Breakwater Repair at Lajes
Air Force Base, Lajes, Azores
Description
Two-dimensional and three-dimensional physical model studies were conducted to study repair
scenarios for the breakwater at Lajes Air Force Base, Lajes, Azores. In addition, wave
transmission into the lee of the breakwater was measured for various breakwater repair scenarios.
The intent of the study was to determine the optimum breakwater repair plan.
The Azores islands are located in the mid-
Issue
Atlantic Ocean. Praia da Vitoria is a bay
located on the eastern coast of the island
of Terceira in the Azores. The harbor has
direct exposure to severe open Atlantic
storms from the east. A breakwater was
constructed in 1963 on the north side of
the bay entrance to provide safe refuge and
port for U.S. ships arriving at Lajes Air
Force Base. A wharf is located directly in
the lee of the breakwater, as shown on the
attached photograph. The breakwater was
originally armored with 15 t tetrapods. The
armor layer has sustained significant
damage during initial construction. Repairs to the structure were undertaken in 1963, 1964, 1966,
1970, 1973, 1985, 2002, and 2003. The structure continues to deteriorate. In 2001, the U.S. Air
Force employed the U.S. Navy to develop a permanent repair for the structure.
At the request of the U.S. Navy, two 1:56-scale physical hydraulic models were designed and
Products
constructed at the U.S. Army Engineer Research and Development Center by the Coastal and
Hydraulics Laboratory to study repair scenarios. One model of a breakwater section was built in
a 1.5-m wide by 61-m-long flume. A second model, a three-dimensional model of the breakwater
and bay covering a region roughly 2 km by 2 km, was constructed in a directional wave basin.
Modifications to the breakwaters were tested that include a CORE-LOC and antifer cube armor
Supporting Technology
layer with an optional fronting berm of mobile stone. The design CORE-LOC weight is 31.6 t.
The tested options were stable and the best option at study completion was a CORE-LOC-
armored superstructure down to the still water level and a fronting berm of stone. Construction of
this option began in late 2004.
This study developed a new composite structure type that is a combination of a low maintenance,
Benefits
very stable superstructure coupled with a relatively simple-to-construct underwater semi-mobile
rock mound. The composite structure is anticipated to be lower overall cost with much lower
construction-related complexity and risk and minimal maintenance over the life cycle. The physical
model study resulted in more than M of direct savings and considerable reduction in risk.
U.S. Air Force Base, Lajes, Azores, through U.S. Navy NAVFAC.
Sponsors
Dr. Jeffrey A. Melby, U.S. Army Engineer Research and Development Center,
Point of Contact
ATTN: CEERD-HN-H, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199;
e-mail: . Additional information can be found at
U.S. Air Force Base, Lajes, Azores; U.S. Navy NAVFAC, TranSystems Corp., Baird and
Partners
Associates.
U.S. Army Engineer Research and Development Center
August 2004
Coastal and Hydraulics Laboratory (Project/Mission Support)
www.erdc.usace.army.mil
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