First Mining Drc-Zambia March -April 2020 digital edition First Mining Drc-Zambia March - April 2020 digital | Page 23

FEATURE
Foskor contracts Geomech Africa to
help optimise its North and South pits
F
oskor is a producer and
distributor of phosphate rock,
phosphate-based
fertilisers,
sulphuric acid, phosphoric acid and
magnetite locally and internationally.
The company is South Africa based,
with in excess of 1600 employees.
Foskor awarded Geomech Africa a
contract to carry out a geotechnical
investigation at its Mining Division
is in the Limpopo Province of South
Africa.
The image below shows
a simplified geological map of the
Phalaborwa Complex, with the mine
located in the North.
The current pit designs for Foskor’s
north and south pits were based
on very limited geotechnical data.
This lack of data results in pit slope
designs of low confidence.
A geotechnical risk assessment and
gap analysis of the South and North
pyroxenite pits was carried out in 2010
and it was concluded that a number
of oriented geotechnical boreholes
should be drilled to ensure that there is
sufficient discontinuity, rock mass and
intact rock strength data to identify the
continuity of the rock.
The main purpose of this drilling
programme is to obtain sufficient
geotechnical data for optimisation of
the north and south pits. The project
entailed drilling two holes in the
North pit and five in the South pit.
The holes which range from 300m to
500m deep are being drilled by LF90
Boart Longyear and CS1500 Atlas
Copco rigs whose long reach booms
are specially designed for exploration
drilling.
Down the hole surveys are done at
the end of each day to ensure that the
direction of the holes does not deviate
more than 2º from the required angle
of -70º. The survey tool is connected
to the overshot and dropped to the
bottom of the hole to read the direction
of the hole.
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