- 行业: Mining
- Number of terms: 33118
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- Company Profile:
The U.S. Bureau of Mines (USBM) was the primary United States Government agency conducting scientific research and disseminating information on the extraction, processing, use, and conservation of mineral resources.
Founded on May 16, 1910, through the Organic Act (Public Law 179), USBM's missions ...
True topaz of a brownish-yellow color obtained in Colorado, but quartz similarly colored is sometimes sold under the same name.
Industry:Mining
Tube inserted in pulp at regulated depth, through which compressed air is gently bubbled. The air pressure indicates the pulp density and provides a means of control.
Industry:Mining
Tube projecting into central vortex of hydrocyclone or dense medium cyclone through which the classified fines or lighter specific gravity fraction of pulp leaves the system.
Industry:Mining
Tumbling of sands with sufficient violence to remove loosely adherent surface coatings without otherwise breaking down the particles to any great extent.
Industry:Mining
Tunnel-support systems made of steel are roughly of five types: continuous rib; rib and post; rib and wallplate; rib, wallplate, and post; and full circle rib. (1) A continuous rib system is usually made in two pieces for maximum speed of erection, lowest first cost, and lowest erection cost. Sometimes used in three or four pieces to meet special conditions and the following methods of attack: full face, side drift, and multiple drift. (2) A rib and post system is employed with the following methods of attack: full face in tunnels whose roof arch makes an angle with the sidewall; multiple drift and side drift in tunnels of such large size that two-piece continuous ribs cannot be shipped and/or handled; and heading and bench and top heading for support in the drift (with truss panels) for early support to roof. (3) In a rib and wallplate system, the rib is also usually made in two pieces for maximum speed of erection, lowest first cost, and lowest erection cost. It is sometimes used in three or more pieces to meet special conditions and with the following methods of attack: heading and bench, top heading, and full face. This type is esp. applicable to circular and high-sided tunnel sections where only a light roof support is needed. (4) In a rib, wallplate, and post system, these elements of support are used with the following methods of attack: heading and bench and top heading--for quick support to a roof; side drift--in large tunnels with bad rock conditions requiring quick support; and full face--for favorable rock where support is not needed tight to the face, for a tunnel whose roof makes an angle with the sidewall, and where post and rib spacing differ; and (5) A full circle rib--this method is used with the following attack: full face-- in tunnels in squeezing, swelling and crushed rock, or any rock that imposes considerable side pressure, also where bottom conditions make it impossible to carry roof loads on foot blocks, and in earth tunnel conditions sometimes encountered in rock tunnels; and heading and bench--under earth tunnel conditions with joints at spring line. The inverted strut is used where mild side pressures are encountered and also to prevent the bottom from heaving. A full circle with ribs closely spaced is heavily lagged for heavy loads associated with squeezing conditions.
Industry:Mining
Turbines used for driving coal cutters, belt conveyors, and similar duties. They are not so efficient in their use of the air as piston engines, but possess the merits of extreme simplicity and robustness, and therefore are preferred for coal face use.
Industry:Mining
