The Alaska daily empire. [volume] (Juneau, Alaska) 1912-1926, 1922-07-28
MINING METHODS
DEVELOPED HERE
CREATES NOTICE
Editor of Big Mining Journal
Says Bradley Solves I'm
possible" Problem.

The results of methods developed
and perfected by F. w. Bradley,
President and p r. Bradley, Cen
eral Manager of the Alaska Juneau
properties, in both the local mine
and mill are attracting considerable
interest among mining men every
where. according to- George J.
Young, an editor of the Engineering
and Mining Journal-Press, who left
this morning on the Princess Alice
for San Francisco. Mr. Young said
that these results indicate "a sue
cessful solution of a mining prob
lem that had all the earmarks of
being impossible
Mr. Young came here last week
to look over the mine and mill and
see for himself what is being done.
Virtually all of the time was spent
at the Alaska Juneau. In an in
tervew given a representative OF
The Empire just before his depart
ure, he said:
1T is an interesting and instruc
tive lesson for a mining man to
obtainan insight into the operat-
ing conditions of the Alaska Ju-
neau Gold Mining Company's mine
and mill Through the courtesy of
F. w. Bradley and his brother. P.
R. Bradley | was permitted to visit
the plant and mine OF this COM
pany.
Challenges Mining Engineers
THE deposit mined is a broad
zone impregnated with quartz
veins and of sufficient certical and
horizontal extent to challenge the
incentive of the mining engineer.
Selective mining of the quartz veins
is out of the question and this min
'ng problem is one Of breaking
the ore in large slopes at the least
possible cost. Mr. p r. Bradley
has developed a mining method
which is unique and which involves
features quite unusual in other min
ing operations.
The stope Is served by two drifts,
which connect series Of chutes
leading into the stope Above each
chute is a bulldozing chamber
through which the ore must pass
before it can be loaded from the
chute The floor of the BULLDOG
ing chamber is an inclined grizzl,
with openings between the bars
two feet in width. The bulldozing
chambers are connected by a drift
and crOsscuts so that convenient
access can be obtained. The bot
tom of the ore blocks above the
bulldozing chambers is undcrcut in
such a manner as to leave suoping
hopperlike floors in communica
ton with the inclined raises con-
Meeting with the bulldozing cham
bers.
Departs From Custom
"Up to this point the arrange
ments do not involve novel features
except in detail of working. To
break the ore-block above the un-
dercut portion presents several pos
sible methods. Shrinkage stopping
a common method, was a POSSIBLE
ity, but required drilling and blast
ing to such an extent as to involve
prohibitive cost Mr. Bradley de-
velooped a vertical retreating meth
cd which obviated the need Of the
miners working directly in the
stope. This method consists OF
series of raises extending to the
upper levels and accessible from
them.
"These raises are placed at in
tervals in the ore body and from
them short crosscuts are driven at
more or less regular vertical inter
walls The crosscuts aredriven as
small as possible and the ends of
the crosscut nearest undercut
charged with powder. the charges
ranging from 1900 to 5000 pounds in
weight. These blasts break the ore
body down above the undercut por-
ton. The lower ore is drawn
through to the bulldozing chambers
and the large pieces drilled by
STOPPER and jackhammer and broken
by blasting to a size sufficiently
small to pass the grizzly Suffic-
lent broken ore is left in the stope
to support the walls.
Low Working Costs Obtained
"An extremely low powder ratio
and a minimum of labor expendi-
ture is obtained by this method.
The powder ratio is one-third OF a
pound of powder per ton broken.
Most OF this powder is required
in bulldozing operations. The to-
tai cost of mining including tram
ming is slightly over 10 cents per
ton and of this the labor cost is
slightly over IL cents per ton. This
is a remarkable result under the
conditions.
1.-THE ore is loaded into trains
Of 10-ton cars. 40 cars to the train