An H-section girder used as a roadway or face beam support. The girder for
spanning roadways is commonly 6 in (15.2 cm) deep and 5 in (12.7 cm) in
width of flange. It is supported by wood or steel props or by brick or
concrete sidewalls, the roof being made secure by timber or sheet lagging.
Channel section girders are also used in special cases.
See also:steel support
Aust. That straight portion of the inner main rail between the rails of a
turnout.
A lateral excavation into a thick seam of coal. Also called straight coal.
Standard, 2; Fay
A plain deflecting wedge, not equipped with a rose or stabilizing ring.
Long
An annular-shaped (core) bit the inner walls of which are parallel with
the outer walls and not tapered to receive a core lifter.
Syn:straight-side core bit
a. A reaming shell the outside walls of which are straight and not set
with diamonds or hard-metal reaming points. Long
b. Sometimes used as a syn. for blank reaming shell. Long
a. Narrow headings in coal. CTD
b. A method of working coal by driving parallel headings and then removing
the coal between them. CTD
a. Change in the shape or volume of a body as a result of stress; a change
in relative configuration of the particles of a substance.
Syn:deformation
b. Deformation resulting from applied force; within elastic limits strain
is proportional to stress. CF:stress
c. A measure of the change in the size or shape of a body, referred to its
original size or shape. Linear strain is the change per unit length of a
linear dimension. True strain (natural strain) is the natural logarithm of
the ratio of the length at the moment of observation to the original gage
length. Conventional strain is the linear strain referred to the original
gage length. Shearing strain (shear strain) is the change in angle
(expressed in radians) between two lines originally at right angles. When
the term strain is used alone, it usually refers to the linear strain in
the direction of the applied stress. See also:true strain
ASM, 1
d. There are, generally speaking, two kinds of strains: normal and shear.
Normal strains are those that may result in the relative displacement of
two particles along the line joining those particles, whereas in shear
strains, the particles are displaced at a right angle to the line joining
them. All possible deformations may be represented as a combination of
these two types of strain. Issacson
An instrument well suited for measuring the strain on a rock face. It
consists essentially of an invar steel bar with a fixed point at one end
and a movable point attached to a rider at the other end. The rider may be
moved along the bar between two stops, and the extent of movement is
indicated by a dial gage attached to the bar. Issacson
Fractures occurring in rock quarries where the rock is under compressive
stress. This stress is relieved locally in the process of quarrying,
resulting in the rending or fracturing of the rock mass.
Rock burst in which there is spitting, flaking, and sudden fracturing at
the face, indicating increased pressure there. Higham
See:slip cleavage
In elastic theory, a sphere under homogeneous strain is transformed into
an ellipsoid with this property; the ratio of the length of a line, which
has a given direction in the strained state, to the length of the
corresponding line in the unstrained state, is proportional to the central
radius vector of the surface drawn in the given direction. The ellipsoid
whose half axes are the principal strains.
CF:reciprocal strain ellipsoid
a. A general term for a device with which mechanical strain can be
measured, commonly by an electrical signal, e.g., a wire strain gage.
AGI
b. An electrical, mechanical, or optical device for measuring movement of
rock, cumulative loading of support props, opening cracks, etc.
Pryor, 3
c. An electromechanical device that transforms small displacements to
changes in resistance that are proportional to the displacement. Strain
gages are used in ocean bottom pressure measuring equipment. Hunt
A technique for the determination of absolute (total) strain and stress
within rock in situ. In this method, a smooth hole is bored in the rock
and a gage is inserted to measure diametral deformation. The hole is then
overcored with a large coring bit so that the cylinder of rock containing
the deformation measuring gage is free to expand. The change in the
diameter of the hole when the rock cylinder is free to expand is a
function of the original stress in the rock and its elastic modulus.
Woodruff
A technique for the determination of absolute (total) strain and stress
within rock in situ. This method involves (1) installation of strain gages
on the rock surface; (2) cutting of a slot in the rock between the strain
gages so that the surface rock is free to expand; (3) installation of a
"flat-jack" (hydraulic pressure cell) in the slot; and (4) application of
hydraulic pressure to the flat jack until the rock is restored to its
original state of strain. The original stress in the rock is presumed to
be equal to the final pressure in the flat jack. Woodruff
At any point on the surface of a stressed body, strains measured on each
of three properly chosen intersecting gage lines make possible the
calculation of the principal stresses at that point. Such gage lines, and
the corresponding strains, are called a strain rosette. Roark
a. A skeleton drawing of a structure, as a roof of truss or a bridge,
showing the stress to which each member will be subjected.
b. A quarryman's term for granite sheets produced by compressive strain.
See:false cleavage; slip cleavage.
One of the purest commercial forms of tin (99.89% purity) produced from
alluvial ores in Malaysia.