the CM cutting, and proper use of the line curtains to direct ventilation appropriately. The correct use of respiratory protection should also be encouraged.

Deformational criteria for the stability of roof rocks and rock bolts

The authors discuss issues of stage-wise rock bolting of mine workings. Using equivalent material models, permissible roof rock lamination for roof bolting in conformity with the excavation support standards is evaluated. The critical displacements of roof rocks that make stage-wise roof bolting impossible are calculated.

Chracterizition of Dynamic Properties of Roof Bolts and their Applications

The dynamic properties of rock bolts are characterized by measurement. The acceleration and strain of a rock bolt specimen were recorded using axial impact testing in laboratory environment. The systems dynamic properties such as natural frequencies and damping are characterized by using spectral analysis and Wavelet method. The characterized dynamic properties are used to update and calibrate a system simulation model, which is a multiple-degree-of-freedom system involving roof mass, the roof bolt, grout interface and head connections. The proposed approach enables accurately and effectively quantifying system dynamic parameters and establishing the analytical model for the design, development and performance monitoring of roof bolting systems.

THE RESULTS OF AT ROOFBOLTING SYSTEM OF SUPPORT APPLICATION IN ''SOKO'' UNDERGROUND MINE

<p>Complex mining and geological conditions of coal exploitation, such as the Soko mine, requiring the<br>constant work on the research of new technical solutions of development and supporting of the<br>underground openings.<br>In this paper presented detailed description of the existing way of development and support<br>underground openings at the mine Soko.<br>Experience in the current method of development and supporting of the openings showed a number of<br>disadvantages especially in terms of increased underground pressures that have affected the<br>deformation of underground openings.<br>Installing AT roof bolting system of support and test support in the drift EH- (-60) z in the underground<br>mine Soko with the combined support represent the new solutions of development and support and<br>function of the increasing stability of mining facilities, extending the life of their exploitation and<br>functionality. </p>

A Critical Study on the Underground Environment of Coal Mines in India-an Ergonomic Approach

Ergonomics application on underground miner’s health plays a great role in controlling the efficiency of miners. The job stress in underground mine is still physically demanding and continuous stress due to certain posture or movement of miners during work leads to localized muscle fatigue creating musculo-skeletal disorders. A good working environment can change the degree of job heaviness and thermal stress (WBGT values) can directly have the effect on stretch of work of miners. Out of many unit operations in underground mine, roof bolting keeps an important contribution with regard to safety of the mine and miners. Occupational stress of roof bolters from ergonomic consideration has been discussed in the paper.

Visual feedback system to reduce errors while operating roof bolting machines

ProblemOperators of roof bolting machines in underground coal mines do so in confined spaces and in very close proximity to the moving equipment. Errors in the operation of these machines can have serious consequences, and the design of the equipment interface has a critical role in reducing the probability of such errors. MethodsAn experiment was conducted to explore coding and directional compatibility on actual roof bolting equipment and to determine the feasibility of a visual feedback system to alert operators of critical movements and to also alert other workers in close proximity to the equipment to the pending movement of the machine. The quantitative results of the study confirmed the potential for both selection errors and direction errors to be made, particularly during training. ResultsSubjective data confirmed a potential benefit of providing visual feedback of the intended operations and movements of the equipment. ImpactThis research may influence the design of these and other similar control systems to provide evidence for the use of warning systems to improve operator situational awareness.

Development of roof bolting use in Polish coal mines

In the paper, after short historical outline, a development of roof bolting use in Polish coal mines on the span of last twenty years was presented. Two characteristic examples of use were given. First of them is related to the solution, which found the widest use in mines. It consists in replacement of abutment at longwall and entry crossing with bolts. Second example concerns the use of independent roof bolting. For both examples, the geological conditions were described, as well as the applied patterns of bolting and the principles of support and mine working stability control.

