Dam defending

The 335 m long, 71 m high rock fill embankment dam carries The Monaro Highway serving townships and major ski resorts in Australia. It is one of sixteen dams of the Snowy Scheme, which was comapleted in 1967 stors Water for irrigation and hydro power generation The Jindabyne units each contain 9 to 11 m-high inlet well shafts or “chimneys” down which water passes to tip the Fuse gates over during extreme floods.

Enerpac equipment involved in the project included CLRG 20012 high tonnage jacks, each offering up to 200 tonnes of force and 300 mm of stroke from a cylinder that can withstand side load forces up to 10% of rated capacity, without scoring.

The double-acting cylinders were used in sets of four to ensure high margins of safety and control in lifting eachfuse gate in steps, explained the company.

“The system also employed its new generation ZE 700 bar electric pump with fewer moving parts and less friction to run cooler than conventional pumps and require 18% less current draw,” explained Enerpac.

This was coupled to a 40 litre manifold with V82 manual control valves to provide secure load holding as shims were inserted beneath the load and cylinders at each stage of the lift. The system was employed to:

• Jack the eight Fuse gates 325 mm, in two stages, to remove prefabricated steel forms used to form the base chamber cavities.

• Check that no bond was formed during the casting of the Fuse gate between the base chamber beams and thesill.

• Weigh and check the centre of gravity of the Fuse gates so that design assumptions can be verified and the correct amount of concrete ballast used.

The 3 m high Fuse gate base chamber, constructed from steel formwork in four sections, had to be removed from each Fuse gate after concrete was poured. Each Fuse gate was, therefore, designed with four jacking points to permit lifting and removal of steel formwork.

Bill Hakin, Hydroplus Australia director, said, “The lift was done in two stages because of the 3.25 m lift required with the 300 mm maximum stroke available. The whole jacking and lowering sequence was specified to take no more than five hours and we had a fantastic run with it, no problems at all.

The whole system was simple and very cost effective, which was important in a project with high safety requirements and a tight budget.”