The influence of permeability on the erosion rate of fine-grained marine sediments

Abstract

Laboratory experiments have been carried out to investigate the erosion behaviour of a number of marine sediments which were reconstituted and sieved in various ways to ensure a large variation in soil properties such as (i) particle size distribution (including median grain size and fines content), (ii) bulk density, and (iii) hydraulic permeability. Based on the experimental results, it was found that for finer marine sediments the erosion rate at a given shear stress was sensitive to changes in these soil properties. No unique relationship was found between changes in the erosion rate and changes in the bulk density or fines content. More specifically, we find that the erosion rate at a given shear stress reduces with increases in density and fines content, but by an amount that is different for different sediments. In contrast, we show that there appears to be a unique relationship between permeability and erosion rate, such that permeability may be used to predict the erosion rate for the marine sediments at any density. By reinterpreting existing experimental results in the literature, we find that this same relationship between permeability and erosion rate is apparent for quartz sediments. We propose an empirical relationship, which fits well the erosion rate behaviour of finer sediments close to the threshold shear stress.