Blasting related hazards must also be added to that list. Although not specific to underground operations, their consequences may be exacerbated by the confined atmosphere and the workplace configuration.
Accidents are always a combination of hazards and causes. Making the issue more comprehensible is the only reason for presenting the hazards listed below. The collapse and flood of underground workings may be a consequence of a dust or gas explosion. Similarly, a fire can cause dust explosion and/or release toxic contaminants.
Fires and explosions have been some of the most destructive and dangerous hazards in the mining industry. It is also one of the most challenging safety issues that miners face. They can occur at any time, whether that's in an active or abandoned facility.
Some of fires can be so devastating that they can ruin entire towns. The town of Centralia, Pa., was evacuated because of a coal mine fire that began in 1962 and has since been burning. The exact cause of the fire has never been determined.
Just like fires, floods can cause just as much devastation in a mine. There are many reasons why mines can become flooded. Some floods are controlled meaning, they are planned. But in other cases, flooding is unintentional. Some of the reasons why floods occur may be:
The Gleision Colliery mining accident took place on Sept. 15, 2011, when seven miners intentionally detonated an explosive. Following the blast, the mine began filling with water. Three of the miners managed to escape. But rescue workers were not able to save the other four, who were trapped and died underground.
After the inrush at Gleision Colliery, the Health and Safety Executive (HSE) in the United Kingdom issued the HID 4-2011 safety bulletin focusing on Regulations 1979 (Precautions Against Inrushes). This regulation was introduced in 1973 after the Lofthouse Colliery accident, Yorkshire, where seven miners were killed after the mine flooded.
Induced Seismicity: Mines located in seismically active regions, such as the Andean region also known to be one of the wealthiest metallic mining zones in the world are particularly at risk. Especially dangerous in underground mining areas, mine-induced seismicity also causes slope instability in surface mining.
Use of Explosives: The use of explosives may cause earthquake-like events that collapse mine workings, and traps miners, as happened to the 33 miners stuck underground from August to October 2010 in a Chilean mine near the city of Copiapo, or kill them, flood the mine and damage structures on the surface.
Layers of coal trap methane a highly explosive gas. Methane can be released, leading to coal dust explosions when there are mechanical errors from tools that are improperly used or that malfunction. When explosives are also detonated intentionally, they can also lead to coal dust explosions.
One of the world's worst coal mining accidents took place at the Benxihu Colliery in Benxi, China. In April 1962, a fire broke out after gas and coal dust exploded. More than 1,500 miners died in the accident.
Timbering / Pillar Failure: Accidents in mines can be presented by properly securing areas in which miners work with pillars and timbers. These timbers support the roof or a tunnel's face during the excavation or lining process. If these are not properly secured, they may lead to collapse.
You can get an idea about the traditional way to timber a mine by reviewing this video.The role of pillars or timbers is obviously key in underground operations.The instability of pillars induced by stress or other unfavorable causes may lead to horrendous cascading pillar failure mechanisms.
Considering the atmosphere underground is limited and confined, the contaminants may include dust, aerosols, diesel fumes and particulates and fumes from blasting, as well as gasses released from the rock strata.Ventilation is key to extract or dilute to a harmless level the toxic contaminants.
Mine-induced seismicity is also another hazard. According to the National Institute for Occupational Safety and Health (NIOSH), many fatalities in underground mines related to explosives were caused by miners being too close to the blast.
Fly-Rocks: Workers struck by rocks, either because they are too close to the blast or because the rock is thrown much farther than expected, remains one of the main causes of accidents both in surface or underground mines.
Explosives Fumes: According to the Dangers of Toxic Fumes from Blasting, surface mine blasters are far more complacent about fumes as those in underground mines. This is because there is a general belief that the open air would cause the fumes to disperse. But toxic fumes can be hazardous regardless of where they occur.
The explosive products used in surface and underground blasting operations produce a variable quantity of toxic gasses. Harmful concentrations of such gasses are more likely to appear in underground confined environments.An efficient, well designed and maintained ventilation system is key to preventing or mitigate this risk.
Premature Blast: This can be due to carelessness or be accidental. Faulty wiring and fuses can also be the cause. The explosive or pyrotechnical products that remain on the ground or in the muck pile might be triggered by any mechanical effect during the digging, milling or crushing stages of the mining process, causing injuries or fatalities to blasters or operators.
