28 July 2005
and where dredging is required to provide adequate water depths for vessels at
berths and approach channels, hydraulic fill is commonly used for land
reclamation because of its availability and low cost.
Hydraulic fill may be of good quality, consisting of granular materials, or may
consist of plastic organic silt, which is considered poor quality. When hydraulic
fill is used, the stability of the structure retaining the fill must be investigated,
taking into consideration the effects of adjacent surcharge loadings in addition to
the loadings from the fill. The placement of a select granular fill adjacent to the
retaining structure may be required if the hydraulic fill is of poor quality.
Hydraulic fill is in a loose condition when placed. To avoid fill settlements due to
loadings from other structures, stacked cargoes, and mobile equipment,
stabilization of the fill may be required. In areas of seismic activity, investigate
the liquefaction of hydraulic fills. Stability with regard to both settlements and
liquefaction may be enhanced by methods such as deep densification or by use
of sand drains. Material other than hydraulic fill should be used when the cost of
material obtained from onshore borrow areas is cheaper than the cost of material
obtained from offshore borrow areas or where good quality fill material is required
and is not available offshore.