TEKAPO POWER SCHEME

Press, Volume LXXVII, Issue 23300, 9 April 1941, Page 3

TEKAPO POWER SCHEME

; tunnel to be begun SOON

INGENIOUS MACHINES AND METHODS

The hydraulic shields which are to be used for the driving of the tunnel for the hydro-electric power scheme at Lake Tekapo are now being hunt in the Temuka workshops of the Public Works Department. The first of the two shields, which will drive the tunnel by a method entirely new to New Zealand, will be assembled underground within the next five or six W The S satisfactory progress that has been made with the preparatory work at Lake Tekapo was described yesterday by Mr T. G. Beck, district engineer to the Public Works Department, in an interview with a reporter of “The Press." The driving of the tunnel, obviously, cannot be begun from the bottom of the lake itself, a na the starting point at this from the bottom of a tunnel, about 70 feet deep, sunk beside the lake. This tunnel has now been driven almost its , full depth, and a start has been made with the enlargement of the chamber in which the shield will be assembled. At the other end of the tunnel line the chamber has already been enlarged sufficiently. ~ ~ From these two chambers the shields will be driven forward by hydraulic jacks, while automatic machinery, operated from inside them, bites into the earth and rock and prepares the way for a further advance of the shields. The tunnel will be 6000 feet long and 20 feet 4 inches in diameter. Even more ingenious will be the method of building the tunnel lining. As each shield advances it will leave behind, temporarily, a skin of metal. Inside this will be assembled a circle of concrete blocks. With each three feet of progress a new ring of blocks will be bolted on to the preceding one Each block, three feet long and 14 inches thick, will weigh 19001b and, with 13 to each circumference of the tunnel. 26,000 will be used in the full length. It has been estimated that this method of construction will save 2.500;000 feet of timbering. The building for the block-making plant is now well advanced. Mr Beck said, and the department is’ getting ready to call tenders for the casting of the iron moulds in' which the blocks will be made.