Although policies and safety measures continue to be updated to ensure disasters do not take place in mines around the world, there are still precautions the industry can take to ensure hazards are minimized and workers are kept safe.
It goes without saying that we need air to live and breathe. The air we breathe on the surface is a mixture of several gases including oxygen, nitrogen, argon, carbon dioxide, and other gases in trace amounts. We breathe easiest with 21% oxygen present in the air. When other gases contaminant the air, the oxygen levels drop, and that is when the trouble begins. The air in mines can be contaminated by the presence of other gases such as carbon monoxide, hydrogen sulfide, methane, and excess of carbon dioxide. Due to being in a confined space these gases are not always able to disperse and can therefore build up in the mine, and due to their combustible, explosive, or toxic qualities this is a serious issue. These other gases are often referred to as mine damps. This name comes from the German word Dampf meaning vapour. Rather than one particular gas they are a toxic or explosive mixture of different gases that have a varying effect on human health and mine safety. These damps are produced or released during mining operations including drilling and blasting, by mining machinery such as diesel and gasoline motors, and by other means such as the decay of timbers, the aftereffects of mine fires, and chemical processes like oxidation. The most efficient way of preventing these gases in mines is the incorporation of high quality mining ventilation systems as well as the use of early detection devices. A dangerous mine atmosphere is one that is toxic or explosive and there are several damps that create this kind of atmosphere. They are:
Firedamp is a mining term for a set of explosive gases found in mines. Its mostly made up of methane and methane is often an interchangeable term when miners talk about firedamp. Methane (CH4) is a colourless, odourless, highly flammable, and highly explosive noxious gas. It occurs naturally in coal seams and shale deposits and is a major component of the natural gas that we burn for energy. Methane gas accumulates in pockets of the coal and adjacent strata naturally over millions of years and can be released as the coal is mined. As the pockets are penetrated by the mining machinery the gas seeps into the pit where explosive mixtures of methane can form. Methane has a density relative to air of 0.55. Because its much lighter than air it tends to accumulate at higher levels within enclosed spaces where little ventilation exists to disperse it. Methane is only combustible at levels between 4 and 16%. Below that range there isnt enough to be ignited, and above that range the mixture is too dense to be explosive. The riskiest level of methane in the air is said to be 9.5% where it finds the perilous balance. All it takes is a naked flame or a spark from a machine to cause an explosion when these levels of methane are in the air. Methane in sufficient quantities is also capable of displacing oxygen from the air and can cause asphyxia in humans who breathe it in. When humans do not receive enough oxygen to the brain it can cause headaches, nausea, dizziness, and can ultimately result in death when the oxygen concentration drops below 6%. It makes sense then to firstly avoid the build-up of this highly flammable gas. This is done through quality mine ventilation.
And secondly, any dangerous gases must be detected and monitored. This was often done through the use of a testing flame. Originally a candle with a naked flame would be an indicator of an unsafe atmosphere depending on the change to the flame tip. As you can imagine, a flame is a pretty clear means of ignition, so when it got too close to the gas explosions would take place. Following from this, the safety lamp was developed to provide the coal mines with a means of testing for gases while still being able to operate in potentially flammable or explosive air.
Black damp is the mining term for the suffocating mixture of carbon dioxide and other unbreathable gases that can build-up in mines causing poisoning, asphyxiation, and ultimately death if left untreated. Carbon dioxide (CO2) is a colourless, noxious gas that only gives off a slight acrid smell at higher concentrations making it very hard to identify through human senses. While not toxic in itself, once carbon dioxide is mixed with the air it reduces the available oxygen one can breathe. The early symptoms of blackdamp (drowsiness, dizziness, and light-headedness) are easily mistaken for simple fatigue however lethal doses will cause asphyxiation that can easily result in death within seconds. If there is 18% carbon dioxide in the air it can kill, levels as low as 3% can cause breathing difficulties with symptoms worsening as the percentage increases. Carbon dioxide forms through the decomposition of organic materials, such as rotting mine timbers, as well as through human and animal respiration. The coal itself, once exposed to the air of a mine, will begin to absorb oxygen and exude carbon dioxide. With a heavier density relative to normal air (1.53) carbon dioxide will accumulate in lower-lying areas within the mine. The accumulation of black damp in a mine is caused predominantly by poor ventilation however other factors can be attributed such as the temperature, the amount of exposed coal, and the type of coal. The fact that blackdamp will always be present where coal is present and that it is hard to identify and distinguish between fatigue, increases the risk that warning signs will be missed allowing blackdamp to cause serious harm within seconds. Therefore prevention of black damp and identification of the dangerous gases is essential for mine safety.
