Articulated concrete mattress block size stability comparison in omni-directional current

Articulated Concrete Mattresses (ACMs) are scour protection method widely used for subsea pipeline protection and stability. In constructing ACMs more economical a stability analysis must be conducted for the required minimum weight estimate with safety factors. To date there are not theory accurate hydrodynamic coefficients for uses in determining stability analyses for full mattress. This research paper investigates the stability of ACMs through several experimental investigations into their hydrodynamic coefficients at all horizontal flow angles. The ACMs used for this investigation comprised of three block types the 300 series, the 500 series and the 400 series which has the bottom half of the 300 series but the top half of the 500 series. The main finding of the block comparison was that the 400 series in comparison to the 500 series has either 0.02m/s lower or 0.2 m/s failure flow rate higher depending on the failure criteria. This was also observed with the less favourable failure criteria for the 400 series. This implies no justifiably economic advantage for deployment of the 500 series over the 400 series to increased stability in high current flow.