Tunnel Trouble At Atene

Press, Volume CIII, Issue 30528, 25 August 1964, Page 3

Tunnel Trouble At Atene

(N Z Press Association) WELLINGTON, Aug. 24. Rock Mechanics, Ltd., of London, has been engaged to work on the Wanganui river hydro-electric development investigations. The Minister of Works (Mr Allen) said today it was hoped information the firm would provide would lead to very substantial savings.

Mr Allen said by far the most difficult and costly problems associated, .with building a major dam at Atene were those of diverting the river by tunnelling through a 900 ft ridge of rock.

Work on a trial tunnel was already well under way, but the soft rock was behaving in an unexpected way, particularly where there were several hundred feet of rock overhead. “There is no doubt about the feasibility of driving the single big tunnel, or the several smaller ones, widely spaced, as originally envisaged,” he said. “Big savings can be made in the cost of the entrance and exit structures; however; if their distances apart can be reduced. “In addition it may well be

that the best, quickest, and most economical way of tunnelling will be by using a giant boring machine or ‘mole’ which can bore a hole 36ft in diameter. Such a machine has just completed a similar job in Pakistan. Mr' Allen said rock mechanics was a new science and the Government had decided to employ specialists qualified in this field. The. firm would use equipment to determine the state of stress and the elastic properties of the soft rock at the Atene site. Some additional trial tunnelling would be needed and the total cost of this and engaging the experts would be under £40.000. The estimated cost of the diversion works was in the vicinity of £3 million.