Underground Mining Safety (Part 1)

As I was preparing this article, I thought to myself, I don’t know of any another jobs more dangerous than mining, tunneling, or any other type of underground construction. There are so many people you have to depend on, not only for your job, but your life as well. People above ground monitoring air and gases, generators, maintaining equipment, just to name a few. Everyone above and below ground has to work together to insure production and safety. I hope that the following information is helpful and you can use it as you go about your day. I’ve included safety guidelines for all aspects of underground work. If I can be of any further help. Don’t hesitate to ask.

The construction of underground tunnels, shafts, chambers, and passageways are essential yet dangerous activities. Working under reduced light conditions, difficult or limited access and egress, with the potential exposure to air contaminants and the hazards of fire and explosion, underground construction workers face many dangers.

These hazards include reduced natural ventilation and light, difficult and limited access and egress, exposure to air contaminants, fire, flooding, and explosion. Tunnels are generally grouped in four broad categories, depending on the material through which they pass: soft ground, consisting of soil and very weak rock; hard rock; soft rock, such as shale, chalk, and friable sandstone; and subaqueous. While these four broad types of ground condition require very different methods of excavation and ground support, nearly all tunneling operations nevertheless involve certain basic procedures: investigation, excavation and materials transport, ground support, and environmental control. Similarly, tunnels for mining and for civil-engineering projects share the basic procedures but differ greatly in the design approach toward permanence, owing to their differing purposes. Many mining tunnels have been planned only for minimum-cost temporary use during ore extraction, although the growing desire of surface owners for legal protection against subsequent tunnel collapse may cause this to change. By contrast, most civil engineering or public-works tunnels involve continued human occupancy plus full protection of adjacent owners and are much more conservatively designed for permanent safety. In all tunnels, geologic conditions play the dominant role in governing the acceptability of construction methods and the practicality of different designs. Indeed, tunneling history is filled with instances in which a sudden encounter with unanticipated conditions caused long stoppages for changes in construction methods, in design, or in both, with resulting great increases in cost and time.

We all know the dangerous conditions in which miner’s work, over the years we have been made aware of the realities of those dangers. The devastating cave-ins, the injuries and loss of life. There are so many different causes, from worker error to nature itself. I want to list some of the accidents that have occurred over the past 10 to 15 years. They have helped to increase safety awareness and guidelines throughout the world. There will always be dangers. It’s the life of working underground. But strictly following federal, state and company guidelines will greatly reduce injury, cave-ins, and the loss of life. 

-At the Awali Tunnel in Lebanon, for example, a huge flow of water and sand filled over 2 miles of the bore and more than doubled construction time to eight years for its 10-mile length.

-Heilongjiang (Heilungkiang) province, China. A powerful gas explosion at the Xiji (Hsi-chi) coal mine claimed the lives of 47 miners and left 32 missing and presumed dead.
 
-West Bengal, India. Lethal carbon monoxide emissions from a fire that was caused by a short circuit killed 55 miners at a coal mine near Asansol.

-Queensland, Australia. A series of gas explosions trapped 11 miners underground; all succumbed to the toxic fumes.

- Mindanao Island, Philippines. A powerful gas explosion ripped through the country's largest coal mine near Malangas; 90 of the 170 miners working underground were killed.

-Slov'yanoserbsk, Ukraine. An explosion in a coal mine claimed the lives of 24 miners and injured 15; methane gas was suspected as a cause of the blast.

-Yunnan province, China. A gas explosion in a poorly ventilated mine killed 32 workers and injured 12; the mine, which had operated in violation of safety regulations, was closed by the government.

-Sorgun, Turkey. An explosion trapped at least 40 miners and injured 5.
 
-Near Vorkuta, Russia. Two separate gas explosions that occurred in the same mine on successive days resulted in the deaths of a total of 15 persons.

-Near Johannesburg, South Africa. A runaway underground locomotive at the Vaal Reefs gold mine plowed through a safety mechanism, plunged down a mine shaft, and crushed more than 100 miners who were descending in a cage; all were killed.

-Mieres, Spain. A gas explosion in a deep coal mine killed 14 miners.

-Kemerovo, Russia. A planned explosion in a coal mine, where 81 miners were working, claimed the lives of 15 miners who were killed when the cage in which they were riding collapsed as a result of the blast.

The need for a “competent person”
The definition of a “competent person” is as follows: One who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them. Underground Construction, caissons, cofferdams, and compressed air, a competent person is responsible for inspecting and evaluating workplace conditions, including air monitoring and the presence of air contaminants, ground stability, and the drilling, hauling and hoisting of equipment, to identify and correct any deficiencies.

