Factors affecting selection of tunnelling methods in greywacke terrain

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Gulliver, C.P. 1977 Factors affecting selection of tunnelling methods in greywacke terrain. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EG 283 7 p.

Abstract: This report discusses factors affecting the choice of excavation methods in 'drill and blast' tunnelling through greywacke rock in which steel rib or timber blocking is used as a primary support. A common basis for contention is the selection of excavation methods and primary support requirements that are appropriate to the rock conditions often encountered. A question which often arises is whether excavation should proceed using 'fullface' or 'top heading and bench' methods to achieve most satisfactory rate of progress with acceptable safety and quality of work. Comments made here are based on experience gained by engineering geologists of the NZ Geological Survey who have been involved in the driving of tunnels for the Tongariro and Rangipo Power Projects. Several of these tunnels are located almost entirely within interbedded argillite and greywacke sandstone which comprises the Kaimanawa Mountains. While the views expressly apply specifically to these rock types many of the general comments are also applicable to tunnelling in other kinds of rock. (auth)