SOUTH ISLAND MAIN TRUNK

Press, Volume LXXIV, Issue 22306, 21 January 1938, Page 10

SOUTH ISLAND MAIN TRUNK

♦ MAJOR ENGINEERING TASKS BORING OF AMURI BLUFF TUNNEL REVIEW OF PROGRESS OF BIG JOBS The boring of a 43-chain tunnel through the Amuri Bluff is the major tunnelling job in the completion of the South Island Main Trunk railway, and, according to -the District Engineer in Christchurch for the Public Works Department (Mr F. Langbein), it is the key to the opening of the line down the east coast of the South Island, from Picton to Bluff. On its completion, Mr Langbein said yesterday in a review of the major jobs involved in the construction of the line between I Parnassus and Wharanui, depended the opening of the line for through rail traffic. Major works in the construction of the railway, apart from the formation of the permanent way, include the following:— Leader bridge. Hawkswood cutting. Conway bridge. Amuri Bluff tunnel. Goose Bay tunnel. Kahautara bridge. Kohai bridge. Hapuku bridge. Shand's tunnel. Ohau tunnel. Sandy Bay tunnel. Blue Slip cutting. Clarence bridge. Kekerangu bridge. On the southern section of the line, between Parnassus and the Kahautara river, two important works completed are the Leader bridge and the Hawkswood cutting. Plate-laying has been carried to two miles beyond Parnassus. The next major work to the north is the bridging of the Conway, and this is nearing completion. Only four of its 17 piers remain to be concreted. The plate girders for the bridge, similar to those used in the Leader bridge, have been manufactured at the Hillside workshops, and when the railhead has reached the Conway they will be transferred from Parnassus and erected. 'Tunnelling Near Parnassus The boring of the first tunnel north of Parnassus is nearly finished. This tunnel is about one mile and a half beyond the Claverley homestead- The longest tunnel on the route is that through the Amuri Bluff.. Excavation of the approach at the southern end has been begun with a power shovel and a locomotive. Because of the treacherous nature of the country in this approach cutting it has been decided to extend the length of the tunnel by four chains, so that its length will.be 43 chains. No tunnelling has been commenced at this end, but at the northern end a bottom head has been driven 184 feet, and the excavation has been carried 162 feet. Concrete lining has been placed for 140 feet. It is estimated that it will take two years to complete the tunnel. Scraper equipment will be used in the tunnel soon to make heavy shovelling unnecessary. Another tunnel commenced is just to the south of Goose Bay. This will be about 10 chains long. A bottom head has been driven 79 feet at the south end, but work will be accelerated when air-compression plant has been delivered. It is hoped that this plant will be in operation soon. Bridges Over Five Rivers Important work will be involved in the construction of bridges across the Kahautara, Kohai. Hapuku, Clarence, and Kekerangu rivers. A contract for the bridge over the Clarence has been let, and the foundations are about a third completed. Plans are being drawn for bridges over the other rivers. Good progress is being made with the Blue Slip cutting, which has al.Vvays been a source of trouble for tiie engineers. The Blue Slip is a great hill of badly broken and waterladen clay about four miles south of i Wharanui. It was recognised as a major engineering problem when the line was first being constructed seven years ago. for the movement of the clay continually broke the formation and twisted the temporary lines. But now the engineers consider they have conquered the menace of this moving pug. There are numerous tunnels to be driven on the northern section, and good progress is being made with those at Shand's, Ohau, and Sandy Bay. The length of these three tunnels is nearly half a mile, and about a third of the work has been done.