9781439834220.ch10

3 using these heading machines it is possible to

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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 b...
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