Protection of Pier Foundation of Zhongsha Bridge at Zhuoshui River, Changhua, Taiwan

Zhongsha Bridge, a 2,345m-long, traditional pre-stressed concrete structure, located on the Zhuoshui River in Central Taiwan between Changhua and Yunlin Counties. It had been the longest bridge in Taiwan when it was built in 1978. As the important link of north and south, the accomplishment of the bridge finalized the construction of the National Freeway No.1, the arterial which connects all the major cities on the west coast of Taiwan.

The river at the bridge has been facing continuous impact of fluvial processes. After its service of several decades, recently, because of long-term persistent severe scouring, some bridge pier foundations and their surrounding areas had shown extremely unstable and required an immediate remediation.
Considering the importance of the bridge, the design and construction of the remediation were strictly required to follow the highest level of engineering performances. The remediation consisted of riverbank revetment rehabilitation, repair and reinforcement of submerged-weir groundsill and aprons protection. The remediation was mainly to secure the bridge stability and ensure the necessary traffic safety. In addition, flooding always submerged the farmland adjacent to the river and put the residents and their property in great danger. The mitigation project also provided necessary protection for the farmland in that area against damage.

In this project, geotextile tubes, ACETube^® and geotextile mattresses, ACEFormer™ were adopted to solve the abovementioned problem. The protection was designed to be 5.6m high with four layers of ACETube^®. After each layer of ACETube^® was filled with in-situ sand, local fill was then placed and leveled on the top to make an even surface for the installation of the following layer. Such procedure was repeated until the four layers were finished.
At the end of construction, the four-layer structure was covered with ACEFormer™ filled with concrete, which not only increased the impact resistance of the structure and kept ACETube^® from external damages caused by driftwood or debris coming down the river, but also enhanced the stability of the pier foundations and levees. Furthermore, the mattresses used here were pervious which allowed the excess water in the structure to discharge into the river, thus making the structure more stable. The uneven surface of ACEFormer™ also helped reduce flow velocity and slowed down the erosion process.
ACETube^® and ACEFormer™ proved to be a better solution also because of their flexibility, which allowed them to easily adjust to various landforms in the process of construction. In this case, such property was especially advantageous when the construction was located at river curves. Both materials showed higher applicability than other rigid structures under such conditions.
As a result, the combination of these two materials provided more reliable protection to the pier foundations and the levees and essentially improved the structural safety of the bridge.

Both ACETube^® and ACEFormer™ are products of low energy consumption and low carbon emissions. In comparison with traditional concrete structural system, uses of ACE materials herein not only present eco-friendly sustainability, but also save the cost of expensive concrete material. In addition, the flexibility of these materials makes them adaptable to different kinds of landforms and site conditions, not only making construction much easier, but also helping the structures to accommodate to the environment. Even typhoons that bring disastrous floods were unable to cause any damage to them. The completed structures are beneficial for erosion prevention. The scouring of the pier foundations is now under control. The fertile newly-formed land even luxuriantly grows vegetation, making the site totally integrate into the surroundings.