An orthorhombic mineral, K2 SO4 .
A device consisting of a bit attached to knuckle-jointed rods used to
drill a curved borehole or branched holes from a parent borehole.
Syn:Thompson arc cutter
A furnace in which material is heated either directly by an electric arc
between an electrode and the work, or indirectly by an arc between two
electrodes adjacent to the material. ASM, 1
a. A portion of rock left standing at the intersection of a mine wall and
roof, to support the roof.
b. Curved roof of underground opening. See also:dome
c. A curved structural member used to span openings or recesses; also
built flat. Structurally, an arch is a piece or assemblage of pieces so
arranged over an opening that the supported load is resolved into
pressures on the side supports and practically normal to their faces.
ACSG, 1
d. A part of a furnace; a crown. ASTM
e. To heat a pot in a pot arch. ASTM
f. One of the five chambers of a brick kiln; also, the fire chamber in
certain kinds of furnaces and ovens. Webster 3rd
g. The roof of a reverberatory furnace.
Applied to the wooden voussoirs used in framing a timber support for the
tunnel roof, when driving a tunnel on the so-called American system. These
blocks are made of plank, superimposed in three or more layers, and a
breaking joint. Stauffer
Said of the rocks of the Archeozoic. AGI
Corn. Said of the roads in a mine, when built with stones or bricks.
The earlier part of Precambrian time, corresponding to Archean rocks. Also
spelled: Archaeozoic. AGI
Forms or patterns on which sprung arch bricks are laid to ensure the
proper arch contour.
A normal H-section steel girder bent to a circular shape. The usual form
consists of halves joined together at the crown by bolts and two
fishplates. The arch girder is usually splay legged or straight legged in
shape, but horseshoe shapes are also in use. See also:steel support;
wood stilt. Nelson
The statement in fluid mechanics that a fluid buoys up a completely
immersed solid so that the apparent weight of the solid is reduced by an
amount equal to the weight of the fluid that it displaces. AGI
a. Arch.
b. Curved support for roofs of openings in mines; constructed archways in
masonry.
c. The development of peripheral cracks around an excavation due to the
difference in stress between the skin rock and the rock in the stress
ring. See also:V-arching
d. The folding of schists, gneisses, or sediments into anticlines.
e. The transfer of stress from a yielding part of a soil or rock mass to
adjoining less yielding or restrained parts of the mass. ASCE
f. The fretting away of the periphery of a rock tunnel, usually converting
it from a rectangular to a circular or elliptical section. The effect in
the back is sometimes referred to as the "natural arch." The putting in of
a lining built to an arch shape should not be referred to as arching but
as "lining" or "putting in the arch." Spalding
The natural process by which a fractured, pulverulent, or plastic material
acquires a certain amount of ability to support itself partially through
the resolution of the vertical component of its weight into diagonal
thrust. Woodruff
See:V-arching
The main load-bearing member of a ribbed arch. Hammond
Steel assemblies used to support mine workings. Pryor, 3
See:abutment; pressure arch.
See:arkose
A method of refraction seismic prospecting in which the variation of
travel time (velocity) with azimuth from a shot point is used to infer
geologic structure. The term also applies to a refraction spread placed on
a circle or a circular arc with the center at the shot point. AGI
A group of basaltic and associated igneous rocks intermediate in
composition between rocks of the Atlantic suite and the Pacific suite.
CF:Atlantic suite; Pacific suite. AGI