202
CHAPTER 5. COASTAL STRUCTURE MODEL
which is easily applied to profile data. Van der Meer (1988) used thi
damage definition in his research on rubble-slope stability.
It is hard to say which method of damage evaluation is the best. Give
the variation in stability that is likely to arise between repeat tests, eithe
method probably gives similar estimates of damage. Nevertheless, regarc
less of what method is used to quantify rubble-mound structure damage,
is important to describe the method when reporting results.
5.2.6 Modeling Armor Unit Stresses
The most commonly used material for armor layer protection on rubble
mound structures is quarrystone. Quarrystone armor units are known t
break into smaller pieces occasionally; but for the most part, structui
damage or failure due to stress fracturing of armor stones is not considéré
a major problem.
However, as coastal engineering advanced and coastal structures wei
planned for deeper water, hydraulic stability considerations dictated large
armor units, often surpassing the maximum stone sizes the quarry cou]
produce. In other situations, structures were proposed in locations whej
no suitable stone source existed. For these reasons coastal engineers turne
to the use of artificial concrete armor units of various sizes and ge<
metric configurations. Examples include dolosse6, Tribars, Tetrapods, A
cropodes, and solid cubes. Fracturing is not an important consideratic
for the bulky armor units such as the Accropodes and cubes where on
shape, surface texture, and the armor unit specific gravity are importai
similitude considerations (Owen and Briggs 1985).
The term dolos is singular, and the plural is formed as “dolosse”.
The problem with concrete armor units arose as slender armor uni
were made larger and larger, and several breakwaters suffered extensi'
damage that was attributed to breakage of the slender units. Where
these structures had been proven to be hydraulically stable in physic
model tests, armor unit breakage in the prototype resulted in smaller, h
draulically unstable, armor units that lacked the size and interlocking fe
tures of the intact units. The problem was compounded by smaller piec
impacting other intact units, causing them to fracture.
Coastal structure designers recognized the need to determine stress le
els in concrete armor units in addition to hydraulic stability; however, tl
stress problem is stochastic in nature because of the randomness in loadii
and contact supports (Burcharth, et al. 1991). This makes analytical ai
numerical techniques extremely difficult to implement.
As field experience accumulated, it became apparent that the larg
slender armor units had little tolerance for movement. This led to desi
CHAPTER 5. COASTAL STRUCTURE MODEL
which is easily applied to profile data. Van der Meer (1988) used thi
damage definition in his research on rubble-slope stability.
It is hard to say which method of damage evaluation is the best. Give
the variation in stability that is likely to arise between repeat tests, eithe
method probably gives similar estimates of damage. Nevertheless, regarc
less of what method is used to quantify rubble-mound structure damage,
is important to describe the method when reporting results.
5.2.6 Modeling Armor Unit Stresses
The most commonly used material for armor layer protection on rubble
mound structures is quarrystone. Quarrystone armor units are known t
break into smaller pieces occasionally; but for the most part, structui
damage or failure due to stress fracturing of armor stones is not considéré
a major problem.
However, as coastal engineering advanced and coastal structures wei
planned for deeper water, hydraulic stability considerations dictated large
armor units, often surpassing the maximum stone sizes the quarry cou]
produce. In other situations, structures were proposed in locations whej
no suitable stone source existed. For these reasons coastal engineers turne
to the use of artificial concrete armor units of various sizes and ge<
metric configurations. Examples include dolosse6, Tribars, Tetrapods, A
cropodes, and solid cubes. Fracturing is not an important consideratic
for the bulky armor units such as the Accropodes and cubes where on
shape, surface texture, and the armor unit specific gravity are importai
similitude considerations (Owen and Briggs 1985).
The term dolos is singular, and the plural is formed as “dolosse”.
The problem with concrete armor units arose as slender armor uni
were made larger and larger, and several breakwaters suffered extensi'
damage that was attributed to breakage of the slender units. Where
these structures had been proven to be hydraulically stable in physic
model tests, armor unit breakage in the prototype resulted in smaller, h
draulically unstable, armor units that lacked the size and interlocking fe
tures of the intact units. The problem was compounded by smaller piec
impacting other intact units, causing them to fracture.
Coastal structure designers recognized the need to determine stress le
els in concrete armor units in addition to hydraulic stability; however, tl
stress problem is stochastic in nature because of the randomness in loadii
and contact supports (Burcharth, et al. 1991). This makes analytical ai
numerical techniques extremely difficult to implement.
As field experience accumulated, it became apparent that the larg
slender armor units had little tolerance for movement. This led to desi