Tunnel taken cautiously

Press, Volume CXIV, Issue 33516, 23 April 1974, Page 3

Tunnel taken cautiously

(N Z. Press Association)

TAURANGA, April 22. JKaimai tunnellers are working cautiously on the Matamata face—reopened last Thursday after remedial work on a section of swelling ground—because of the danger of rock falls.

When the face was closed by an industrial dispute about six weeks ago the tunnellers were working on the heading and bench system in difficult ground. The Ministry of Works ' resident engineer on the project (Mr J. D. Bennion) said that whenever .the face was closed the rock tended to become looser, and great caution was needed when tunnelling resumed to avoid falls. Water flows at the face are high, and the ground

is swelling, so that when the bench section is removed and the tunnel opened to full diameter the same type of strengthened steel supports used in the 120 ft swelling section will be fitted. These are braced across the bottom to stop the pressure of the ground forcing them inward.

Mr Bennion expects progress to be slow while the tunnellers work through the major fault zone. On the Tauranga side, however, the Jarva tunnelling machine is making good progress. It bored 188 ft last week to take the face to 9708 ft. Mr Bennion has said he now believed the “holethrough” weill not be unit next February. There is less than one mile and a half to go.