Basal reinforcement beneath breakwaters and containment dykes

5 Basal reinforcement beneath breakwaters and containment dykes 

Breakwaters and containment dykes must maintain their shape and height over their required design life. If the foundation cannot support the breakwater or containment dyke loading, this can lead to deformations, settlements and ultimately instability of the structure. The preferred location for the construction of breakwaters and containment dykes is on good, stable foundations. However, in certain circumstances this may be impossible and foundation improvement techniques may have to be used when the foundation alone cannot support loading of the overlying structure. 

For large and critical breakwaters, it is the convention to dredge any soft foundation soil deposits and replace them with sand fill before construction of the breakwater on top. Alternatively, extensive (and expensive) foundation improvement techniques are 

One technique to improve the stability of breakwaters and containment dykes con-stmcted on soft foundations is to use geotextile reinforcement across the base of the stmcture (Fig. 20.19). This basal reinforcement technique has been used successfully for many years in the onshore construction of embankments on soft foundation soils, and is discussed in detail in chapter Geotextiles used in reinforcing foundations. Because of its cost—benefits, this technique has also been used in marine engineering structures over the past 20 years. 

The geotextile reinforcement is placed on the seabed with the granular fill placed on top. To install the geotextile reinforcement efficiently, it is commonly formed into large panels onshore and then installed on the seabed using the fascine mattress 

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