Effects of Fines Content and Relative Density on Erosion and Recession of Predominantly Sandy Beach-Bluff System

Exploratory experiments including a series of flume and geotechnical tests were conducted to assess the effects of fines content and relative density on the erosion and recession of predominantly sandy beach and bluff. The beach and bluff were constructed using soils of four fines contents, 0, 5%, 10%, and 15%, at two relative densities of 39% and 68%, and were exposed to varying water levels and wave heights. The results indicated that the increase of fines content reduced the bluff recession rate. This reduction was more pronounced for looser soil, where a 5% fines content resulted in a nearly 24% reduction in the recession rate. The dominant failure mode for looser soils with 0% and 5% fines contents was shear failure. On the other hand, for the bluffs with fines content higher than 5%, as well as those with the denser soil, tensile failure occurred. The data resulted in the establishment of an empirical relationship for the recession rate as a function of fines content and relative density.