206
R.H. Charlier and Chr. P. De Meyer
Case examples of breakwaters and sea-walls adapted for specific sites, in Great
Britain, have been discussed by R.B. Thorn and A.G. Richards (1981, Sea
de fence and coast protection works : London, Thomas Thelford). Others of
relatively recent date, in Spain and in The Netherlands (IJmuiden) are described
by N. De Meyer and P. Soete (1970, Golfbrekers met talud : hun berekening,
vormgeving en uitvoering : Gent, Rijksuniversiteit, Fac. Toegepaste Wetenschappen). More recently P. Bruun and S. Kjelstrup (1981, Practical views on the
design and construction of mound breakwaters : Coast. Engng 5, 171-192), L De
Rouck (1991, De stabiliteit van stortsteengolforekers. Algemeen glijdingsevenwicht. Een nieuw deklaagelement : Leuven, Katholieke Universiteit Fac.
Toegepaste Wetenschappen) and J. Goda (1985, Random seas and design of
maritime structures : Tokyo, Univ. of Tokyo Press) provided good reviews and
some new ideas on design and stability of rubble mound breakwaters (Fig. 11).
De Rouck studied in depth the HARO, mentioned in this text.
Some reservations concerning the use of HARO blocks may validly be made : the
cost is not slight. However, the block has a good hydraulic stability and is light
weight ; this allows a smaller size, consequently a thinner layer, thence a grater
porosity and a cut in quantity of concrete of roughly one third. The reduced
weight permits use of a smaller crane thus of a narrower dam. Finally a lower
dam crest is only needed (fig. 21).
If the HARO provides greater linking facility and far higher hydraulic stability,
even greater resistivity to thermic variations, it has a somewhat lesser wave
reflection coefficient and wave run-up than the traditional concrete cube. The
best coefficient of run-up is apparently reached by accropods (0.95 vs. 0.85).
In comparative cost units of an armor layer, dolos and accropods run around 75,
tetrapods 90, against 70 for the HARO, the grooved cube being taken as the 100
basis.
In the long run utilizing HAROs proves economical.
Breakwaters come in a great variety. Land-backed structures can be either smooth
(concrete, stone pitching) or rough (randomly piled rockfill). Rough structures
dissipate wave energy strongly because they are permeable. Concrete
constructions have been occasionally perforated to reach the same result. Toe
depth dictates the speed of approach of the water, thus orbital velocity of particles
on impact, which is quite important.
R.H. Charlier and Chr. P. De Meyer
Case examples of breakwaters and sea-walls adapted for specific sites, in Great
Britain, have been discussed by R.B. Thorn and A.G. Richards (1981, Sea
de fence and coast protection works : London, Thomas Thelford). Others of
relatively recent date, in Spain and in The Netherlands (IJmuiden) are described
by N. De Meyer and P. Soete (1970, Golfbrekers met talud : hun berekening,
vormgeving en uitvoering : Gent, Rijksuniversiteit, Fac. Toegepaste Wetenschappen). More recently P. Bruun and S. Kjelstrup (1981, Practical views on the
design and construction of mound breakwaters : Coast. Engng 5, 171-192), L De
Rouck (1991, De stabiliteit van stortsteengolforekers. Algemeen glijdingsevenwicht. Een nieuw deklaagelement : Leuven, Katholieke Universiteit Fac.
Toegepaste Wetenschappen) and J. Goda (1985, Random seas and design of
maritime structures : Tokyo, Univ. of Tokyo Press) provided good reviews and
some new ideas on design and stability of rubble mound breakwaters (Fig. 11).
De Rouck studied in depth the HARO, mentioned in this text.
Some reservations concerning the use of HARO blocks may validly be made : the
cost is not slight. However, the block has a good hydraulic stability and is light
weight ; this allows a smaller size, consequently a thinner layer, thence a grater
porosity and a cut in quantity of concrete of roughly one third. The reduced
weight permits use of a smaller crane thus of a narrower dam. Finally a lower
dam crest is only needed (fig. 21).
If the HARO provides greater linking facility and far higher hydraulic stability,
even greater resistivity to thermic variations, it has a somewhat lesser wave
reflection coefficient and wave run-up than the traditional concrete cube. The
best coefficient of run-up is apparently reached by accropods (0.95 vs. 0.85).
In comparative cost units of an armor layer, dolos and accropods run around 75,
tetrapods 90, against 70 for the HARO, the grooved cube being taken as the 100
basis.
In the long run utilizing HAROs proves economical.
Breakwaters come in a great variety. Land-backed structures can be either smooth
(concrete, stone pitching) or rough (randomly piled rockfill). Rough structures
dissipate wave energy strongly because they are permeable. Concrete
constructions have been occasionally perforated to reach the same result. Toe
depth dictates the speed of approach of the water, thus orbital velocity of particles
on impact, which is quite important.