MOVING TUNNEL

Greymouth Evening Star, 4 November 1944, Page 4

MOVING TUNNEL

MR SEMPLE’S STATEMENT

CHRISTCHURCH, November 3. After a personal inspection of the Three R Tunnel, a short tunnel just south of Oaro, the present southern terminus of the South Island Main Trunk line, the Minister of Works. Mr Semple, is optimistic that the present movement of + hc tunnel towards the sea can be arrested within reasonable time, and al not too great a cost.

Mr Semple said that this tunnel was short and small, going through a spur. The county above it, on a hillside, was all broken, where slips had taken place, and it was full of “greasy backs.” The cause of the movement of the tunnel was due entirely to water filtering through this porous country. A report from a geologist, who had examined the country, stated that water was the cause of the trouble.

“The main thing is that the tunnel is not out of alignment.” said Mr Semple. “There, are several small cracks, which are due to extreme pressure, and not to faulty construction. Where the tunnel is cracked there are no signs of bulging, but just slight cracks here and there. There is reinforced concrete 18 inches to two feet think in the tunnel, but no thickness of concrete would resist a general movement.” Mr Semple added that the safety of the tunnel had not been impaired, but he had not wanted to take any risks. Goods trains were now passing through the tunnel, but he was not prepared to allow passenger trains to pass through until a final decision had been made as to how to prevent the movement continuing. His own view was that the trouble could be solved by putting a small tunnel paralled to the main tunnel, and half-way along; and then building on the incline, up to the centre of the water catchment area to lead the water away. He intended to discuss the matter fully with the Department’s engineers when he returned to Wellington. “These troubles are not new in this country,” said Mr Semple. “They have happened in many places in the North Island, and in some tunnels we have had movement for years before the country settlad down The trouble I wit hthe blue slip on the South I Island Main Trunk looked insurmountable at one time, but we got over that difficulty.” ‘4