Basal filters beneath breakwaters and containment dykes

4 Basal filters beneath breakwaters and containment dykes 

The presence of breakwaters and containment dykes in marine environments can result in water turbulence at the toes and along the base of these structures, especially if they are constructed of rock bll. This can cause scour beneath the toes, undermining the structure and resulting in instability. To prevent scour and undermining of the breakwater or containment dyke, a geotextile biter is placed across the base of the structure, as shown in Fig. 20.16. Where breakwaters and containment dykes are located on rock or on overconsolidated clay foundations, base scour does not arise however, when the foundation consists of sand, and in particular loose sand, base scour can become a major problem. 

To enable the efficient installation of the basal geotextile biter on the seabed before construction of the breakwater or containment dyke, commonly the geotextile is brst formed into large panels onshore and then combined with a semirigid lattice of timber or bamboo. This combined structure is known as a fascine matttess and is the modern version of an old technique in which fascines (brushwood) were interwoven into a sheet to provide foundation protection for old dyke mounds. The fascine mattress is 

Lindo et al. (1993) and Pilarczyk and Zeidler (1996) describe the design and construction of a series of offshore breakwaters to prevent beach erosion at Kerteh Bay along the east coast of Peninsular Malaysia. Kerteh Bay had experienced severe coastal erosion as a result of wave attack during the annual northeast monsoon season. The erosion had become so severe that the sea had encroached to the boundary of a major 

After Lindo, M.H., Heijboer, D., Hassan, N.M.K.N., 1993. Coastal Erosion — the Kerteh Case, Possible Measures and Selection of the Most Suitable Concept. Van Oord, Gorinchem, The 

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