Reappraisal of the geology and anticipated tunnelling conditions in Moawhango tunnel between Tongariro heading (CF 30 200') and Moawhango heading (CF 26 400')

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Hancox, G.T.; Paterson, B.R. 1975 Reappraisal of the geology and anticipated tunnelling conditions in Moawhango tunnel between Tongariro heading (CF 30 200') and Moawhango heading (CF 26 400'). Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EG 233 5 p.

Abstract: An increase in ground water inflow in Moawhango Heading from a fault zone recently encountered at construction footage (C.F.) 26,400' has overloaded the existing de-watering system. As a total of only 7,000 feet of excavation remains to be completed in this tunnel, a decision will have to be made on the feasibility of upgrading the de-watering system. As most large ground water inflows have been associated with fault zones, a reappraisal of the geology in the remaining system has been carried out to assist in planning for the remaining excavation. For this purpose faults encountered in the tunnel have been plotted and aerial photographs have been re-examined to predict the number and locations of possible zones of weakness that might be encountered. (auth)