Cement-filled bags become new stopbank

Press, 18 November 1981, Page 1

Cement-filled bags become new stopbank

Nylon bags inflated with concrete are being used to underpin a retaining wall on the Avon River just upstream from the Carlton Mill Bridge. It is the first time the stopbanking method has been used in New Zealand. A 27m section of the old stone retaining wall has been undermined and is collapsing. endangering a footpath and curb-channelling on Carlton Mill Road. In the past, expensive concrete dams have had to be built to deal with similar subsidence.

With the new method, a simple trench is dug under the threatened riverbank, and planks are driven into the riverbed alonside. A nylon bag is then placed in the trench and pumped full of concrete, providing a stopbank. An engineer of Humes Industries, Mr Kevin Fogarty, said the job on the Avon would cost only $5200 compared with double that for an ordinary dam. The concrete dried in the bag, and so there was no

need to build any dry boxing, he said. His company, had bought the rights to the American “Fabriform” process. Mr Fogarty expected the process to be used widely because of its low cost .and effectiveness.-. A 27m bag, Im in diameter and divided into three sections, has been used for the Avon stopbank. But Mr.Fogarty said the bags come in all shapes and sizes, and could be used as pipeline jackets and for breakwaters, groynes, shoreline protection, and . structural repairs. •’