Severe Occupational Pneumoconiosis Among West Virginian Coal Miners: One Hundred Thirty-eight Cases of Progressive Massive Fibrosis Compensated Between 2000 and 2009

Miners inhale dust at work and are at a risk for coal workers pneumoconiosis (CWP), a preventable and potentially fatal lung disease. After regulations were implemented in the 1970s, declines were reported in both dust levels and the prevalence of simple and advanced CWP until about 2001, when despite stable reported dust levels, disease levels sharply increased. A structured, retrospective chart review was performed to describe the demographics and disease progression for 138 coal miners with progressive massive fibrosis (PMF) whose claims were approved by the West Virginia State Occupational Pneumoconiosis Board between January 2000 and December 2009. PMF, a complication of CWP, developed in 138 West Virginian coal miners at a mean age of 52.6 years after an average of 30 years work tenure. The time of progression averaged 12.2 years from the last normal chest radiograph until PMF was detected. Lung function declined sharply in both smokers and nonsmokers, averaging 87 mL/y for FEV(1) and 74 mL/y for FVC. The board has confirmed 21 deaths in this group. The most common job activities were operating continuous-mining machines (41%) and roof bolting (19%). Virtually all of these miners' dust exposures occurred after the implementation of current federal dust regulations. Contemporary occupational dust exposures have resulted over the past decade in rapidly progressive pneumoconiosis and massive fibrosis in relatively young West Virginian coal miners, leading to important lung dysfunction and premature death.

Validation of RMR-based support design using roof bolts by numerical modeling for underground coal mine of Monnet Ispat, Raigarh, India—a case study

In underground coal mines, a lot of major fatalities have occurred due to roof fall in the newly developed faces or galleries of coal mines during the development or production of coal. There are around 500 underground coalmines in India, and continuous production or development or exploitation of coal depends upon the stability of the gateways developed in the form of galleries, which are supported in such a manner so that they can last up to that period, unless it has been finally extracted out with an operation called depillaring. A system of support design with roof bolting, resin bolting, and cable bolting for the aforesaid galleries is presently being decided on the basis of rock mass rating (RMR). The same support design has been attempted with the use of 3D numerical modeling technique—a tool nowadays very extensively used in geotechnical engineering to predict the stability of structures to be built or for the structures which are built against nature, i.e., underground mines. In this study, the support design system on the basis of RMR has also been validated with a numerical modeling technique for three locations of Monnet Ispat underground coalmine. After the study, it has been found that the numerical modeling technique can give better design of support system in underground coal mines in comparison with RMR-based support design system, and it will also play a major role in reducing the total cost incurred in coal exploitation from the underground coal mines.

Development of elastomeric isolators to reduce roof bolting machine drilling noise.

Among underground coal miners, hearing loss remains one of the most common occupational illnesses. In response to this problem, the National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) conducts research to reduce the noise emission of underground coal-mining equipment, an example of which is a roof bolting machine. Field studies show that, on average, drilling noise is the most significant contributor to a roof bolting machine operator's noise exposure. NIOSH OMSHR has determined that the drill steel and chuck are the dominant sources of drilling noise. NIOSH OMSHR, Corry Rubber Corporation, and Kennametal, Inc. have developed a bit isolator that breaks the steel-to-steel link between the drill bit and drill steel and a chuck isolator that breaks the mechanical connection between the drill steel and the chuck, thus reducing the noise radiated by the drill steel and chuck, and the noise exposure of the roof bolter operator. This paper documents the evolution of the bit isolator and chuck isolator including various alternative designs which may enhance performance. Laboratory testing confirms that production bit and chuck isolators reduce the A-weighted sound level generated during drilling by 3.7 to 6.6 dB. Finally, this paper summarizes results of a finite element analysis used to explore the key parameters of the drill bit isolator and chuck isolator to understand the impact these parameters have on noise.

The development of a damped drill steel to reduce roof bolting machine drilling noise.

Among underground coal miners, hearing loss remains one of the most common occupational illnesses. In response, the National Institute for Occupational Safety and Health (NIOSH) conducts research to reduce the noise emission of various underground coal mining equipment, an example of which is a roof bolting machine. Field studies support the premise that, on average, drilling noise is the loudest noise that a roof bolting machine operator would be exposed to and contributes significantly to the operators’ noise exposure. NIOSH has determined that the drill steel radiates a significant amount of noise during drilling. NIOSH has conducted research to evaluate a damped drill steel to reduce noise radiation. With this reduction in drilling noise, the noise exposure of the roof bolting machine operator is reduced. This paper documents the research to date of this damped drill steel. Laboratory testing confirms that the concept of a damped drilll steel reduces sound levels generated during drilling, and by extension, operator noise dose exposure.

