Parititahi SH 1 tunnels, Kaikoura - an engineering geological appraisal of remedial proposals

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Paterson, B.R. 1978 Parititahi SH 1 tunnels, Kaikoura - an engineering geological appraisal of remedial proposals. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EG 319 10 p.

Abstract: The twin Parititahi tunnels which are located on SH1 10 km south of Kaikoura, are presenting clearance problems for large trucks and trailers carrying maximum-sized loads. The problems are due to a curve in the northern end of the northbound tunnel and a restricted approach to the southbound tunnel. Several proposals are being considered for widening part or the total length of the northbound tunnel and extension of the sea wall. Additional proposals include excavation of an open cut and development of the northbound tunnel to two-lane width. Both tunnels are in greywacke which is unsupported except for portal structures and the curved section of the northbound tunnel. The greywacke in the tunnels is fractured by numerous, non-persistent and random rock defects which contribute to a lack of preferential rock breakage. Excavation of the rock should not be difficult because of the fracture pattern, but to ensure long term stability and minimise support it is recommended that disturbance of the tunnel walls and roof be kept to a minimum. A significant increase in the tunnel width may require the design and installation of a complete tunnel lining. A rock platform which surrounds the promontory should provide adequate foundations for extension of the sea wall.