Abstract
D.Ing.
The research described in this thesis is an investigation into
fundamental aspects of the mechanical excavation of hard rock
using free rolling cutters, currently being undertaken at the
Chamber of Mines of South Africa Research Organization.
The motivation for undertaking this study was provided by the
need to improve the effectiveness and operational efficiency of
this type of tool with regards to its application in the South
African gold mining industry.
Earlier work has shown that the use of high-pressure water jets
enhances the performance of mechanical cutting in hard rock.
To assess the potential of this approach for use in conjunction
with free rolling cutters, a series of laboratory tests was
conducted using both disc and button type cutters, to determine
the relative effects, on cutter performance, of variations in
the relevant jet and cutting parameters. The parameters
investigated were jet pressure, jet configuration, depth and
spacing of cuts and cutting speed. Jets of diameter 1,2 mm
were used singly and in combination of 2 and 4 jets at
pressures in the range of 5 MPa to 40 MPa which gave flow rates
of up to 0,3 lis per jet. Cut spacing, cut depth and cutting
speed were varied between 15 mm and 90 mm, 2 mm and 6 mm, and
0,1 mls and 1,0 mls respectively.
Tests were carried out on a linear rock cutting machine,
purpose built according to specifications prepared from
measurements made during underground field trials, which gave
it the ability to test full-scale cutters under loading
conditions representative of those found in the field. All the
tests carried out were performed in the constant penetration,
multiple pass (groove deepening) cutting mode, using dressed
(smooth) and pre-conditioned (pre-roughened) rock surfaces.