ENGINEERING RESILIENCE
Unlike quarried armor stone, Accropode TM units are designed with an irregular shape that allows the individ- ual units to interlock with one another. Rather than func- tioning as individual blocks, the units form an interlocked armor layer capable of resisting much more severe wave con- ditions than armor stone. The units are placed as a single layer, in a controlled manner (i.e., on a specified placement grid with controlled orientations) over a prepared underlayer comprised of quarried stone. An important feature of the Glass Breakwater repair pro- ject is the decision to reuse the existing stone materials to create the underlayer rather than importing new stone. The existing armor stone, which ranges in size from approxi- mately 2 to 30 tons, will be reshaped to provide the under- layer for the Accropode TM layer. Treflik-Body explained that under Guam’s severe wave conditions, simply replenishing armor stone would leave the structure vulnerable to future storm damage and deg- radation, with the potential for localized failures/breaches through the structure. The interlocking and mass of the Accropode TM units provide a more resilient long-term solu- tion with a significant increase in stability and resilience to future storms and climate change. Putting the design to the test Before construction began, Baird subjected the proposed design to extensive physical modelling at the National Research Council’s Ocean, Coastal and River Engineering Research Centre in Ottawa, Canada (NRC). Both two- dimensional and three-dimensional physical models were constructed at a scale of 1:50. The testing program examined Accropode TM stability, the performance of the stone underlayer (comprised of existing stone materials), the mobility/stability of the relic debris field upon which the repair design is founded, the depth required for the excavated toe trench, and the risk of damage to partially completed works due to storms that occur during construction. The NRC team recreated Guam’s distinctive bathymetry, including the steep offshore shelf and the roughness associ- ated with the coral reef environment. The existing break- water profile, armor stone and relic debris field were also replicated. Even the placement of the model Accropode TM units followed the same orientation and installation prin- ciples that are used for installation in the field. The team conducted testing well beyond normal design conditions. The program included repetitive storm testing, including the impact of multiple storm events occurring in sequence without intervening repair works. The model testing also examined partial construction. Working benches and partially completed sections were
Courtesy of W.F. Baird
Highlighting the size of Accropodes TM .
Courtesy of W.F. Baird
A three-dimensional physical model at a scale of 1:50.
exposed to storm conditions to assess the risk of damage to partially completed works during construction. The testing ultimately demonstrated that the selected repair design, consisting of an Accropode TM armor layer founded in an excavated toe trench, could withstand the project’s design wave conditions as well as significantly more severe “overload” conditions. Construction underway The repair project moved into construction in late 2025, beginning with contractor mobilization and the casting of Accropode TM units. A 300-foot test section had been com- pleted and more than 1,000 units had been cast at the time of Treflik-Body’s presentation in Guam. Construction follows four primary stages. First, crews excavate and create a working platform that allows equip- ment to reach the relic debris field. The toe trench is then excavated into the relic debris field, establishing the
October 2026 — PACIFIC PORTS — 41
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