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Coastal Engineering: Theory and Practice
determined from linear wave theory, Dean and Dalrymple (1991). However, more commonly the structure will need to resist the impact of breaking or broken waves. The most widely used formula for estimating the
static and dynamic forces in this situation is based on Goda (see Burcharth in Abbott and Price (1994) for a review). However, high localized
shock forces may also arise due to breaking waves trapping pockets of air,
which are rapidly compressed. The study of this phenomenon is an ongoing area of research and currently there are no reliable formulae for the
prédiction of such forces. The works of Allsop et al. (1996) and Bullock
et al. (2000) provide some recent results. Several breakwaters are constructed using large blocks of rock (the “armour units” ) placed randomly
over suitable filter layers. At locations, wherein large natural rocks is scanty,
they are being replaced by numerous shapes of massive concrète blocks
(e.g., dolos, tetrapods, CoreLocs, accropods, etc.) size of which dépends
on several inter-related factors, like, wave height, armour unit type and
density, structure slope and permeability. Traditionally, the Hudson formula that expresses the weight of the armour unit proportional to H3 has
been widely used. This was derived from an analysis of a comprehensive
sériés of physical model tests on breakwaters with relatively permeable
cores and using regular waves. More recently (1985-1988) these équations
hâve been superseded by the formula of Van der Meer (2011) for rock
breakwaters.
8.2 Non-breaking Wave Forces
A vertical imperméable wall obstructs the kinetic energy in the waves a
major portion of which is reflected and some spent in the wave run-up
over it. The upward component of the energy over the wall can resuit
in the wave crests to rise to double the incident wave in deeper waters.
The downward component causes severe érosion and scour that would
lead to the instability of the structure if proper toe protection is not
provided.
Several analytical and laboratory and field investigations hâve been
undertaken to develop formulae for predicting the dynamic pressure on
walls due to waves. However, most of the formulae are based on monochromatic regular wave of constant height and period. Critical cases such as
non-overtopping vertical wall, overtopping vertical wall, vertical wall with
rubble foundation and non-overtopping vertical wall with different water
depth on both sides are briefly discussed in this chapter.
Coastal Engineering: Theory and Practice
determined from linear wave theory, Dean and Dalrymple (1991). However, more commonly the structure will need to resist the impact of breaking or broken waves. The most widely used formula for estimating the
static and dynamic forces in this situation is based on Goda (see Burcharth in Abbott and Price (1994) for a review). However, high localized
shock forces may also arise due to breaking waves trapping pockets of air,
which are rapidly compressed. The study of this phenomenon is an ongoing area of research and currently there are no reliable formulae for the
prédiction of such forces. The works of Allsop et al. (1996) and Bullock
et al. (2000) provide some recent results. Several breakwaters are constructed using large blocks of rock (the “armour units” ) placed randomly
over suitable filter layers. At locations, wherein large natural rocks is scanty,
they are being replaced by numerous shapes of massive concrète blocks
(e.g., dolos, tetrapods, CoreLocs, accropods, etc.) size of which dépends
on several inter-related factors, like, wave height, armour unit type and
density, structure slope and permeability. Traditionally, the Hudson formula that expresses the weight of the armour unit proportional to H3 has
been widely used. This was derived from an analysis of a comprehensive
sériés of physical model tests on breakwaters with relatively permeable
cores and using regular waves. More recently (1985-1988) these équations
hâve been superseded by the formula of Van der Meer (2011) for rock
breakwaters.
8.2 Non-breaking Wave Forces
A vertical imperméable wall obstructs the kinetic energy in the waves a
major portion of which is reflected and some spent in the wave run-up
over it. The upward component of the energy over the wall can resuit
in the wave crests to rise to double the incident wave in deeper waters.
The downward component causes severe érosion and scour that would
lead to the instability of the structure if proper toe protection is not
provided.
Several analytical and laboratory and field investigations hâve been
undertaken to develop formulae for predicting the dynamic pressure on
walls due to waves. However, most of the formulae are based on monochromatic regular wave of constant height and period. Critical cases such as
non-overtopping vertical wall, overtopping vertical wall, vertical wall with
rubble foundation and non-overtopping vertical wall with different water
depth on both sides are briefly discussed in this chapter.