Physics of Mining Essay -- physics mining miner

Mining is a necessary component of the world we live in and it has been practiced for thousands of years. The mining industry produces billions of tons of raw product every year. The process of mining is very complicated and involves plenty of physics! Two main components of the mine cycle are: Drilling, and Blasting. Some important factors in mining are the pillars, rock elasticity, and the slope stability of the ground being mined. A basic method for destroying rock is mechanically induced stress, such as drills and erosion jets. A turbine drill for example, uses a turbine to rotate a diamond faced cutter wheel. The power output, p, can be calculated using the equation p=2 Ï€NT where N is the rotational speed of the turbine and T is the torque on the cutter wheel. As the rotary speed increases, the torque decreases. The maximum power output of a turbine drill is when the rotary speed is between 5,000 and 10,000 rev/min. Erosion jets can be classified as low speed or high speed. The low speed jets use abrasive particles, such as sand to erode rock at 10 to 200 m/s and the high speed jets use water at 200 to 1,000 m/s. The high speed jets are used for the hardest rock and require pressures up to 5,000 kg/cm ²! In underground, non coal mining, the excavation of rock is done largely by conventional percussive drills. These break the rock by indentation. The drilling machine applies a force to the drill bit, giving it a velocity which hits the rock and causes it to break. The equation for the peak stress induced by the drill bit on the rock is as follows: ÏÆ' = Ï  cv, where ÏÆ' is the maximum stress induced, and Ï , c, and v are the density, compressional wave length, and velocity of the drill bit, respectively. In coal mining, ... ... Now there is an added force from the water called pore pressure and the normal force is decreased making the slope more likely to fail. The following diagram represents this scenario with 'W' as the gravitational force downward of the upper rock, 'p' as the pore pressure from the water, and 'A' as the area that the water affects. Mines are erected by pillars, which have factors of safety. The factor of safety is the average strength divided by the average stress ratio. When this ration falls below 1.00, there is pillar instability. If one pillar in a mine collapses, the result is greater force acting on the rest which in turn increases their stress and decreases their factors of safety. If all of the pillars are highly stressed, one pillar failure could lead to a domino effect and the collapse of a mine. 1.60 is considered a good factor of safety for pillars.