Details Given Of Taihape Deviation

Press, Volume CV, Issue 30979, 8 February 1966, Page 22

Details Given Of Taihape Deviation

■ (New Zealand Freu Association; TAIHAPE, February 7. The Ministry of Works, in a display which drew crowds at the Taihape Show on Saturday, released details of the UtikuMangaweka deviation, where extensive earthworks have already been carried out o few miles south of Taihape.

It is believed that this is the first time these details have been made available to the public, and Mr M. Faulls, the department’s senior engineer at Taihape, said that he had not seen the material used elsewhere.

The department describes it as “a project of national significance,” saying it “will be one of the greatest civil engineering projects undertaken in the development of the nation’s transport system.”

| The work will consist of ,fiur and a half miles of devirtion of State Highway 1 and ,1 le main trunk railway invol v|hg four high and lengthy ’bridges carrying both road aid rail traffic.

I “The present highway is a Host steep and devious route between Mangaweka and Utiku and is subject to constant troubles and delays due to slips and drop-outs,” the department says. “Maintenance costs for this section of the highway have always been extremely heavy. The deviation will reduce the distance along the highway by four miles, with travelling time reduced by. up to half an hour for heavy vehicles.” “Tortuous” The department describes the present route as tortuous, with sub-standard gradients and curves and situated in most unstable country. The new highway will reduce gradients to about 1 in 200 and curves generally will be on a radius of 80 chains, compared with the present 10. Six railway tunnels of restrictive dimensions will be eliminated, and the steel viaduct at Mangaweka will become redundant, with a big saving in costs. The department says that

the painting of the 946 ft long Mangaweka viaduct today costs considerably more than the total cost of the complete construction in 1904.

The Ministry of Works, in its information material, said: “In addition to the above benefits, the deviation will have a prestige value in the eyes of the world in its daring and unusual solution to a problem of massive proportions. Four Bridges This solution lies in the design of the four road-rail bridges which will make 1 lajor crossings of the Rangit kei river, the Kawhatau r ver and the Toe Toe stream. LUI four will have a deck ll’vel of approximately 250 ft above the normal river level, !as the rivers are deeply ent enched between nearly ver--1 cal walls of sandstone and siltstone. The width of the bridges will be 48ft lOin, carrying the North Island main trunk railway on a single track and State Highway 1 on a sealed width of 24ft. AU the bridges will be concrete, both prestressed and reinforced.

Bridge lengths will be: South Rangitikei 1240 ft (440 ft spans), Kawhatau 2120 ft (400 ft spans), North Rangitikei 750 ft (516 ft span), Toe Toe 260 ft (163 ft span). The department says that the four bridges will contain about 57,000 cubic yards of concrete. The great prestressing cables in the structures will have a total of 2120 miles, approximately twice the length of both islands of New Zealand.

The “free cantilever” erection method is to be used for the bridge superstructures. Segments are built out from supporting piers and progressively prestressed back, becoming self-supporting. It is a method which is becoming increasingly more popular, the department says, and is already being used bn the Newmarket viaduct at Auckland, the Hamilton railway bridge across the Waikato and the Buller river bridge at Longford, near Murchison. The entire project is being planned and designed by the Ministry of Works for the Railways Department and the National Roads Board, who will jointly finance the work, costing, according to the Ministry of Works, in the vicinity of £4 million. Tenders will be called for the bridges towards the end of the year, and the project' should be completed by 1971.