Stability analysis for multilayered rubble bases

An analysis of the stability of multilayered rubble bases is conducted applying an approach that is based on numerical modeling. The approach consists of theoretical modeling of the interaction of water waves with a caisson-type breakwater and its rubble base and then employing the predicted flow field in a stability model to determine the required stone size. The flow in the rubble is described by the linearized Forchheimer equation of motion in a coarse granular medium. The boundary element method is applied to solve the problem of the interaction of water waves with the caisson and its rubble base, and to calculate the velocity field. The rubble base stability is determined as a function of the waves and the geometry of rubble base. It is shown that the stability increases with decreasing incident wave height, rubble base height, and bench width. Preliminary results also indicate the necessity of including permeability in the stability analysis. The theoretical results are in reasonable agreement with available experimental data.