Uses for Marine Mattresses in Coastal Engineering

Potential Uses

• In "Recent Advances in Geosynthetic Products Available for Coastal Engineering Projects," published in "Shore and Beach" magazine in 2001, E.J. Olsen outlines several geographic circumstances potentially favorable for marine mattress applications. The topographical conditions Olsen indicates as promising include coasts with irregular sub-grade surfaces on soft/weak soils; steep coastal slopes; coasts prone to wave reflection, wave run-up or breaking wave energy; saltwater environments; offshore areas requiring emergency repairs; and coasts where wave conditions impact the stability of an existing structure's perimeter.

Submerged Structure Protection

• Similar to a scour mat, marine mattresses placed at the base of submerged structure foundations, such as breakwaters and inlet jetties, prevent scour and deterioration. As significant scour may occur throughout construction of jetties, breakwaters and groins, placing marine mattresses before construction diminishes erosion and consequently decreases the amount of material required to stabilize the structure against strong currents.

Structural Reinforcement

• Constructing coastal structures near areas with poor soil strength becomes problematic, as submerged structures typically exert significant loads on foundation soils. To aid with this problem, marine mattresses distribute gravity loads over a larger area, because the geogrid basket reduces differential settlement where soil strength varies. Engineers anticipate in the planning process that marine mattresses will not eliminate differential settlement, however.

Submerged Pipeline Protection

• Marine mattresses protect underwater pipelines that have become unburied and exposed to currents and wave erosion. The porous nature of the mattress dissipates wave energy, and the massive weight of the mattress restricts movement of the pipe caused by currents and tidal pull.

Bank Protection

• Shorelines of rivers or protected bays, where wave exposure rates as low to moderate, can benefit from implementing erosion-control marine mattresses. Their geogrid layers tolerate greater wave action than comparable coastal retaining walls made of larger, loose rocks, and the densely packed stones protect sloping sand coasts from erosion by absorbing the energy of incoming water.