EAST COAST RAILWAY

Evening Post, Volume CXXVII, Issue 105, 6 May 1939, Page 13

EAST COAST RAILWAY

TUNNEL PROGRESS

TIKIWHATA AND WAIKOURA

Tunnelling on the route of the East Coast railway is being speeded up, and good progress generally has been made in the last twelve months. The indications are that the tunnels will be completed by the dates stated by the Minister of Public Works, the Hon. R. Semple, when he inspected the route some months ago. In an article this week, the "Poverty Bay Herald" states that over the whole section of the line between Gisborne and Waikokopu, tunnels aggregate 20,660 ft, there being 10 minor jobs of this nature which already have been pushed well on towards completion, while the greater portion of the footage is in the three main tunnels known as the Tikiwhata, Coast, and Waikoura tunnels.

The Tikiwhata has a total length of 9802 ft, and its completion is scheduled for October, 1940. The Coast tunnel should be ready by March, 1940, and the Waikoura, of 4730 ft, is already within measurable distance of completion.

The last-named job is now manned by only one tunnelling ga"ng, as the two faces are so close that to continue working on both might be an invitation to trouble. The gang taken from one of the heads has been placed elsewhere on the route, and the one gang retained is working south from Torries' Camp, and is expected to break through to the southern face next' week.

Different systems of working have been adopted according to the conditions met in the three main tunnels. In the Tikiwhata and Waikoura tunnels the American method of fullsection excavation has been followed. Under this method, the top bench is thrust forward, and space is made for the upper timbering. As work proceeds, the rock flanks are taken out and the roof timbers are given the support of pillars, as shown in the series of pictures on the illustrations page today. In the Coast tunnel, where the ground difficulties are much greater, the older method in use in New Zealand for a great number of years, and entailing the opening of the bottom heading as the initial operation, has been resorted to.

An indication of the progress made in recent months is given by figures made available by the engineer in charge of construction, Mr. W. L. Bell, who stated to a "Poverty Bay Herald" reporter that in the Tikiwhata tunnel the top heading had been opened up for an aggregate distance of 3675 ft of the 9802 ft length. Full-section excavation had been completed for 3567 ft, and the concrete lining of the tunnel was completed for 2690 ft. The rate of progress in recent weeks had been thoroughly satisfactory.

In the Waikoura tunnel the two faces were within 80ft of each other, and full-section excavation was well up to the faces, while the concrete lining also was well advanced.

Work on the Coast tunnel is not making the same progress, as there are special difficulties connected with this shaft, including the necessity for establishing what is % known as an invert, a slab of concrete which passes under the formation level and connects the two walls of the tunnel. This is necessary to counteract the effect of movement in the broken country pierced by the tunnel, and insure the work as a whole against damage. It is proposed that the lining of this tunnel will be carried out in conjunction with other work on tunnels further south.