Effect of armour unit layers and placement mode in the determination of stability of geotextile sand container (GSC) breakwaters

Geosynthetic Sand Containers (GSCs) are increasingly harnessed for their coastal protection capabilities. Recent studies point to its efficacy to be used even as armour units of breakwaters. The current investigation aims at understanding the effect of armour unit layers and placement modes in altering the stability of GSC breakwaters. Single-layered and double-layered GSC structures with slope parallel and perpendicular placement are tested for stability against wave conditions of the Mangaluru coast. A 1:30 scaled monochromatic wave flume model study is adopted to detail the damage levels and stability of various GSC breakwaters. It is observed that the stability of structure increased by up to 17% when supplemented with double layers. Structure tends to be stable with increasing armour units size and fill percentage. Larger bags stacked to double layers is found to be the most stable configuration. 80% filled, slope parallel placement exhibited the least stability. The paper dealt with all factors affecting structure stability and deduced stability nomograms helpful for coastal engineers to design GSC breakwaters. •A detailed review of performance of geotextile coastal protection measures has been carried out.•Paper serves as a design guideline for GSC structures, as there are very few published guidelines for GSCs.•Developed performance curves used for determining the extreme wave conditions where the structures can be constructed.•The effect of GSC size and sand fill ratio in the hydraulic performance of the structure has been identified.