Page 238 - Materials Chemistry, Second Edition

Ch006-P373623.qxd 3/22/07 5:36 PM Page 217
6.6 Breakwater Recycling of Municipal Solid Waste Rejects 217
Water waves are one of the main problems facing coastal zones and shore
protection. Reinforced concrete blocks and stones are always used as a break-
water to protect the shores and coastal zones. They cost a lot of money and
should be replaced frequently depending on wave velocity and wave height.
HDPE is being used to manufacture breakwater structures especially float-
ing breakwaters (Whisperwave, 2005). Such technological advancement has
been utilized to afford protection to marinas, beaches, and private property
subject to destructive or annoying wave/wake forces. The design of the mod-
ule enables it to be filled with or evacuated of water (with the help of a stan-
dard air compressor) to precisely adjust its buoyancy. The module can be
“puncture proofed” by filling it with marine grade buoyant foam.
Accordingly, the most favorable scenario would be producing a shore-
line erosion protection structure using plastic recycled material. As men-
tioned earlier, the main aim is utilizing solid waste rejects in producing
shoreline erosion structures, preferably floating. The alternative material is
made out of rejects mixed with sand to produce breakwater or floating break-
water by adjusting the percentage of sand without sacrificing the properties.
The high percentage of plastics is always recommended to increase the life-
time of the sand-plast breakwater. The use of rejects in breakwater products
might require further analysis for leachate to make sure there is no water
contamination.
Breakwaters are generally shore-parallel structures that reduce the amount
of wave energy reaching a protected area. Breakwaters are built to reduce wave
action through a combination of reflection and dissipation of incoming wave
energy. When used for harbors, breakwaters are constructed to create suffi-
ciently calm waters for safe mooring and loading operations, handling of ships,
and protection of harbor facilities. Breakwaters are also built to improve maneu-
vering conditions at harbor entrances and to help regulate sedimentation by
directing currents and by creating areas with differing levels of wave distur-
bance. Protection of water intakes for power stations and protection of coast-
lines and beaches against tsunami waves are other applications of breakwaters
(Burcharth and Hughes, 2003).
When used for shore protection, breakwaters are built in near-shore
waters and usually oriented parallel to the shore like detached breakwaters.
The layout of breakwaters used to protect harbors is determined by the size
and shape of the area to be protected as well as by the prevailing directions
of storm waves, net direction of currents and littoral drift, and the maneu-
verability of the vessels using the harbor. The cost of breakwaters increases
dramatically with water depth and wave climate severity. Also poor founda-
tion conditions significantly increase costs. These three environmental fac-
tors heavily influence the design and positioning of the breakwaters and the
harbor layout (USNA, 2006).