Anping harbor has been used for 36 years; the original design is now inadequate, so was required to build new facilities. In addition, dredging the harbor was also an urgent issue. The port authority required dredging the silt and using it effectively; otherwise removal of the silt would entail additional cost. To further land reclamation, the relevant dike engineering is anticipated to use the silt as construction material.
The Conventional Solution
The common structures of dikes are riprap or caisson. Riprap is expensive and less durable. Cast-in-place reinforced concrete caissons are durable but the cost is also high. While dredged silt can be used as filling material for caissons, it cannot be used for riprap structures. Therefore, finding a relatively simple and fast construction method at low cost, and which could take advantage of silt, is the biggest challenge of the case.
ACETube® geotextile tube is made of ACETex®, a product of polypropylene woven geotextile; when it is properly filled, it can be applied to build a dike. The required dike for land reclamation was 168m long and 10m wide at the bottom and 2.5m at the top. Considering in situ varying topographic contours, different sizes of ACETube® were designed. For this project, the tube circumference was 8.6m to 12.8m and the length was 37m to 47m. The total length of ACETube® used was 1,008m. It was then stacked up for three layers, to 5m high. The silt could fill the ACETube®, and backfilling the area behind ACETube® dike would provide the reclamation material.
In April, 2015, this dike was completed within one month. Besides the reclamation land, the dike constructed by ACETube® also used more than 5,200 cubic meters of silt dredged from the deposit area of the Harbor, effectively reducing the cost of silt removal. Comparing ACETube® and caisson, the ACETube® solution provides a relatively easy and faster installation and at a lower cost than using caisson. We can understand that the geotextile tube solution can be a good substitute to some traditional dike methods.