Wave-induced liquefaction in a silt and seashell mixture

This paper presents the results of an experimental investigation of wave-induced liquefaction in silt and seashell mixtures. Three kinds of sediments were used in the experiments: silt (d50=0.070 mm), coarse seashell (d50=2.87 mm), and fine seashell (d50=1.46 mm). With these sediments, three kinds of tests were carried out: silt-alone tests (the reference tests), tests with silt and coarse-seashell mixture, and tests with silt and fine-seashell mixture. The experiments showed that the influence of seashell content on wave-induced liquefaction is very significant. The susceptibility of silt to liquefaction is decreased with increasing seashell content. This is up to a certain point beyond which the mixture of silt and seashell becomes liquefaction resistant. For the seashells used in the experiments, this limiting value was found to be approximately SC≈30%, where SC is the shell content by weight. It is argued that this behavior is linked with the elastic modulus of the mixture. The present findings showed that the liquefaction criterion based on the initial mean normal effective stress in pure silt/sand can be extended to silt and seashell mixtures. A chart is proposed for an initial screening check of liquefaction potential. Furthermore, it is recommended that, if there is a liquefaction potential, standard assessment methodology may be implemented to check for liquefaction, provided that the elastic modulus and other properties of the soil and seashell mixture are incorporated into this assessment.