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F60، پل انتقال فوق سنگینی است که در معادن رو باز به کار گرفته می شود. این نقاله در عکس بالا بسیار عظیم به نظر می رسد. اما فکر می کنید بزرگی آن چقدر باشد؟ با نگاهی به شکل بالا و مقایسه این ابزار عظیم الجثه با برج ایفل، فهم ابعاد و اندازه آن کمی ساده تر می شود. این نقاله معدنی جمع و جور با ۵۰۲متر طول، ۲۰۲ متر عرض و ۸۰ متر ارتفاع، تنها ۱۱۰۰۰ تن وزن دارد! آیا این عکس شما را یاد چیزی شبیه کامیون های اسباب بازی کودکان نمی اندازد؟ در واقع شما شاهد یک کامیون معدنی کوماتسو سری 9xx هستید با این عکس اندازه این اسباب بازی غول پیکر بهت ر معلوم می شود. یک کامیون به ارتفاع ۷.۴ متر ک ه با بار، ۵۷۶۰۶۲ کیلوگرم وزن دارد. البته موتور آن با قدرت ۳۵۰۰ اسب بخار به راحتی از پس این هیکل گنده بر می آید. دستگاه حفاری معدن Bagger 288 بدلیل ظاهر ترسناکی که دارد، بیشتر شهرت اش را مدیون افسانه ی خطراتی است که بوجود آورده. اما به هر حال شما شاهد بزرگترین دستگاه متحرک دنیا هستنید! البته این ماشین حفاری چنان عظمتی دارد که می تواند یک کشتی را به راحتی به دو نیم کند و یا همانطور که در عکس می بینید، بولدوزری را بی هیچ دردسری همانند یک زردآلو قورت دهد.
ادامه مطلب
Steps of mine development
The process of mining from discovery of an ore body through extraction of minerals and finally to returning the land to its natural state consists of several distinct steps. The first is discovery of the ore body, which is carried out through prospecting or exploration to find and then define the extent, location and value of the ore body. This leads to a mathematical resource estimation to estimate the size and grade of the deposit. This estimation is used to conduct a pre-feasibility study to determine the theoretical economics of the ore deposit. This identifies, early on, whether further investment in estimation and engineering studies is warranted and identifies key risks and areas for further work. The next step is to conduct a feasibility study to evaluate the financial viability, technical and financial risks and robustness of the project. This is when the mining company makes the decision to develop the mine or to walk away from the project. This includes mine planning to evaluate the economically recoverable portion of the deposit, the metallurgy and ore recoverability, marketability and payability of the ore concentrates, engineering concerns, milling and infrastructure costs, finance and equity requirements and an analysis of the proposed mine from the initial excavation all the way through to reclamation. The proportion of a deposit that is economically recoverable is dependent on the enrichment factor of the ore in the area. Once the analysis determines a given ore body is worth recovering, development begins to create access to the ore body. The mine buildings and processing plants are built and any necessary equipment is obtained. The operation of the mine to recover the ore begins and continues as long as the company operating the mine finds it economical to do so. Once all the ore that the mine can produce profitably is recovered, reclamation begins to make the land used by the mine suitable for future use.
Mining techniques
Mining techniques can be divided into two common excavation types: surface mining and sub-surface (underground) mining. Surface mining is much more common, and produces, for example, 85% of minerals (excluding petroleum and natural gas) in the United States, including 98% of metallic ores.[22] Targets are divided into two general categories of materials: placer deposits, consisting of valuable minerals contained within river gravels, beach sands, and other unconsolidated materials; and lode deposits, where valuable minerals are found in veins, in layers, or in mineral grains generally distributed throughout a mass of actual rock. Both types of ore deposit, placer or lode, are mined by both surface and underground methods.
Processing of placer ore material consists of gravity-dependent methods of separation, such as sluice boxes. Only minor shaking or washing may be necessary to disaggregate (unclump) the sands or gravels before processing. Processing of ore from a lode mine, whether it is a surface or subsurface mine, requires that the rock ore be crushed and pulverized before extraction of the valuable minerals begins. After lode ore is crushed, recovery of the valuable minerals is done by one, or a combination of several, mechanical and chemical techniques.
