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Silt curtains are impermeable vertical barriers extending from the seawater surface to their designed depths. The curtains are held in a vertical position by the carrier float on their top and a curtain weight at their bottom. A tension cable is designed at the carrier float to resist stresses incurred by currents. Moreover, the silt curtains are anchored to the seabed to hold them in the designed configuration.
Settlement in reclamation area occurs as a result of primary consolidation (i.e. by dissipation of excess pore water pressure) and secondary compression which involves creep of soils. Creep of soils occurs by viscous squeezing out of absorbed water in double layers of clay particles and rearrangement of clay particles under loading.
There are two advantages of adopting marine fill over mud extracted from land borrow area:
(i) In some land borrow areas, it involves breaking up of rock to suitable sizes for reclamation and the production rate is not high. With modern equipment for dredging and placing marine fill, the filling rate is much higher.
Filling below mean sea level usually has a low density. The settling sand in standing water would form a loose skeleton leading to a low density. However, as the sand level is rising, the increased load causes reallocation of sand grains in lower layers.
For geotextiles used in reclamation, they serve mainly the following two purposes:
(i) they separate reclamation fill from marine mud;
(ii) they may act as reinforcement to enhance the stability of reclamation.
However, the reinforcement function is still under heated debate because its performance as reinforcement depends on several factors like the directional strength of woven geotextiles and damage effect by installation of vertical band drains.
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