21
APPENDIX – HARD ROCK MINER’S
HANDBOOK EXCERPTS
de la Vergne, J.N., 2008, Hard Rock Miner’s Handbook,
Ed. 5, Stantec Consulting Ltd., Phoenix, AZ, ISBN
0-9687006-1-6, pp. 330.
Section 10.2 Rules of Thumb
The maximum rate at which ready-mix concrete will be
poured down a 6-inch diameter slick line is 60 cubic yards
per hour. Source: Marshall Hamilton (pg. 93)
To diminish wear and reduce vibration, the boot
(“velocity killer”) at the bottom end of the concrete slick
line should be extended in length by 6 inches and the
impact plate thickened by one inch for each 1,000 feet of
depth. Source: R. N. Lambert (pg. 93)
Section 10.3 Tricks of the Trade
To reduce segregation of concrete poured down a slick line,
“grease” the line with half a ready-mix truckload of grout
before starting the pour. Source: Bob Dengler (pg. 94)
The most practical way to handle the unavoidable seg-
regation of concrete poured down a slick line is to wet the
empty line and then direct the first concrete to the shaft
bottom. After less than one cubic yard is wasted, the shaft-
men can plainly see that segregation has ceased and direct
the remainder of the pour into the forms. Source: Tom
Goodell (pg. 94)
Section 10.7 Shaft Concrete (pg. 96)
The ready-mix concrete required for the shaft lining is low-
ered in the shaft by one of two means:
• Concrete bucket (similar to those used in surface
construction), or
• Slick line (a vertical pipe that is extended as the shaft
deepens).
The slick line was first used in South Africa to enable
concrete to be poured at the same time that the shaft bot-
tom is mucked out. There, the concrete mix was adjusted
to have a smaller coarse aggregate size for it to flow freely
in a six-inch diameter pipe installed with flanged connec-
tions. The problem of segregation was largely overcome by
installing a boot (‘velocity killer”) at the pipe bottom that
provides some re-mixing of the concrete. Today, the flanges
are replaced with Victaulic ® style “low-profile” couplings
and, in some cases, the slick line diameter is increased from
6 to 8 inches to accommodate a larger aggregate size.
The following two characteristics of concrete dropped
down a slick line should be noted.
• As a slug of concrete falls, it creates a vacuum behind
it that sucks out moisture explaining why the slump
(measured at the collar) is reduced at the shaft
bottom.
• As the concrete drops, its loss of potential energy is
converted to heat explaining why the temperature of
the concrete (measured at the collar) is increased at
the shaft bottom.
Shaft contractors today are divided in opinion as to which
method is best to use. In hard rock mines, the concrete
quality is normally not critical (refer to Chapter 9 -Shaft
Design) and so the slick line is usually satisfactory. An
important consideration is that the slick line may later
become very useful to the mine. A slick line may be desired
to deliver ready-mix concrete or shotcrete mix required for
initial and ongoing construction underground after the
shaft is sunk.
A common misconception is that the slick line must
be hung perfectly vertical. The slick line must be installed
perfectly straight and the easiest way to do this is to hang it
vertically with plumb lines. When a slick line is installed (or
partly replaced) in an already existing shaft, the procedure
is to align the pipe column with straight lines anchored at
each end, not with plumb lines.
Section 10.7.1 Coriolis Effect (pg. 97)
The ready-mix concrete (that free-falls in the slick line) does
not tend to fall perfectly vertically instead it rubs against
the East wall of the pipe due to Coriolis effect (the tangen-
tial velocity of the earth due to rotation is greater at the
shaft collar than it is deep in the mine). While this phe-
nomenon is not significant to placement of a slick line, it
confirms that perfect verticality is not a requirement. The
Coriolis effect is important in other aspects of mining (such
as drift of tailropes and dropping material down a vertical
raise or borehole). The drift, x off the vertical is easily calcu-
lated with the following formula:
x =2/3 w[2h3/g] 1/2 cosγ
In which
x =Horizontal drift, meters
w =angular velocity of the earth, radians/second
h= depth dropped, meters
g =acceleration of gravity, meters/sec/sec
γ =Latitude of the minesite, degrees
APPENDIX – HARD ROCK MINER’S
HANDBOOK EXCERPTS
de la Vergne, J.N., 2008, Hard Rock Miner’s Handbook,
Ed. 5, Stantec Consulting Ltd., Phoenix, AZ, ISBN
0-9687006-1-6, pp. 330.
