Which of the following tasks is not associated with surface mining?
A) Miners dig tunnels in the earth
B) Supports and pillars are used to support the mine roof
C) Additional interconnecting passages are dug
D) Explosives are used to move quantities of earth away from the deposit
Explanation: A) Incorrect. These tasks are generally associated with underground mining: 1. Miners dig openings (tunnels) in the Earth. Depending on the deposit's location in relation to the surface, tunnels may be vertical, horizontal, or sloped. Tunnels serve one of two purposes: (a) allow miners to reach the deposit, extract the mineral, and transport it to the surface, or (b) act as ventilation, allowing fresh air into the mine. 2. Supports and pillars of unmined ore are used to support the mine roof. 3. Additional interconnecting passages are dug. 4. Ore is removed from the deposit and taken to the surface using shuttle carts, rail cars, conveyor belts, or other methods. 5. Ore is crushed (usually on site) and then hauled away for processing. 6. When all of the ore that can be practically be extracted has been removed, the mine and its surrounding area are restored to original condition.
B) Incorrect. These tasks are generally associated with underground mining: 1. Miners dig openings (tunnels) in the Earth. Depending on the deposit's location in relation to the surface, tunnels may be vertical, horizontal, or sloped. Tunnels serve one of two purposes: (a) allow miners to reach the deposit, extract the mineral, and transport it to the surface, or (b) act as ventilation, allowing fresh air into the mine. 2. Supports and pillars of unmined ore are used to support the mine roof. 3. Additional interconnecting passages are dug. 4. Ore is removed from the deposit and taken to the surface using shuttle carts, rail cars, conveyor belts, or other methods. 5. Ore is crushed (usually on site) and then hauled away for processing. 6. When all of the ore that can be practically be extracted has been removed, the mine and its surrounding area are restored to original condition.
C) Incorrect. These tasks are generally associated with underground mining: 1. Miners dig openings (tunnels) in the Earth. Depending on the deposit's location in relation to the surface, tunnels may be vertical, horizontal, or sloped. Tunnels serve one of two purposes: (a) allow miners to reach the deposit, extract the mineral, and transport it to the surface, or (b) act as ventilation, allowing fresh air into the mine. 2. Supports and pillars of unmined ore are used to support the mine roof. 3. Additional interconnecting passages are dug. 4. Ore is removed from the deposit and taken to the surface using shuttle carts, rail cars, conveyor belts, or other methods. 5. Ore is crushed (usually on site) and then hauled away for processing. 6. When all of the ore that can be practically be extracted has been removed, the mine and its surrounding area are restored to original condition.
D) Correct. These general tasks are associated with surface mining: 1. Explosives are used to move quantities of earth away from the deposit. 2. Workers use large earth-moving equipment to move away layers of dirt and rock covering the deposit. 3. When the deposit is exposed, workers use smaller earth-moving equipment to lift and load the ore from the deposit into trucks. If necessary, explosives might be used to break down the deposit further. 4. The ore retrieved is often crushed on site and then transported to a nearby facility for processing.
You might also like to view...
What type of detail drawings are prepared with one part per sheet?
What will be an ideal response?
What are proportional controls?
A) Proportional controls regulate the starting and stopping of the system to keep the run time ratio as low as possible. B) Proportional controls increase or decrease the output of a controlled device in proportion to the level of the measured condition. C) Proportional controls have the ability to measure the controlled variable and the system output and dynamically adjust the setpoint to achieve more precise control. D) Proportional controls integrate the signals from several sensors and control the system operation based on the proportion of sensors requiring conditioning.
A 220 ? 1/2 W resistor has burned open, so you look in your parts box to find a replacement. Which one of the following resistors could you use to repair the circuit?
A) 220 ? 1/8 W B) 2200 ? 1/2 W C) 220 ? 1/4 W D) 220 ? 1 W
An increase of resistance must cause an increase of current.
Indicate whether the statement is true or false.