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| Osarizawa Underground Mine Adit |
Osarizawa mine is an abandoned mine in Akita Prefecture,
Japan. Event though the mine is closed, the mine site is kept for sightseeing
purposes. The Osarizawa mine deposit is
a vein type deposit which was discovered in 708. The oldest Literature of
the mine was written in 1599 about the discovery of the Gojumaizawa gold
deposit which is part of the mine. The main commodities produced by the mine
were gold and copper.
The vein deposit was mined using the shrinkage stope mining method.
There are 15 levels and are 30m apart in height. The Total perimeter of the
mine levels is 700 km. The area of the mine site is 3km N-S by 2km E-W ~ 6km2 . Ceiling is 2-3m in
width.
The Level Zero starts at RL of about 300m and this is where the
access adit (ingress) is built. There are
5 levels above the zero level and 10
levels below zero level. The mining progressed upwards and mined materials were
collected at lower levels with the aid of gravity.
The host rock of the ore deposit is silicate mudstone which
is 10 times harder than concrete. Since the host rock is highly competent, the mine
was almost unsupported and less artificial support. Few supporting materials used
were logs/timbers of about 10mm to 300mm in diameter which were fitted well in between
mined out areas to prevent wall collapse. Other artificial supporting methods
are roof bolts, Mass wires and steel spiral cables drilled upwards to prevent
rocks from falling. Timbers are replaced every 10 years. The other supporting method used was the backfilling of
mined out areas with waste materials. Underground water is effectively under control
by plastic roofing gutters and drained out along the side of the concrete
pathway at each level.
The mined out ore/materials were transported by mini rail cars
which are powered by batteries. The rail cars were attached to one another like
train cars. The railways were built for these small battery powered rail cars. The
drilled or broken ores were loaded onto the rail cars and it required either
one or two operators to transport the materials out of the mine via shaft by
way of hoisting. At Zero Level the rail cars were driven out via the adit and
further to the processing plant for processing.
Production increased
with the increase in the rail cars.
Note:This article is an observation report and may not contain factual and detail information. The information here is kept at high level only. This article is subject to change if need be.
