Experimental and Numerical Modelling of the Hydraulic Stability of Geotextile Sand Containers for Coastal Protection: Fid-Bau Portal

Experimental and Numerical Modelling of the Hydraulic Stability of Geotextile Sand Containers for Coastal Protection

Dassanayake Mudiyanselage, Darshana

More versatile materials and innovative solutions are required for the design of new, cost effective shore protection structures as well as for the reinforcement of existing threatened coastal barriers, including dune reinforcement and scour protection. Geotextile Sand Containers (GSC) is a relatively low cost, soft and reversible solution for the above problem with a history of more than 50 years in hydraulic and marine applications. Nevertheless, GSC is still an emerging technology and no proper guidelines are available for the design of GSC-structures on a sound scientific base. This PhD study attempts to evaluate the effect of the most important engineering properties of GSCs on the hydraulic stability of GSC-structures and to develop new formulae for the hydraulic stability of crest GSCs of submerged/low-crested GSC-structures. First, the present knowledge related to the engineering properties of GSCs and their effects on the stability of GSC-structures and the existing hydraulic stability formulae for GSC-structures were critically reviewed. Second, four series of especially designed laboratory experiments, which allowed us to have an insight into the influence of the above mentioned properties on the stability of GSC-structures and also to obtain the required parameters for the numerical modelling of their stability were performed. Experimental investigations consisted of two types of laboratory experiments (drop tests and pullout tests), small scale wave flume tests (hydraulic stability tests) and hydraulic flume tests (permeability tests). Third, numerical modelling of GSC-structures was conducted using the weakly coupled RANS-VOF model and FEM-DEM models. Finally, combining both the experimental and numerical results, new stability curves and simple formulae were developed for the hydraulic stability of crest GSCs. This newly developed stability curves and stability formulae are expected to foster the applications of GSC structures for coastal protection.