White damp is a mixture of poisonous gases found in coal mines and is predominantly made up of carbon monoxide (CO). It is colourless, odourless, and tasteless making it very hard for a human to detect. It is commonly referred to as a silent killer. Carbon monoxide is a product of the incomplete combustion of carbon. In coal mines, large quantities of CO is generated during the oxidation of coal, and during mine fires or explosions. It will then be present in what miners call afterdamp - the resulting noxious gases given off by these fires, explosions, or blasting. Carbon monoxide is extremely toxic - it is absorbed by the haemoglobin in the blood blocking the ability of the haemoglobin to absorb and carry oxygen around the body, in turn, the body will begin to shut down. Carbon monoxide is also cumulative meaning that a person can be exposed for a number of short periods to no apparent ill effect, however, with each interaction the person will become more and more susceptible to its effect. If its levels get as high as 0.2%, death will take place within one or two hours. It is also highly flammable and explosive in mixtures with air between 12.5 and 74% with the most explosive concentration being 29%. And flames wont extinguish in its presence as it would with carbon dioxide. It is therefore one of the most dangerous gases found in a mine, and one of the most difficult to detect. Infamously, the domestic canary was used as an early warning against any noxious gases in the past. This is because carbon monoxide affects small animals more quickly than humans, and when exposed to carbon monoxide the bird would fall from their perch alerting the miners to move to safety. There is now modern equipment that can easily detect carbon monoxide without any cost to life.
Stinkdamp is the mining term given to hydrogen sulfide (H2S) due to its characteristic smell of rotten eggs. Hydrogen sulfide is a highly poisonous, flammable, colourless, and as mentioned, pungent-smelling gas. It has only ever been found in trace amounts in mines - but it can be lethal in even small concentrations. It is produced from the decomposition of iron pyrites in a mine due to the presence of water and how they interact. As mentioned H2S is a highly toxic gas capable of causing death in humans via asphyxiation. In lower levels, it will irritate the eyes, nose, and throat, as it increases it has a narcotic effect on the nervous system causing headache, dizziness and difficulty breathing. At higher levels of exposure H2S suppresses oxygen in the blood and tissues resulting in paralysis of the respiratory system and ultimately death in severe cases. Prolonged low exposure can lead to bronchitis, pneumonia, migraine, and loss of motor control. It can also form flammable mixtures in the air in the range of 4.5 - 45% where any sort of ignition would cause an explosion. With a heavy density of 1.9 it can accumulate in low points in the mine that are poorly ventilated. As always, the best way to prevent stinkdamp is proper ventilation and methods to test for the gases.
The most effective, safe, and efficient way of keeping mines free of dangerous gases is done through quality mining ventilation systems. Mine ventilation provides a safe flow of air through the workings of a mine at a measurable volume that dilutes and removes any build-up of dangerous gases and other chemical and physical contaminants that may be present, as well as regulating the temperature.
To create a thorough safe mining environment prevention must be supported by detection. Detection of dangerous gases in mines has changed and developed over the years with some techniques becoming traditions ingrained in the mining culture. The use of the canary has become a symbol for gas testing in mines, along with a testing flame, and the further developed flame safety lamps.
Did you know? A man, known as a fireman, penitent, or monk would edge forward with a candle on the end of a stick to test for the gases. If there was an explosion he was simply to keep his head down to allow it to pass over him - maybe not the safest means of detection.
While the canaries have gotten off lucky, and some safety lamps are still used today, there are now a sufficient range of detection devices, and means to detect gas including air samples, gas monitors and chemical analysis.