Section 10.2 Rules of Thumb
The maximum rate at which ready-mix concrete will be
poured down a 6-inch diameter slick line is 60 cubic yards
per hour. Source: Marshall Hamilton (pg. 93)
To diminish wear and reduce vibration, the boot
(“velocity killer”) at the bottom end of the concrete slick
line should be extended in length by 6 inches and the
impact plate thickened by one inch for each 1,000 feet of
depth. Source: R. N. Lambert (pg. 93)
Section 10.3 Tricks of the Trade
To reduce segregation of concrete poured down a slick line,
“grease” the line with half a ready-mix truckload of grout
before starting the pour. Source: Bob Dengler (pg. 94)
The most practical way to handle the unavoidable seg-
regation of concrete poured down a slick line is to wet the
empty line and then direct the first concrete to the shaft
bottom. After less than one cubic yard is wasted, the shaft-
men can plainly see that segregation has ceased and direct
the remainder of the pour into the forms. Source: Tom
Goodell (pg. 94)
Section 10.7 Shaft Concrete (pg. 96)
The ready-mix concrete required for the shaft lining is low-
ered in the shaft by one of two means:
• Concrete bucket (similar to those used in surface
construction), or
• Slick line (a vertical pipe that is extended as the shaft
deepens).
The slick line was first used in South Africa to enable
concrete to be poured at the same time that the shaft bot-
tom is mucked out. There, the concrete mix was adjusted
to have a smaller coarse aggregate size for it to flow freely
in a six-inch diameter pipe installed with flanged connec-
tions. The problem of segregation was largely overcome by
installing a boot (‘velocity killer”) at the pipe bottom that
provides some re-mixing of the concrete. Today, the flanges
are replaced with Victaulic ® style “low-profile” couplings
and, in some cases, the slick line diameter is increased from
6 to 8 inches to accommodate a larger aggregate size.
The following two characteristics of concrete dropped
down a slick line should be noted.
• As a slug of concrete falls, it creates a vacuum behind
it that sucks out moisture explaining why the slump
(measured at the collar) is reduced at the shaft
bottom.
• As the concrete drops, its loss of potential energy is
converted to heat explaining why the temperature of
the concrete (measured at the collar) is increased at
the shaft bottom.
Shaft contractors today are divided in opinion as to which
method is best to use. In hard rock mines, the concrete
quality is normally not critical (refer to Chapter 9 -Shaft
Design) and so the slick line is usually satisfactory. An
important consideration is that the slick line may later
become very useful to the mine. A slick line may be desired
to deliver ready-mix concrete or shotcrete mix required for
initial and ongoing construction underground after the
shaft is sunk.
A common misconception is that the slick line must
be hung perfectly vertical. The slick line must be installed
perfectly straight and the easiest way to do this is to hang it
vertically with plumb lines. When a slick line is installed (or
partly replaced) in an already existing shaft, the procedure
is to align the pipe column with straight lines anchored at
each end, not with plumb lines.
Section 10.7.1 Coriolis Effect (pg. 97)
The ready-mix concrete (that free-falls in the slick line) does
not tend to fall perfectly vertically instead it rubs against
the East wall of the pipe due to Coriolis effect (the tangen-
tial velocity of the earth due to rotation is greater at the
shaft collar than it is deep in the mine). While this phe-
nomenon is not significant to placement of a slick line, it
confirms that perfect verticality is not a requirement. The
Coriolis effect is important in other aspects of mining (such
as drift of tailropes and dropping material down a vertical
raise or borehole). The drift, x off the vertical is easily calcu-
lated with the following formula:
x =2/3 w[2h3/g] 1/2 cosγ
In which
x =Horizontal drift, meters
w =angular velocity of the earth, radians/second
h= depth dropped, meters
g =acceleration of gravity, meters/sec/sec
γ =Latitude of the minesite, degrees