Evaluation of Sand-Shell Mixture Behaviour for Breakwater Foundation

Abstract

The available sand material for a breakwater foundation is mixed with shells. The shell percentage of the sand material is variable and percentages up to even 50% are observed. It is essential to evaluate the properties and the behaviour of the sand-shell mixture as this will form the improved breakwater foundation. In reality the backfilled sand of the breakwater foundation has different relative densities in different depths. In this study the mechanical properties of the sand-shell mixture for different relative densities are evaluated. For different relative densities of sand-shell mixture the direct shear tests and the consolidated undrained triaxial tests are carried out on some samples. The results of the experiments showed that the samples with higher relative density show a higher internal friction angle. However, for the samples with even low relative density, an internal friction angle of less than 32° is not observed. The volume variation of the samples with different relative densities are monitored. Samples with low relative density showed a contraction behaviour; resulting in an increase of the pore water pressure, a reduction of the effective strength and finally the samples become susceptible to liquefaction. While the samples with high relative density showed a dilatancy behaviour.