NUMERICAL AND LABORATORY EXPERIMENTS ON STABILITY OF GRANULAR FILTERS IN MARINE ENVIRONMENT

Geometrically closed filters are usually applied for marine structures, because they are designed neglecting the hydraulic load and geometrically open filters cannot be reliably designed so far. There are still gaps in the knowledge concerning hydro-geotechnical processes under the influence of oscillatory flow and combined oscillatory with unidirectional flow. The focus of this work is on the contact erosion at the interface between base and overlying filter under vertical oscillatory flow. Therefore, laboratory experiments on the stability of granular filters were performed. The objectives are (i) a better understanding of hydro-geotechnical processes, (ii) the description of hydraulic gradient, pore pressure and (iii) the development of prediction formulae for the hydraulic stability of granular filter under wave loads. Preliminary results show that geometrically closed filters are not stable under oscillatory flow and the hydraulic load cannot be neglected for a reliable filter design.