Some mining, including much of the rare earth elements and uranium mining, is done by less-common methods, such as in-situ leaching: this technique involves digging neither at the surface nor underground. The extraction of target minerals by this technique requires that they be soluble, e.g., potash, potassium chloride, sodium chloride, sodium sulfate, which dissolve in water. Some minerals, such as copper minerals and uranium oxide, require acid or carbonate solutions to dissolve.[23][24]
Surface mining is done by removing (stripping) surface vegetation, dirt, and if necessary, layers of bedrock in order to reach buried ore deposits. Techniques of surface mining include; Open-pit mining which consists of recovery of materials from an open pit in the ground, quarrying or gathering building materials from an open pit mine, strip mining which consists of stripping surface layers off to reveal ore/seams underneath, and mountaintop removal, commonly associated with coal mining, which involves taking the top of a mountain off to reach ore deposits at depth. Most (but not all) placer deposits, because of their shallowly buried nature, are mined by surface methods. Landfill mining, finally, involves sites where landfills are excavated and processed.[25]
Sub-surface mining consists of digging tunnels or shafts into the earth to reach buried ore deposits. Ore, for processing, and waste rock, for disposal, are brought to the surface through the tunnels and shafts. Sub-surface mining can be classified by the type of access shafts used, the extraction method or the technique used to reach the mineral deposit. Drift mining utilizes horizontal access tunnels, slope mining uses diagonally sloping access shafts and shaft mining consists of vertical access shafts.
Other methods include shrinkage stope mining which is mining upward creating a sloping underground room, long wall mining which is grinding a long ore surface underground and room and pillar which is removing ore from rooms while leaving pillars in place to support the roof of the room. Room and pillar mining often leads to retreat mining which is removing the pillars which support rooms, allowing the room to cave in, loosening more ore. Additional sub-surface mining methods include hard rock mining which is mining of hard materials, bore hole mining, drift and fill mining, long hole slope mining, sub level caving and block caving
Safety
Safety has long been a controversial issue in the mining business especially with sub-surface mining. While mining today is substantially safer than it was in the previous decades, mining accidents are often very high profile, such as the Quecreek Mine Rescue saving 9 trapped Pennsylvania coal miners in 2002. The Courrières mine disaster, Europe's worst mining accident, caused the death of 1,099 miners (including many children) in Northern France on 10 March 1906. It seems that this disaster was surpassed only by the Benxihu Colliery accident in China on April 26, 1942, which killed 1,549 miners.[41] Government figures indicate that 5,000 Chinese miners die in accidents each year, while other reports have suggested a figure as high as 20,000.[42] Mining ventilation is a significant safety concern for many miners. Poor ventilation of the mines causes exposure to harmful gases, heat and dust inside sub-surface mines. These can cause harmful physiological effects, including death. The concentration of methane and other airborne contaminants underground can generally be controlled by dilution (ventilation), capture before entering the host air stream (methane drainage), or isolation (seals and stoppings).[43]
Ignited methane gas is a common source of explosions in coal mines, or, the more violent coal dust explosions. Gases in mines can also poison the workers or displace the oxygen in the mine, causing asphyxiation.[43] For this reason, the MHSA requires that workers have gas detection equipment in groups of miners. It must be able to detect common gases, such as CO, O2, H2S, and % Lower Explosive Limit. Additionally, further regulation is being requested for more gas detection as newer technology such as nanotechnology is introduced.
High temperatures and humidity may result in heat-related illnesses, including heat stroke which can be fatal. Dusts can cause lung problems, including silicosis, asbestosis and pneumoconiosis (also known as miners lung or black lung disease). A ventilation system is set up to force a stream of air through the working areas of the mine. The air circulation necessary for the effective ventilation of a mine is generated by one or more large mine fans, usually located above ground. Air flows in one direction only, making circuits through the mine such that each main work area constantly receives a supply of fresh air.
Miners utilize equipment strong enough to break through extremely hard layers of the Earth's crust. This equipment, combined with the closed workspace that underground miners work in, can cause hearing loss.[44] For example, a roof bolter (commonly used by mine roof bolter operators) can reach sound power levels of up to 115 dB.[44] Combined with the reverberant effects of underground mines, a miner without proper hearing protection is at a high risk for hearing loss[44].
Since mining entails removing dirt and rock from its natural location creating large empty pits, rooms and tunnels, cave-ins are a major concern within mines. Modern techniques for timbering and bracing walls and ceilings within sub-surface mines have reduced the number of fatalities due to cave-ins, but accidents still occur.[citation needed] The presence of heavy equipment in confined spaces also poses a risk to miners, and despite modern improvements to safety practices, mining remains dangerous throughout the world.
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ژيزمان:
كمياب ; آلمان غربي ، چك و اسلواكي ، ايتاليا ، انگليس ، هند ، برزيل ، امريكا و استراليا |
ادامه مطلب
نقشه پراکندگی اندیس های ایران
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