A control suite to reduce roof bolting machine drilling noise.

Among underground coal miners, hearing loss remains one of the most common occupational illnesses. In response, the National Institute for Occupational Safety and Health (NIOSH) conducts research to reduce the noise emission of various underground coal mining equipment, an example of which is a roof bolting machine. Field studies support the premise that, on average, drilling noise is the loudest noise that a roof bolting machine operator would be exposed to and contributes significantly to the operators’ noise exposure. NIOSH has determined that the drill steel radiates a significant amount of noise during drilling. NIOSH in collaboration with Corry Rubber Corporation has developed a suite of controls to reduce drilling noise which consists of a bit isolator, chuck isolator, and a Collabsible Drill Steel Enclosure. This control suite effectively reduces the noise radiated by the drill steel. Laboratory testing confirms that the control suite reduces sound pressure levels generated during drilling by 13 dB(A) at the operator’s location. As a result of this reduction in drilling noise, the noise exposure of the roof bolting machine operator is reduced.

Noise and vibration assessment of a roof bolting machine

In its 1996 National Occupational Research Agenda, the National Institute of Occupational Safety and Health (NIOSH) identified hearing loss as the most common job-related disease in the United States. Previous field studies by NIOSH have shown A-weighted sound levels at the operator's station on roof bolting machines used in coal mines exceed 100 dB when drilling. Laboratory vibration measurements conducted while drilling indicated that drill steel acceleration levels greatly exceed those of the drill motor, drill motor cover, the roof support plate, and the drilled media. Sound level measurements performed with parts of the drilling apparatus and the drilled media wrapped in lead-fiberglass barrier-absorber blankets revealed that the drill steel is the dominant noise source. To evaluate the ability of a partial-height barrier to reduce operator noise exposure, 80% of the drill steel length was encapsulated in a quilted lead-fiberglass barrier-absorber sleeve. The partial-height barrier reduced the time-weighted average sound level (TWA) by 9.8 dB for the Mine Safety and Health Administration (MSHA) Permissible Exposure Level (PEL) criteria and 9.3 dB for the NIOSH Recommended Exposure Limit (REL) criteria

The aesthetics of rock construction work: the beauty of sprayed concrete, rock reinforcement and roof bolting

The concepts of aesthetic and aesthetic knowledge have recently been appropriated and discussed in the organization theory literature. In this broader recognition of human skills and capacities complementing the conventional rational and logical modes of thinking prioritized in scientific thinking, a few studies reports how aesthetic knowledge is employed in areas not regularly associated with aesthetics, for instance computer programming or financial analysis. This paper reports how the concepts of aesthetic and aesthetic knowledge can be used to examine the work of qualified rock construction workers. Rather than being a skill that can be accommodated through training, the best rock construction workers have tacit know‐how that are not easily learned or transferred between co‐workers. Such skills are here referred to as aesthetic knowledge. The paper concludes that more studies of everyday work and aesthetic knowledge may be helpful when rethinking the nature of human and individual knowledge.

Rock mass movements around development workings in various density of standing-and-roof-bolting support

Presented measurement results of roof rocks and wall rock movements of underground development workings after their drifting. The research was carried out in the coal mine workings with standing-and-roof bolting support. There were various density of the support, so the aim of the special monitoring programme was to determine movement intensity of rock mass in the premises of the heading area. There were four types of research did by the authors. They measured convergence, roof layers separation using telltales and sonic probes and load bearing of the headings’ roofs by hydraulic dynamometers. Evaluation of fracture zone around the heading and investigation the load zone caused by failed roof rocks may become a basement for the determination of support parameters of the workings. The combined system of standing support and roof bolting seems to be an essential for underground headings protection.

