Breakwaters cores

Rubble mound breakwater with a core made of geotextile sand containers... 

There are several reasons which might lead the engineer and other decision-makers in practice to use sand instead of conventional quarry run for the core of rubble mound breakwaters and structures, including among others ... 

In the following, only the case rubble mound breakwater with GSC-core in Fig. 12.17(a) is briefly addressed. Based on comprehensive hydraulic model tests performed in the twin-wave flumes of LWI, a comparative analysis of the two breakwater types was first performed with respect to wave reflection, wave transmission, wave runup, and wave overtopping performance. As a result, prediction formulae were proposed for the geocore breakwater and compared with those for the conventional rubble mound breakwater alternative. ... 

The fifth example study has shown that using sand encapsulated in geotextile containers for the core of rubble mound breakwaters, which is about one order of magnitude less permeable than a conventional core made of quarry run, may provide many advantages. This is particularly the case when rock material (quarry run) is... 

H. Oumeraci, A. Kortenhaus, H. Breustedt and P. Schley, Hydraulic model investigations on breakwaters with a core made of geotextile sand containers. Research Report No. 933, Report Leichtweifi-Institut fiir Wasserbau, TU Braunschweig (2007), pp. 71 and Annexes. 

These advances, together with numerous advantages of GSCs as soft rock, have contributed to extend the use of GSCs to permanent coastal defenses, including a wide range of types of structures such as seawalls, revetments, groins, artificial reefs, offshore breakwaters, perched beaches, dune reinforcement, core of rubble mound structures, scour protection, etc. (Fig. 21.1). 

The first phase of this research program which is concerned with hydraulic model tests to study in the twin-wave flumes of LWI the hydraulic performance and the armor stability of a rubble mound breakwater made of GSCs as compared to its conventional counterpart with a core made of quarry stones, has been completed... 

H. Oumeraci, A. Kortenhaus and K. Werth, Hydraulic performance and armour stability of rubble mound breakwaters with core made of geotextile sand containers — Comparison with conventional breakwaters, Proc. Int. Conf. Coastal Structures, Venice, ASCE (2007). 

In some cases, a specific rock grading is required or specified. In case sand or gravel fractions are not allowed, then the dredged rock will have to be screened. Dredged rock with a broad range in grain sizes is often used as core material for breakwaters. 

Fig. 20.23(a) shows a typical exposed breakwater consisting of a mbble core. This is the most common form of breakwater in which the exposed rock armour breaks up... 

Figure 20.23 Exposed breakwater with rubble core and equivalent with geotextile tube core, (a) Breakwater with a rubber core and (b) equivalent breakwater structure using geotextile tube core.

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