Undergrounds mining is still, even after hundreds of years of safety improvements, a dangerous and expensive business. Its wise for an investor to understand both the basic workings for an underground mine and the risks associated with underground mining. A bad mine disaster may not only kill miners; it can also bankrupt companies and close mines permanently.
Hard rock mines include most metal and diamond mines. They tend to be deep, and the orebody is often steeply inclined (or dipping). Shafts can be as a deep as several kilometres. Access from the surface is via a shaft or a decline. There is a variety of mining methods used, often in the same mine, depending on the geometry of the orebody and the stability of the rock.
Ore is broken up by blasting and drilling. Ore is then removed or mucked out by a LHD (load haul dump) machine, which resembles a low-profile articulated front-end loader. The ore may be dumped into a truck which then drives out via a decline, or ore may be dumped down a chute or ore pass to an underground crusher and then moved to a shaft using conveyer-belts, underground trucks or train either to a shaft, a horizontal adit or via decline direct to the surface.
The most common mining method is longwall mining which is largely automated using a self-advancing coal shearer including hydraulic roof supports 150-250m wide 1.5 -3m high extract panels roof collapses as machine withdrawals. This is the safest way to mine coal and shale as it requires no blasting in a potentially explosive environment.
A serious disaster can close a mine permanently. In the 2010 New Zealands Pike River Coal Mine disaster, not only killed 29 of the 31 miners underground, but also saw charges of manslaughter against mine management. It also bankrupted the mining company and the mine is unlikely to re-open.
In the same year, an explosion at Upper Big Branch Mine in West Virginia Massey Energys coal mine also had a death toll of 29 out of 31 miners. This incident saw a multi-million dollar compensation settlement. The mine will not re-open.
That both of these mines were coal mines is not coincidental. According to the US mine Rescue Association, of the 17 disasters in US mines since 1976, all but one has occurred in coal mines. Of those 16 accidents, 13 involved explosions, one was fire, one was oxygen-deficient air, and one was a stockpile collapse. Or in other words, mine ventilation is critical, particularly for coal mines.
Ensuring adequate ventilation is crucial in any mine, even more so in coal mines where the build-up of methane and other explosive and toxic gases is an on-going issue. Fortunately modern technology means that canaries used in Victorian coal mines as early warnings are now replaced by carbon monoxide gas detectors.
In hard rock mines, the ore itself doesnt give off lethal, explosive gases, but the exhaust fumes from vehicles do. In addition, the great depths that some mines reach, means that the geothermal gradient can see wall rocks as warm as 45C, making ventilation and air-conditioning necessary.
In mines with shafts, the shaft doubles as a downcast airway i.e. a source of fresh air being forced into the mine. Additional shafts are required for upcast ventilation for the remove of stale air; these can also be secondary or emergency escape routes.
Old historic mines are often more dangerous than newer ones. When I worked underground in Australia in the 1980s (a mine still in production), there were upper levels, which were either not mapped, or for which the maps had been lost.
Although the famous silver mines of Potosi, Bolivia, closed down officially some 150 years ago, to this day locals looking for some extra cash work the mine, and tourists are routinely taken down them, as well. The entire mountain is riddled with uncontrolled mining tunnels, all of which is unmapped and some of which is over 300 years old.
An unmapped, un-monitored level of a mine is dangerous because the dirt on the floor can be concealing a wooden or other cover to a deep winze (minor shaft from a level). Old mine workings are always propped by wood, and wood rots, so minor local collapses are to be expected.
In modern mines, most accidents occur, because of the juxtaposition of men and machinery in small, confined spaces. Tracked levels are safer as an approaching train is obvious, however, in untracked areas where electric vehicles are used, accidents do occur. Electric loaders and similar machinery are normally tethered by a thick power cable, which can break limbs or worse if the unwary visitor is caught out in the process of stepping over it; if you visit a mine always step ON such cables not over, the worst that can happen is that you get thrown clear.
The mining industry has a reputation of being ahazardouswork environmentwith riskspresentaround every corner.Employeesmusttakethe necessary precautions to mitigate these, sometimes, unavoidable risks and ensurethe safety oftheir own and others.
The key to staying safe is to identify and understand the risk and how to bestto proactivelymanage those risks.Thefollowingaresome ofthe most commonoperationalrisksthat arealmost habitual, and thereforeoften overlooked,intheminingindustry, andtheways to mitigate and manage them.
