WORK ON one of the largest ever shore protection schemes has just started in Singapore. The Jurong and Tuas reclamation programme involves protecting 837ha of sand from erosion along nearly 17km of newly established shoreline.
The Jurong island project is part of an ongoing development, spanning some 3,000ha and due for completion by the 2015. It involves linking a cluster of seven small islets off the south western point of Singapore, mainly through land reclamation. Phase two, which is now in progress, calls for the reclamation of 440ha of land.
Jurong and Tuas Rock Contractors, the joint venture of Koon-Zinkon and Dredging International Asia Pacific, is carrying out the £32.5M coastal protection contract which is due to finish in mid-1999.
First stage is to profile the reclaimed slopes to give gradients of 1 in 3 and 1 in 4, with depths ranging from 4m to 18m. They will then be covered with geotextile, followed by 0.5m thick secondary and 1m thick armour layers of rock placed by a crane barge. Existing shore protection from the areas adjacent to the newly reclaimed shoreline will be dismantled and any suitable rock material recovered.
The geofabric, hand sewn into the desired length according to the depth of the toe and slope width, is rolled on to a drum held by wires at the top of the profiled slope. As the geofabric is rolled out, front loaders are used to cover it with rock down to the water line. Once in the water, the drum is attached to a frame secured to the crane barge. The frame is submerged and the unrolling process continues underwater as the crane barge draws away from the shore line, dropping rock on to the geofabric as it progresses.
The contract will use some 1.3M.m3 of non-woven geofabric and over 1M.m3 of rock. The rock, from quarries in Malaysia and Indonesia, is transported to site on flat top barges. Two grades are used, between 15kg and 60kg for the secondary layer and 150kg to 400kg for the armour layer.