Military bases along the Gulf of Mexican can be particularly vulnerable to storm surge flooding. To help protect Eglin Air Force Base, our marine engineering team designed three seawalls totaling 2,395 linear feet. While these seawalls help shelter three separate reaches of shoreline every day, they are designed and intended as protection for critical military facilities during storm surges.
The retaining walls consist of anchored steel sheet piles with reinforced concrete caps, which function as the wale for the bulkhead anchorage system, consisting primarily of steel tie rods anchored to a steel sheet pipe deadman wall. The tie-rods are housed within a PVC pipe to allow settlement of the subgrade materials without overstressing the tie-rod material. Due to the proximity of existing structures in certain areas of the sites, drilled post-tensioned earth anchors (tiebacks) were utilized instead of the sheet pile deadmen to minimize disruption to those existing structures. The steel sheet pile walls were designed for significant scour in front of the walls.
The wave attenuating rock revetments are situated directly behind the steel sheet pile walls and vary in height from 6 feet to 12 feet above the top of the concrete cap. The revetments consist of bedding material, riprap, and armor stone. The bedding material was placed on geotextile fabric on the existing subgrades and acts as the base layer for all other layers. The riprap is placed on top of the bedding and acts as a core for the revetment. The armor stone is placed on top of the riprap and resists the energy of the sea under design storm conditions. The armor stone varies in size with a maximum of 3.75 tons.
Seawall construction work also included temporary roads and facilities, site demolition, demolition of existing structures, backfill, grading, bedding stone, rip rap, armor stone, and paving.
This was a design-build project for the Army Corps of Engineers Mobile District with SKANSKA USA Civil, Southeast serving as Prime.