ACE Geosynthetics Inc. Taichung City,
Producer: ACE Geosynthetics Inc.
Supplier: ACE Geosynthetics Inc.
Please describe the project specifications
The project is located near Taichung harbor in central Taiwan. Due to the coastal structure is often subjected to the momentary impact of the wave strength, the seawall of embankment is gradually eroded and the buildings as well as facilities which are constructed near the area are often partially destroyed by affecting the normal life of people. In order prevent this event from happening in the future, it has been adopted a cost-effective solution which takes into account both sustainable development of the environment and overall safety. The solution is about applying geotextile tube as remediation that offers many features such a rapid and local construction, minimizing carbon footprint, environment friendly and low-cost characteristics. The installation of geotextile tubes with 4m height and 15m width is totally divided into seven sections. Additionally, the total length of the submerged breakwater is around 1,160 linear meters.
What was the purpose of this project? What did the client request?
There are two main problems which need to be straightening out urgently. The first issue is in regards to the high difference of sea wave tidal ranges in the breakwater of Taichung Harbor. Although there is a concrete seawall, but due to the big impact of the waves, the foundation of the breakwater had been eroding for years. In addition, the second problem is the sand is moved by the current towards the area outside of estuary and then it is accumulated resulting in sediment deposition in the surrounding breakwater of the harbor. So the sand needs to be dredged but wants to be reused.
Nevertheless, Taiwan's traditional coastal protection methods are generally made of a large amount of construction with concrete. In other words, the costs for these traditional solutions are extremely high and the appearance of the structures is not ecological at all. After cooperating and discussing with project owners, it is decided to adopt geotextile tubes in order to minimize project budget, but at the same time deliver both construction feasibilities and environmental benefits.
What is unique or complex about the project?
A mean tidal range is as much as about 4.0m. Considering the wave flow variations and coastal structural conditions in this region, two sand fixation dykes with precast concrete armour units and seven temporary geotextile tube offshore submerged breakwaters are configured. The lengths of the sand fixation dykes at north and south side are 90m and 350m, respectively. The total length of the temporary geotextile tube offshore submerged breakwater is about 1,160m. The adopted geotextile tube has a single circumference size of 34m, the length is 33.75m, and it could also be considered the rare circumferences applied in the marine/hydraulic applications using geotextile tubes. The tensile strength of the geotextile used for the geotextile tube production is made by polypropylene material and 200kN/m x 200kN/m, the submerged filling of the geotextile tube reaches up to 4m height. Besides the fact that huge shape structures increase the challenges for installation, there is another difficulty which is the filling in submerged conditions. The tidal range of the job is up to 4m, the apparent wave height is about 2.1m, and the maximum depth of water is nearly 8~10m. Also, because the geotextile tube has flexible structure, it causes inconvenience during the construction. For instance, the geotextile tubes can roll or be away from the alignment position and the work is usually interrupted by the impact of the waves. Therefore, the whole process of the job should be controlled carefully. A rail with fixed pile is applied with aim to help the filling job with the pumping sand and divers.
What were the results of the project?
In fact, the geotextile tube plays a very successful role in this project. Not only it dissipates the wave energy in advance but also in combination with the water pump at rear, the sand is accumulated in the coastal line to nourish the beach. As consequence, the impact of long wave can not affect the embankment directly and can efficiently prevent the erosion problem. As the design of the program can greatly reduce the amount of purchased rubble and reuse the existing sand, the project costs only half of the general design program expenses. The method of geotextile tube has a very superior economy comparing to the traditional proposal.
Furthermore, the option of geotextile tube as offshore embankment mainly uses in-situ sand and geotextile tubes produced with light-weight geotextiles. This is also the reason why can reduce the material transportation costs and the acquisition of rubble or wave blocks. In the project life cycle, the process of materials and transport is efficiently reduced.
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