Method for excavating a tunnel rock face by drilling a pattern of lifter and line holes
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United States of America Patent
Stats
-
Mar 4, 2003
Grant Date -
Nov 14, 2002
app pub date -
May 10, 2001
filing date -
May 10, 2001
priority date (Note) -
In Force
status (Latency Note)
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Abstract
A method for excavating a tunnel rock face by drilling a pattern of lifter holes and line holes. The line holes ensure the grade or slope of the excavation meets specification while reducing the need for cleaning out the face. A longitudinal band of lifter holes is drilled into the tunnel face at an acute angle in relation to the substantially perpendicular reference axis emerging from the tunnel face. A series of line holes, disposed opposedly adjacent to the lifter holes, are drilled at a smaller acute angle. The lifter holes are drilled deeper than the line holes and they do not intersect. Explosives are loaded into the lifter holes. The line holes are expendable and encourage fracturing of the rock.
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