MINING AND QUARRYING TRENDS 11 
 
fore, hole alignment is very fast, because it does not depend upon the position
or direction of the rig itself. Besides drilling according to the preprogrammed
pattern, the Datamaticcan also be operated with coordinated or direct control.
With coordinated control, the driller positions the booms in the desired
direction while the computer calculates the boom joint positions. If, as
occasionally will happen, it is impossible to collar the hole in the predetermined
position because, for example, it coincides with a rough promontory on the
face froi~i which the bit slips, the driller can manually move the boom to
a new position and press a button. The computer will then automatically compensate
for drill direction so that the hole terminates at the same predetermined
point. A visual display unit also aids the operator by continuously showing
boom alignments, penetration rates, and drilling patterns, including the
holes that have been and are to be drilled. The operator thus has a visual
check on the proceedings, permitting him or her to alter pressures, rotation
rates, and drifter positions to maximize productivity. 
Montabert, a French manufacturer, developed a fully computerized jumbo, Robefore,
that automatically controls the various drilling functions in a drilling
cyc1e.~ After a 2-year test program, an operational machine has been installed
in the Arbed iron mines in France. In addition to providing fully automatic
drilling capability, the jumbo offers accurate special feed positioning to
about 200; hole collaring positioning to about 2.5 inches; a traveling speed
from hole to hole of about 10 seconds, compared with 24 seconds during mar~ual
operation; smoother boom movements because speed is progressive; and improved
drilling efficiency. The basic boom movements are recorded by means of sensors.
These sensors direct the gathered data to a computer that controls the boom
cylinders. Using the same microprocessors, other functions are also computerized,
such as boom auxiliary movements (extension and feed anchoring), automated
control of the drilling phase (feed advance and retraction), drifter regulation,
control of safety parameters (oil level and temperature, etc.), as well as
other safety devices to avoid boom interference. After having positioned
the rig and the booms, the operator selects the required drilling pattern,
which is fed into the computer. There is no other human intervention during
the drilling cycle. The operator, how- 
ever, can manually take over the entire drilling cycle or continue to drill
on a semiautomatic basis. In the latter case, the boom is maneuvered and
positioned automatically, but hole collaring is controlled by the operator.
When drilling conditions require a change, new programming must be introduced
into the computer~ 
 The Tround Blast Hole Drilling System, a new hard-rock drill that can perform
at rates ranging from two to four times faster than a conventional drill,
was tested with the cooperation of a major oil company at a gas well in Arkansas
in formations consisting of hard sandstone and shale.8 The test results were
viewed as positive. Based on a technology known as the Open Chamber System,
the drill involves multiple projectile cartridges fed into and ejected from
a novel arrangement of firing chambers. This arrangement, along with the
complete elimination of the reciprocating breech element of conventional
guns, makes possible extremely high rates of fire, if required. The drill
utilizes multiple projectiles, which when fired in salvo, do not impact simultaneously,
but produce delays measured in millionths of a second owing to slight variations
of projectile weight and gas dynamics. Against rock, this rapid secession
of impact generates shattering shock waves ahead of conventional drill bits.

 Underground Mining.—Faced with a chronically depressed domestic*
mining
economy, surviving operations have been forced to curtail their work force
and improve productivity. In nearly all operations, this has involved major
changes and the development of new methods and techniques. moo Ltd. of Canada,
a company that operated at a loss for the 3 years prior to 1984, is a typical
example of the changing mode of operations that characterize today's mine
management.9 In a priority program to reduce costs, the company established
a formal mine research department with a broad mandate to develop easier,
safer, and more productive mining systems. The initial focus of this program
was directed toward ground control, stoping methods, and equipment development.
Basic ground control research and the application of rock mechanics to bulk
stoping systems were determined by Inco to be essential tools in the development
of efficient mining methods at greater depths. As a result, numerical modeling
techniques are being used to design the mining geometry, sequence, and destressing
program required to produce