Erosion control blocks (page 6)

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

PROTECTION AGAINST STEADY FLOW

Steady flow refers to flow in estuaries, rivers, canals and over dam spillways where there is a fairly steady flow of water. In many cases such flow occurs through alluvial soil conditions, with consequent dangers of erosion. To prevent this erosion of the bed and banks of these structures, it is necessary to protect them with some form of lining such as concrete elements. Two main aspects have been dealt with, namely block layer stability due to direct flow forces and stability related to the foundation on which the blocks are placed.

MAXIMUM FLOW VELOCITIES FOR TERRAFORCE BLOCKS

Based on the theoretical considerations, the following critical allowable flow velocities have been calculated for varying flow depths - click here to view the table.

It can be seen from this table that the Terraforce blocks can withstand relatively high flow velocities. This means that the potential for erosion will also be high, especially since the Terraforce blocks have a high porosity. To prevent erosion of the subsoil, some form of filter will have to be provided underneath or behind the blocks. It would therefore appear from these theoretical considerations that as long as precautions are taken to prevent the erosion of the subsoil, both the Terraforce "G" and the Terraforce "HD" blocks would be suitable for steady flow protection systems if the maximum allowable velocity given is not exceeded.