Drill steel research to reduce roof bolting machine operator noise exposure

NIOSH has devoted significant resources to reducing Noise Induced Hearing Loss (NIHL) among the Nation’s miners. As part of this effort, NIOSH’s Pittsburgh Research Laboratory (PRL) employs a large reverberation chamber for sound power level measurements and a hemi-anechoic chamber and beamforming system for noise source identification. One of several research projects at PRL is investigating noise controls to reduce the noise exposure of roof bolting machine operators. Research findings to date suggest that drill steel vibration is a significant source of the noise emissions generated during the bolting/drilling cycle and a major contributor to the operators’ noise exposure. In this presentation, the laboratory and field test methodologies are explained as well as a summary of the data analysis procedures and testing results. Proper implementation of currently available noise controls can reduce sound levels at the operators’ position from 3 to 7 dB(A) under laboratory conditions. Conclusions drawn from these results and the steps taken to generate effective engineering noise controls for reducing roof bolting machines operators’ noise exposures are also covered.

Computer simulations help determine safe vertical boom speeds for roof bolting in underground coal mines

Problem Incident investigation reports do not usually contain enough information to aid in studying boom arm vertical speed for roof bolting machines to determine the impact that appendage speed had on an operator's risk of experiencing a contact. Laboratory experiments with human subjects are also not feasible because of safety and ethical issues. Method Researchers successfully developed a three-dimensional computer model that uses virtual human simulation software as the primary means to gather contact data when the boom arm touches the operator's hand, arm, head, or leg. Results Data analysis of roof bolter simulations shows that the speed of the boom arm is the most important factor in determining the risk of an operator making contact. Regardless of other variables, contact incidents were always greater when the bolter arm was moving up, greater on the hand, and greater for the boom arm part of the machine. The reason why the subject experiences more contacts when the boom arm is moving up rather than down is that more risky behaviors occur during drilling and bolting when the boom arm is ascending. Based on the data collected, boom speeds greater than 13 in/sec result in a substantial increase in risk to the roof bolter operator of making contact. Speeds less than or equal to 13 in/sec are associated with a more modest relative risk of making contact, which represents a decrease in potential hazard. Impact on Industry The use of such information can be quite helpful in making recommendations to machine design and task procedures to reduce the likelihood that roof bolter operators will experience injury due to contact with a moving roof bolting machine's boom arm.

The influence of seam height on lost-time injury and fatality rates at small underground bituminous coal mines.

Due to variations in the thickness of U.S. coal seams, there is great variability in the height of the roof where underground miners work. Restrictions imposed by low seam heights have important safety consequences. As the height of their workplace decreases, miners must stoop, duck walk, or crawl, and their vision, posture, and mobility become increasingly restricted. Low seam height also places important restrictions on the design of mobile equipment and other mining machinery. Using the employment and injury data reported to the Mine Safety and Health Administration (MSHA) from 1990 to 1996, small underground bituminous coal mines with less than 50 employees were stratified by average coal seam height according to the following categories: low (< or =42"), medium (43"-60"), and high (> or =61"). Injury rates for both nonfatal days lost and fatality cases were examined by seam height and leading type of injury incidents. The leading types of incidents associated with fatalities were roof falls and powered haulage equipment. In comparison to high-seam mines, miners working in low or medium seams are at higher risk of being killed by powered haulage equipment, roof bolting machines, and falls of unsupported roof. The leading types of incidents associated with nonfatal injuries were handling materials and powered haulage. As mining height decreases, miners are at increasingly higher risk of having a nonfatal injury from incidents involving roof bolting machines, load-haul-dump equipment, personnel carriers, and powered haulage conveyors. As mining height increases, miners are at increasingly higher risk of having a nonfatal injury from slips and falls and incidents involving shuttle cars and roof and rib falls. Knee injuries are a particularly severe problem in low-seam mines. The rate of injuries to miners while crawling or kneeling is 10 times higher in low seams than in high seams.

Clinically important FEV1 declines among coal miners: an exploration of previously unrecognised determinants.

OBJECTIVES: The relation between occupational exposure to dust and loss of ventilatory lung function is now well established. However, many exposures during work and other activities might also have important...

Measuring system for monitoring the rock mass stress

The paper presents a computer aided measuring system for monitoring the rock mass stress. The system operates in a frequency modulation mode which ensures interference rejection and enables the transmission of the measurement data over a very long distance. This system consists of three main units: sending, receiving and a cluster unit. In particular, the sending unit, being untypical, is discussed in detail. Finally, by means of example the result of the application of this system in the roof bolting stress monitoring in a hard coal mine is presented.