Unformatted text preview: conditions,
o Two different “slings” and quick release mechanism,
o Different toe details. Figure 6 – Simulated Crane Placement in Model and Actual Placement These test results confirmed the ability to place filter stone and armour units
during typical swell conditions (including achieving the required placement
density for the armour units), and also confirmed the stability of the resulting
structure under the design wave conditions. The tests also led to refinements in
the toe detail, and to the recommendation to use conservatively sized armour
units (to reduce down slope settlement of the armour layer). Regardless, the
ability to construct a suitable under layer in the field, and also to achieve good
placement of the armour units, remained a significant concern due to the
persistent swell wave conditions and the need for divers to verify placement
under dangerous conditions.
Although a study was planned to address the second issue noted above (i.e.
risk of armour unit breakage), this study was not completed, as the breakwater
design concept was switched from concrete armour units to a berm design when
a suitable source of quarried stone was confirmed.
Two berm concepts were considered, including:
• Single-class berm breakwater;
• Multi-class berm breakwater. 8 Baird developed the single class berm breakwater concept in the early
1980s, based on historical precedents and extensive physical model testing for
projects in Iceland and Alaska. The design concept is based on the use of a
wide, porous berm of armour stone to dissipate wave energy. This allows the
use of smaller armour stone than a conventional design, with better utilization of
the quarry, and provides an alternative to concrete armour units for exposed
locations, with the potential for significant cost savings. Baird’s most recent
application of this concept was for the rehabilitation of a damaged breakwater in
the Azores (refer to Scott et al, 2006), where a 30 m wide berm of 5 to 15 tonne
stone was utilized to resist a design breaking wave of Hs = 7.5 m.
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This note was uploaded on 02/04/2014 for the course HE 8450 taught by Professor Verhagen during the Spring '14 term at Technische Universiteit Delft.
- Spring '14