CHENG KUNG ARTIFICIAL WATERWEEDS AS A PIER SCOUR COUNTERMEASURE IN A SUBMERGED OVERFALL

摘要

This paper proposed a new diversion method of directing the flow of water to decrease the pier scour, which was called Cheng Kung Artificial Waterweeds (CKAW). When the CKAW was installed, the velocity between CKAW and riverbed would decrease, so that the sand shielded by CKAW would move slower or even settle down, thus the pier scour was reduced. The pier can be kept stable and safe under the protection of the CKAW. This paper studied the protection of the pier scour by using CKAW in the submerged overfall. The pier was assumed to be located at the maximum depth area of overfall scour. Two factors of CKAW, length and cross-section's diameter, were chosen to study their protection effect. According to experimental results, the more efficient protection effect was achieved when the CKAW had smaller diameter, and was longer and close to pier's length. The maximum total protection effect could reach 46% to decrease scour in the experiments, in which the varied length had obvious effect on reducing the scour depth of overfall. When the length of the CKAW reached the pier, the protection effect was 78%. However, for the pure pier protection effect, the varied length had about the same effect, 20%. This showed the CKAW should be a good device for pier protection in the submerged overfall.