Training requirements
All employees involved in underground construction must be trained to recognize and respond to hazards associated with this type of work. Training should be tailored to the specific requirements of the jobsite and include any unique issues or requirements. The following topics should be part of an underground construction employee training program:
? Air monitoring and ventilation
? Illumination
? Communications
? Flood control
? Personal protective equipment
? Emergency procedures, including evacuation plans
? Check-in/check-out procedures
? Explosives
? Fire prevention and protection
? Mechanical equipment

Notification and communication requirements
Any time an employer receives a notification of a hazardous condition, all oncoming shifts must be notified of occurrences or conditions that either have affected or might affect their safety.
Examples of this type of situation include equipment failures, earth or rockslides, cave-ins, flooding, fires, explosions, or release of gas. The employer must also maintain open lines of communication with other employers at the worksite to ensure a rapid and complete exchange of information concerning events or situations that may impact worker safety.

Employers must maintain lines of communication with employees during underground construction activities. To ensure effective communications are always available, communication systems must be tested upon initial entry of each shift to the underground and as often as necessary at a later time to ensure they are in working order. Powered communication systems must operate on an independent power supply and be installed so that the use of or disruption of any single communication device or signal location will not disrupt the operation of the system in any other location. If natural unassisted voice communication is ineffective at any time, a power-assisted means must be used to ensure communication between the work face, the bottom of the shaft, and the surface. In the case of an individual employee working alone underground in a hazardous location who is out of range of natural unassisted voice communication and not able to be observed by other employees, the employer must provide an effective means of obtaining assistance in the event of an emergency. All shafts being developed or used for personnel access or hoisting require two effective means of communication. In addition, hoist operators must have a closed-circuit voice communication system connected to each landing station, with speaker microphones located so that the operator can communicate with individual stations while the hoist is in use.

Site control procedures

Check-in/check-out procedures
The employer must maintain a check-in/check-out procedure to ensure that above ground personnel maintain an accurate accounting of the number of persons underground and to prevent unauthorized persons from gaining access to the site. This is especially important in the event of an emergency but is a common sense requirement at all times.
The only time this procedure is not required is when an underground construction project designed for human occupancy is completed to the point that permanent environmental controls are effective and any remaining construction activity does not have the potential to create an environmental hazard or structural failure in the construction area.
Any time an employee is working underground, at least one designated person must be on duty above ground. This person is responsible for calling for immediate assistance and keeping an accurate count of employees who remain underground in the event of an emergency.

Control of access and egress
In addition to establishing a check-in/check-out procedure, the employer must ensure safe access to and egress from all workstations at the construction site to protect employees from potential hazards, such as being struck by excavators, haulage machines, or other moving equipment. To help control access, all unused openings, including chutes and man ways, must be tightly covered; bulk headed, barricaded, or fenced off, and posted with warning signs that read, “Keep Out” or similar language.

Ground support of portal and subsidence areas
Portal openings and access areas must be guarded by shoring, fencing, head walls, shotcreting or equivalent protection to ensure that employees and equipment have a safe means to access these areas. Subsidence areas must be similarly guarded by shoring, filling in, or placing barricades and warning signs to prevent entry. Adjacent areas must be scaled or secured to prevent loose soil, rock, or fractured materials from endangering portal, subsidence, and access areas.

Ground support of underground areas
A competent person must inspect the roof, face, and walls of the work areas at the beginning of each shift and as often as necessary to ensure ground stability. The competent person tasked with such inspection responsibilities must be protected from loose ground by location, ground support, or equivalent means. The ground conditions along all haulage ways and travel ways must also be inspected as frequently as necessary to ensure safe passage and loose ground considered to be hazardous to employees must be scaled, supported, or taken down.
A competent person must determine how often rock bolts need to be tested to ensure that they meet the necessary torque, taking into consideration ground conditions, distance from vibration sources, and the specific bolt system in use. Only torque wrenches should be used when torsion-dependent bolts are used for ground support.
Employees involved in installing ground support systems must be adequately protected from the hazards of loose ground. The bottoms of any support sets installed must have sufficient anchorage to prevent ground pressures from dislodging the support base. Lateral bracing (including collar bracing, tie rods, or spreaders) must be provided between immediately adjacent sets to increase stability.
Any dislodged or damaged ground supports that create a hazardous condition must be promptly repaired or replaced. The new supports must be installed before removing the damaged supports. Some type of support, such as a shield, must be used to maintain a safe travel way for employees working in dead-end areas ahead of any support replacement operations.

Ground support of shafts
Shafts and wells more than 5 feet in depth (1.53 m) entered by employees must be supported by steel casing, concrete pipe, timber, solid rock, or other suitable material. The full depth of the shaft must be supported except where it penetrates into solid rock that will not change as a result of exposure. Where the potential for shear exists, where the shaft passes through earth into solid rock in either direction, or where the shaft ends in solid rock, the casing or bracing must extend at least 5 feet (1.53 m) into the solid rock. The casing or bracing must also extend 42 (± 3) inches above ground level unless a standard railing is installed, the adjacent ground slopes away from the shaft collar, and barriers exist to prevent mobile equipment operating near the shaft from jumping over the bracing. If these conditions are met, the casing or bracing may be reduced to 12 inches above ground.

