Restoration of No. 6 Groin with ACETube®, Gaoping River Weir, Taiwan

The Gaoping River supplies enormous amounts of water to Kaohsiung, accounting for about 70% of the city’s drinking water. However, during heavy rainfall in the Gaoping River Basin, significant erosion and scouring occur upstream of the Weir, leading to severe sediment accumulation downstream. The constant maintenance of the riverbank is crucial to ensure the stability and safety of the river.

This project is located approximately 3 kilometers upstream of the Gaoping River Weir. It is a concave bank that has suffered the most severe impact near the Weir. Consequently, the river bank has been significantly eroded, and the foundation of the groin nearby has also suffered extensive scouring.

The site conditions were applicable to use groin to divert or reduce the attack of the river flow acting on the concave riverbank. The existing groin was sitting on piles with many tetrapods around it. Although the groin was rigid, it could not prevent strong water currents from eroding the riverbed beneath its foundation.

ACETube^® geotextile tube is a monolithic-tubular container fabricated by multiple pieces of highly engineered synthetic woven fabrics. It is permeable yet efficiently retains soil particles within the container to form a flexible mass-gravity hydraulic structure suitable for waterfront or coastal protections. In addition, the structure size of ACETube^® can be easily adjusted according to site conditions and topographic changes. The designer thus applied ACETube^® around and below the groin structure. When the river flow encounters the ACETube^®, the permeable structure effectively absorbs the hydraulic energy and reduces the scouring force of the water. If some residual energy erodes the underlying soil, ACETube^® can flexibly intimate to the surface of the river bed as the terrain changes, thus mitigating the extent of the scouring.

The design of this case is unique because the groin has many closely spaced foundation piles. Challenges arose for solutions to accommodate these piles. Multiple vertical holes were preset in the body of ACETube^® to allow all the piles to pass through, ensuring complete erosion protection of the ACETube^®. The sand-filled flexible geotextile tubes can effectively wrap around the piles at the openings due to the tube’s inner pressure, minimizing erosion around the piles. ACETube^®, with groin structure, piles, and the surrounding tetrapods, become a successful well-integrated erosion protection system. This project confirms that the restoration with site-specific designed ACETube^® has successfully eliminated severe erosion and scouring of the targeted groin structure in Gaoping River.