Erosion control blocks (page 9)

Feasibility Study (abr.) into the Hydraulic Applications of Terraforce "G" 150 & "HD" blocks (cont.)

PROTECTION AGAINST WAVE ACTION

Concrete block armour has been used successfully in bank protection subject to wave action. The significant wave height of the area would dictate the suitability of the Terraforce "G" and "HD" blocks for similar use. Considering the weight of the Terraforce blocks, typical applications would be in lagoons, marinas, the upstream sides of earth embankments and river banks subject to boat-generated waves. Maximum Wave Heights for Terraforce Blocks

Assuming a Hudson stability factor of the Terraforce "G" 150 Blocks of 15 (CERC, 1984), maximum significant wave heights were calculated for the two types of Terraforce blocks.

These maximum significant wave heights are relatively large for inland waterways and could be generated over a fairly long fetch or by large and/or high-speed vessels. Thus, for the average river bank or lagoon, waves would not present too much of a structural problem, although due to the cyclic loading of wave action, some kind of filter is essential to prevent erosion of the subsoil. The filter may also have to be protected against damage due to wave action.

Filter Layer Design

Wave action on a revetment causes some of the highest forces on the subsoil below the armour layer, making a well-designed filter layer essential to the stability of the structure. In particular the filter should prevent migration of the soil particles through the concrete block armour whilst still being porous enough to prevent a high pressure build-up within the subsoil.