Physical laboratory tests are conducted to investigate the maximum inline force acting on seabed blocks under regular waves. The maximum shear forces determined from the logarithmic-law fit (based on wave-boundary-layer velocity measurements) are compared with the maximum inline forces directly measured by a strain-gauge-type load cell. It is found that the logarithmic-law fit results are about 40% to 60% smaller than the directly measured results under the conditions of a/ks, [0.1, 10]where a is the semiexcursion of fluid particles in the freestream, and ks is the equivalent seabed roughness. Based on the direct force measurements, a new correlation formula, together with a correlation between the seabed roughness and the spatial solidity, is proposed to estimate the inline force coefficient f , which forms the basis for predicting the inline wave force acting on seabed blocks.
Seabed blocks, such as geocontainers, artificial concrete mattresses, rip-raps, and the like, are commonly used for scour protection around subsea structures or as secondary stabilization measures for subsea cables/umbilicals. The estimation of the inline force acting on these seabed blocks is necessary for the in situ stability design of seabed blocks. This paper is concerned with the quantification of this inline force under wave conditions.