FUNCTIONAL APPLICATIONS :
1.
Kotzebue
and
Ninilchik,
Alaska:
A. Tests involving gabion performance were conducted in Kotzebue and
Ninilchik, Alaska, in 1978 and 1979. At Kotzebue, gabions were deployed in a
198-ft- long revetment. T h e PVC coated gabions were lined with filter fabric
a n d filled with sand. Within a year, t h e gablons eventually deteriorated from
w a v e attack, debris, and ice forces. (US Army Corps of Engineers 1981)
B. At Ninilchik, Alaska, a tiered gabion groin was constructed to provide
t o e protection for a timber crib groin. The structure performed well
I n i t i a l l y , but later failed when the tier levels shifted because the gablons
w e r e not tied together. A gabion revetment was also constructed to provide
tow protection for a timber revetment, but waves with heights up to 6.5 f t
ripped the baskets apart, causing the loss of fill material, Damage may have
b e e n facilitated by wire corrosion due to the cracking of the PVC coating (US
Army Corps of Engineers 1981). B o t h gabion structures failed within a year.
c.
In both the Kotzebue and Ninilchik tests, the gabion manufacturer's
d e p l o y m e n t recommendations were not followed fully. The gabion fill material
should ideally range in size between 12 and 25 cm. (approx. 5 to 10 in.), but
s h o u l d certainly be larger than the mesh size to prevent the fill from
escaping, even when a basket liner is used. T h e gabions should also be tied
t o g e t h e r to provide structural strength and integrity.
D. B a s k e t liners should not be used. Although filter cloth was used as a
l i n e r in the previous applications to retain the fill material and reinforce
t h e gabions, It may have promoted structural Instability by diminishing
p e r m e a b i l i t y , thereby reducing the capacity of the gabions to absorb wave
energy.
Geneva State Park, Geneva, Ohio:
2.
A. A three tiered l00-ft-long breakwater with 4- t o 10-in. r o c k f i l l w a s
constructed at Geneva State Park, Geneva, O h i o , on Lake Erie in 1979. Filter
c l o t h was placed under two-thirds of the structure to ascertain settlement
differences.
S t r u c t u r e effectiveness was proven after a full tombolo was
created behind. and along the length of the structure. However, after a year
o f direct exposure to wave activity and debris, t h e gabion wire mesh failed.
N o significant differences In settlement with or without the filter cloth
underlayer had occurred by that time.
3.
Cape May Canal, New Jersey:
A. Cape May Canal, located at the mouth of Delaware Bay on the Atlantic
O c e a n , was the site of another gabion structure. Erosion by ship generated
waves necessitated some form of bank protection. In December 1982, 1500 ft of
galvanized and PVC coated gabion revetment was installed utilizing a stepped
s l o p e for increased wave energy dissipation. Gabion rock fill ranged in size
f r o m 10- to 20- cm. (approx. 4- t o 8-in.). A 10- to 13-cm. (approx. 4 to 5 in.)
t h i c k filter underlayer with crushed stone was also used.
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