Mining_Methods_UnderGround_Mining - Mining and Blasting

el TenienTe, CHile
Traditional block caving layout.
in the 1800s. Exploitation first began in
1819, when the highest-grade minerals,
from what became the Fortuna sector,
were mined manually and transported on
animals to the coast. In 1904, William
Braden, an American engineer, founded
the first El Teniente company, Braden
Copper Company, and built a road for
carts and a concentration plant.
In 1916, Braden Copper became a sub-
sidiary of the Kennecott Corporation,
which was able to supply the funds necessary
to expand the mine. Kennecott
operated El Teniente until 1971. In April,
1967 the Chilean Government acquired
a 51% interest in the property, and founded
the Sociedad Minera El Teniente.
Following this agreement, major mine
expansion was undertaken, and a new
concentration plant was built in Colón,
which increased total production capacity
to 63,000 t/day. Full nationalization
followed in 1971, and El Teniente mine
became a fully state-owned company.
In 1976 Codelco was formed, and El
Teniente became part of it.
reserves
In total, the El Teniente orebody measures
2.8 km-long, 1.9 km-wide, and 1.8
km-deep. Schematically, the deposit is
formed around a central, barren, breccia
pipe of 1.0 to 1.2 km diameter, surrounded
by a mineralized rock mass.
The bulk of the mineralization within
the orebody is typical of massive, homogeneous
copper porphyries. In fact, El
Teniente is one of the largest porphyry
deposits of copper in the world. The main
rock types of the deposit are: andesite
73%, diorite 12%, dacite 9% and breccia
6%. At some time during its history,
the deposit was affected by supergene
alteration through percolation of meteorological
water close to surface, which
gave rise to secondary mineralization.
This secondary ore is high in copper
grade, but weak, and of good fragmen-
tation and caveability. In contrast, the
deeper primary mineralization is relatively
low in copper grade, harder, and
of moderate fragmentation and caveability.
As can be appreciated, secondary
ore and primary ore require very different
approaches in terms of mining.
Mining method
El Teniente produces some 334,000 t fine
copper and 4,720 t molybdenum each
year. Mass caving methods are employed
to deliver approximately 98,000 t/day
of ore to the mill from several sectors
underground, each sector being, in effect,
a large mine in its own right. This case
story focuses on the Esmeralda Sector,
which is set to become the most important
section of the mine, producing
45,000 t of the 130,000 t/day planned
for El Teniente.
Since El Teniente began operations
in the early 1900s, several exploitation
methods have been used, though the se-
condary mineralization was ideally suited
to conventional block caving.
However, the last mining sector lo-
cated in secondary ore, Quebrada
Teniente, was exhausted in 2003, and
all current mining is in primary ore
for processing at the expanded Colón
concentrator.
El Teniente started large-scale mining
of the primary ore in 1982, using
LHDs and the fully mechanized panel
caving method. The essential difference
between panel caving and conventional
block caving is that the former is a dynamic
method in which the undercut is
being continuously developed, and
drawpoints incorporated at the extraction
front, rather than being fully developed
before caving is started. This
method has been broadly successful at
El Teniente, and close to 250 million t
of ore have been extracted using panel
84 underground mining methods