Geotextile Tubes as Submerged Breakwaters for Harbor Protection

With quick and prosperous development in years, the harbor in Taiwan has faced coastal erosion problems and requires an effective solution.

In 2014, the harbor authority found its south breakwater had shown serious foundation erosion, and the navigation channel also had been silting badly. The harbor authority was urged to solve these problems in consideration of low cost, construction feasibility, and environmental benefit.

Considering the wave flow variations and coastal structural conditions in this region, two sand fixation dykes with precast tetrapods and seven geotextile tube offshore submerged breakwaters are configured. The lengths of the sand fixation dykes at north and south side are 90 m and 350 m, respectively. The submerged breakwater consists of 7 sections of geotextile tubes with a dimension of 4m in height and about 1,160 m for total length. Each section is laid at a space of 60 m. The two sections on each side, with about 200 m in length apiece, connected to the sand fixation dyke and other five sections that are parallel to the coastline at about 100 m distance.

ACETube geotextile tubes, adopted as offshore submerged breakwaters in this project, allow the harbor authority to use silty materials dredged from the harbor area to backfill alongside the tube. In comparison with traditional breakwater with concrete or riprap, it can save more than 50% of construction cost. In addition, as the geotextile tube construction mainly uses the sand material on site and tubes are made of lightweight geotextile, the riprap exploitation and transport can be reduced greatly, also contributing to diminishing carbon emission from material production and transportation. By calculation, its carbon emission is only about 30% of that for traditional riprap breakwater.
Coastline protection is important not only to the safety of coastline inhabitants but also to the economic development of a country. With the awareness of sustainable development being aroused, using geotextile tubes in coastal engineering presents an alternative solution in considering energy saving and carbon reduction.