DIGGING PILE HOLES

Press, Volume LXXXIX, Issue 27035, 9 May 1953, Page 2

DIGGING PILE HOLES

FRENCH PLANT ON BRIDGE WORK START MADE AT HOPE RIVER Imported at a cost of reported to be £43,000 in the expectation that it would revolutionise bridge building in New Zealand, a Benoto hammer grab is now undergoing its first testing work at the site of the new bridge over the Hope river on the Lewis Pass highway, 97 miles from Christchurch. The French invention was tested at Sockburn by the Ministry of Works before it was hired to the Paramount Building Company, the contractors for the building of the new two-way ferro concrete bridge to replace the. old wooden bridge across the Hope river. It then dug holes down into the shingle country at high speed, but it is experiencing severe “teething” trouble with big boulders. Two French operators who have visited many countries since 1947 demonstrating the Benoto are still at the Hope river showing two Ministry of Works trainees the working of the plant under all conditions. The purpose of the plant is to dig pile-holes and to reduce the work in foundation pile construction. It consists of a powerful winch operating the grab from a 20-feet high sheerlegs, or another piece of plant called a trepan to smash boulders, a five-feet diameter cylinder and a heavy machine which operates the oscillator to drive the cylinder into the ground. The Benoto is also a complete workshop, with plant to roll sections for the cylinder and to weld them. All the diesel motors are of English make. When the first eight-feet-hlgh section of the cylinder is placed on the site of the bore for the pile foundation it is grasped by the jaws of an oscillating arm worked on a hydraulically operated cylinder. As the arm oscillates, the steel cylinder bites into the earth and shingle and sinks. The grab, called a clam shell digger, is dropped into the cylinder and brings out the spoil when jt is raised by sheer arms and deposits it outside the sheerlegs. As the cylinder sinks, another section is welded on. Three Feet into Rock The first pile-hole at the Hope will be 20 feet deep, going down three feet into the rock. Big boulders have been encountered early and the trepan is being used to pound them into small pieces, which are lifted by the grab. The progress has been rather slow for the beginning. When the holes are driven into the rock, reinforced formes, made on the river bank will be dropped into toe cylinder and cut off at the required length. As the concrete is poured the cylinder is lifted. The Hope bridge will be 380 feet long and 16 piles will be built to carry it. The bridge will have seven spans, two of 40 feet and five of 50 feet When the construction reaches toe present main bed of the river, the Hope will be diverted and the pileholes will be dug in the bed. A swift rising river, the Hope has flooded once since the bridge work site was opened about three weeks ago, the water reaching to the level at which the Benoto was working yesterday morning. The bridge construction is expected to take 18 months. The building staff is working a 10-hour day for seven days a week, except for a week-end break every third week. A big improvement on the Lewis Pass route has been made by the opening of the long sidling diversion from the first series of sharp and steep turns after leaving the flat beyond the Hanmer Springs turn-off. The road has a good surface, as has the rest of toe highway to the Rahu Saddle, where the Highway Construction Company, .of Nelson, is widening and straightening the road through the bush. For a long stretch on the saddle, care has to be taken by motorists as the road is muddy and greasy. Keeping the highway open while they do the work has not made the job easier for toe contractors. The construction work is clearly sign-posted, a service appreciated by motorists after crossing the reading work being done south of the Hanmej torn-off.