Fire prevention and control
In addition to the basic fire prevention and control underground construction operations are subject to several specific requirements. Open flames and fires are prohibited in underground construction areas except as permitted for welding, cutting, or other hot work operations. Smoking is prohibited unless an area is free of fire and explosion hazards. Signage prohibiting smoking and open flames should be placed throughout work areas. Fire extinguishers of at least 4A:40B:C rating or equivalent extinguishing means must be available at the head and tail pulleys of underground belt conveyers.

All underground structures and those within 100 feet (30.48 m) of an opening to the underground must be constructed of materials with a fire resistance rating of at least one hour. Also, no flammable or combustible material may be stored above ground within 100 feet (30.48 m) of any access point to an underground operation. If space limitations make this unfeasible, the material must be positioned as far as possible from the entrance with a fire resistant barrier that has at least a one-hour rating between the material and the opening. Alternative precautionary measures may be adopted from industry practices used under similar working conditions or measures recommended under industry consensus standards. A site hazard analysis may be helpful to determine the effectiveness of precautionary measures. Any spill of flammable or combustible material must be cleaned up immediately. Gasoline may not be underground at any time for any purpose due to its volatile qualities. Internal combustion engines (except diesel-powered engines on mobile equipment) are prohibited underground. Acetylene, liquefied petroleum gas, and methyl acetylene propadiene stabilized gas may be used underground for welding, cutting, and other hot work. if all requirements of regulations pertaining to such activities are met. Only enough fuel gas and oxygen cylinders for welding, cutting, or hot work during a 24-hour period are allowed underground. Noncombustible barriers must be installed below such activities if they are performed in or over a shaft or rise. Oil, grease, and diesel fuel stored underground must be kept in tightly sealed containers in fire-resistant areas at least 300 feet (91.44 m) from underground explosive magazines, and at least 100 feet (30.48 m) from shaft stations and steeply inclined passageways. Storage areas must be positioned or diked to ensure that if a container breaks open, any fluids will not flow out of the storage area. Any hydraulically-actuated underground machinery must use fire-resistant hydraulic fluids unless it is protected by a fire suppression system or multi-purpose fire extinguisher rated at least 4A:40B:C and of sufficient capacity for the type and size of equipment involved. Several specific requirements apply to the use of diesel fuel in underground construction operations, as follows:

? A surface level tank holding diesel fuel to be pumped to an underground storage site must have a maximum capacity no greater than the amount of fuel required to supply underground equipment for 24 hours.
? A surface level tank must be connected to the underground fueling station by an acceptable pipe or hose system controlled at the surface by a valve and at the bottom by a hose nozzle.
? The transfer pipe must remain empty at all times except when transferring diesel fuel.
? All hoisting operations in the shaft must be suspended during refueling operations if the supply piping in the shaft is not protected from potential damage.

Ventilation requirements
Fresh air must be supplied to all underground work areas in sufficient amounts to prevent any dangerous or harmful accumulation of dusts, fumes, mists, vapors, or gases. If natural ventilation does not provide the necessary air quality through sufficient air volume and air flow, the employer must provide mechanical ventilation to ensure that each employee working underground has at least 200 cubic feet (5.7m3) of fresh air per minute. When performing work that is likely to produce dust, fumes, mists, vapors, or gases (such as blasting or rock drilling), the linear velocity of air flow in the tunnel bore, shafts, and all other underground work areas must be at least 30 feet (9.15 m) per minute. When such operations are complete, the ventilation systems must exhaust smoke and fumes to the outside atmosphere before resuming work in all affected areas. When drilling rock or concrete, dust control measures such as wet drilling, vacuum collectors, and water mix spray systems must be used to maintain dust levels within limits set by the industry, which includes gases, vapors, fumes, dusts, and mists. The direction of mechanical airflow must be reversible but ventilation doors must be designed and installed to remain closed when in use, regardless of the direction of the airflow. If the ventilation system has been shut down and all employees are removed from the underground area, only competent persons authorized to test for air contaminants may be allowed underground until the ventilation system has been restored and all affected areas have tested at acceptable limits for air contaminants.

Illumination requirements
As in all construction operations, it is required that proper illumination be provided during tunneling operations. When explosives are handled, only acceptable portable lighting equipment may be used within 50 feet of any underground heading. For general tunneling operations, a minimum illumination intensity of 5 foot-candles must be maintained, although 10 foot-candles must be provided for shaft heading during drilling, mucking, and scaling

Please read Part2 by clicking here...

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