When preparing for work, noise is one of the common risks that minerstend tomiss. Thereareconstantly loud noises from drilling or heavy machinery, especially in underground mines which, over time, can cause hearing impairment. Although this risk is often difficult to avoid, its essential thatappropriatehearing protection iswornat all times,and companies should evaluate working conditions and exposurehoursthrough risk assessments.
Mining in open-pitoperations requires long hours of sun exposure. Significant exposure to UV radiation can lead to dehydration, headaches,nauseaor skin cancer.Itsimportant to use a combination of protection methods to combat the effects of this such as wearing a hat, applying sunscreen, and wearing protective clothing and sunglasses that filter the UV light.
Known as miners lung, another serious concern for miners is the inhalation of coal dust. Coal dustcausesshortness of breath, scarring of the lung tissue and ongoing respiratory issues.This operational risk can be controlled by providing respirators and the proper ventilation to prevent miners from breathing in too much dust,as well as conducting regular health monitoring on all employees.
Exposure to harmful chemicals can result in burns, respiratory problems andin theworst case, poisoning.In order toprevent this from occurring, mining companies should implement a standard operating procedure that addresses the correct use, handling and disposal of chemicals. This knowledge should be communicated across the board so all employeescan maintaincompliance.
There is a constant threat of explosion that occurs inunderground minesas flammable chemicals and gases are often running through the pipes. Its, therefore, important to ensure that the ventilation systems are checkedperiodicallyand warning signs are posted to remind employees of safe practices and procedures whilst working.
Mine site infrastructure has the risk of collapse or rocks and debris can become unstable and strike workers. Evacuation and escape plans should be practiced regularly so workers are confident in their role for when a cavein or collapseoccurs.
Although there are various other risks present on-site, these have been labeled the most common and dangerous to miners and their healthand well-being. Risks areever-present on-site and its important to ensure your employees are trained and prepared for the dangerous work to avoid any chance of unnecessary damages or risks occurring.
On top of finding ways to control these risks, a solution like INX InControl can help your employees become aware ofcommon risks in the workplace and how to avoid them in the future. By tracking and reporting all incidentsor risks that are present,your organisation can find better ways to carry out tasks that avoid exposure to these unnecessary risks.Simply enter anincident or established riskinto the system and key personnelwill be notified of any actions that need to be taken. With longer-term risks such as noise damageor miners lung, having specific training for employees will help them become aware ofthese risks that are likely to occuris important.INXInTuitionlets you set up and manage training coursesto ensureallemployees are remaining compliant with workplace standards.
Risks associated with health and safety of coal miners were investigated.A reliable methodology based on Fuzzy TOPSIS was developed to manage the risks.Three underground mines in Kerman coal deposit were selected as case studies.The model can help in taking appropriate measures before accidents can occur.
The scrutiny of health and safety of personnel working in underground coal mines is heightened because of fatalities and disasters that occur every year worldwide. A methodology based on fuzzy TOPSIS was proposed to assess the risks associated with human health in order to manage control measures and support decision-making, which could provide the right balance between different concerns, such as safety and costs. For this purpose, information collected from three hazardous coal mines namely Hashouni, Hojedk and Babnizu located at the Kerman coal deposit, Iran, were used to manage the risks affecting the health and safety of their miners. Altogether 86 hazards were identified and classified under eight categories: geomechanical, geochemical, electrical, mechanical, chemical, environmental, personal, and social, cultural and managerial risks. Overcoming the uncertainty of qualitative data, the ranking process is accomplished by fuzzy TOPSIS. After running the model, twelve groups with different risks were obtained. Located in the first group, the most important risks with the highest negative effects are: materials falling, catastrophic failure, instability of coalface and immediate roof, firedamp explosion, gas emission, misfire, stopping of ventilation system, wagon separation at inclines, asphyxiation, inadequate training and poor site management system. According to the results, the proposed methodology can be a reliable technique for management of the minatory hazards and coping with uncertainties affecting the health and safety of miners when performance ratings are imprecise. The proposed model can be primarily designed to identify potential hazards and help in taking appropriate measures to minimize or remove the risks before accidents can occur.