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Unformatted text preview: e removes the muck from the
face as shown in figure 10.3.
Using these heading machines it is possible to drive or construct large sized chambers or even the tunnels of large size can be driven in two lifts. The method is known
as ‘benching’. First upper bench is advanced in the upper half portion of the face and
then the lower follows it.
10.3 MILLING OR LONGITUDINAL (AUGUR) ROADHEADERS
In milling type roadheaders a cylindrical or cone shaped cutter head rotates in line with
the axis of the cutter boom (fig. 10.1(a); fig. 10.4).3 The cutting force is exerted mainly
sideways, which prevents utilization of full weight as counter force. When cutting harder
rock the machine is braced against the sidewalls with hydraulic jacks (‘stelling’). This
consumes time and the bracing jacks, who protrude side ways, make the machine inflexible in narrow headings. For wider and high tunnel faces, particularly in the hard rock,
these types of headers are unsuitable because their bracing jacks (stells) cannot reach
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- Spring '14