**Experimental Investigation of Local Scour Protection for Cylindrical Bridge Piers Using Anti-Scour Collars**

#### **Shunyi Wang, Kai Wei \*, Zhonghui Shen and Qiqi Xiang**

Department of Bridge Engineering, Southwest Jiaotong University, Chengdu 610031, China **\*** Correspondence: kaiwei@home.swjtu.edu.cn; Tel.: +86-182-0286-7260

Received: 18 June 2019; Accepted: 18 July 2019; Published: 21 July 2019

**Abstract:** Local scour of bridge piers is one of the main threats responsible for bridge damage. Adopting scour countermeasures to protect bridge foundations from scour has become an important issue for the design and maintenance of bridges located in erodible sediment beds. This paper focuses on the protective e ffect of one active countermeasure named an "anti-scour collar" on local scour around the commonly used cylindrical bridge pier. A cylindrical pier model was set up in a current flume. River sand with a median particle size of 0.324 mm was selected and used as the sediment in the basin. A live-bed scour experimental program was carried out to study the protective e ffect of an anti-scour collar by comparing the local scour at a cylindrical bridge pier model with and without collar. The e ffects of three design parameters including collar installation height, collar external diameter and collar protection range, on the scour depth and scour development were investigated parametrically. According to the experimental results, it can be concluded that: the application of an anti-scour collar alleviates the local scour at the pier e ffectively; and the protection e ffect decreases with an increase in the collar installation height, but increases with an increase in the collar external diameter and the protection range. Design suggestions for improving the scour protective e ffect of the anti-scour collar are summarized and of grea<sup>t</sup> practical guiding significance to the development of anti-scour collars for bridge piers.

**Keywords:** cylindrical pier; local scour; anti-scour collar; bridge; experiment; scour protection; scour development; optimal design
