| Abstract | Lateral or inclined tunnels may be driven by conventional methods that involve drilling and blasting or by means of boring machines. Within the mineral industry, most lateral driving is done
conventionally whereas within the civil engineering field, an increasing number of tunnels are driven by mechanical devices. Inclined tunnels (raises) are, to an increasing extent, driven with raise boring machines which are gradually becoming more
competitive as compared with conventional methods. Machines for lateral tunnel driving generally operate by exerting a high thrust against rotary or disc cutters which are brought to bear against the rock face as the head of the machine rotates.
Performance on machine driving is rapidly gaining on conventional methods but some problems such as high cutter wear and machine inflexibility must be overcome. Thus far, lateral tunnels have been economically driven in rock with a compressive
strength of 25,000 lb/in2. Raises are usually bored by first completing a pilot hole then reaming to full size which may be 5 to 7 ft. in diameter. In rocks of up to 35,000 lb/in2 compressive strength which have been successfully bored, conventional
methods of driving would probably show more favourable costs. However, the superiority of bored raises for many purposes continues to favourably affect the spread of the technique. The superior types of openings which result from boring machines and
the efforts being expended on improvements, including steps towards automation, will probably further increase the applications for the new technology. |