F. Land stabilization

Where the land being reclaimed abuts the seaboard, special protection measures are required to maintain the stability of the site. The type of structure used for this purpose will depend on the availability of land. In Singapore, sea revetments are constructed on specially placed sand fill (see figure 3.11) with flat slopes. Excavation behind these revetments needs to be carefully considered due to the groundwater table associated with certain high tidal conditions.

Where space is a premium, a concrete or steel sheet piled wall can be built to protect the filled area from erosion and reduce the land loss from flat batters.

Seawall design is at a specialist function and required the consideration of a large number of complex interacting factors to ensure the wall is structurally stable and does not cause more erosion due to the change in the natural seaboard conditions.

Inland sites which are close to large rivers or require major drainage impose severe constraints on construction. It is generally necessary to construct the principal drainage channels before the filling of the site. One technique for doing this is illustrated in figure 3.12 where the walls of the channel are built “in the dry” and the waterway excavated by dragline or dredge depending on the drain dimensions.

As can be seen from the foregoing discussion, reclaiming land requires detailed engineering analysis in hydrology, soil mechanics, maritime engineering and construction techniques for successful implementation. Without this input, the results have a serious impact on land outside the site and result in unstable conditions within the site for many years.

Figure 3.10. Predicted settlements in Singapore reclamation

Figure 3.11. Revetment shore treatment, Singapore

Figure 3.12. Technique for channel construction and land reclamation