- مبلغ: ۸۶,۰۰۰ تومان
- مبلغ: ۹۱,۰۰۰ تومان
In this paper reduction of scour around group of two and three piers using circular collar has been carried out for the case of clear-water flow over uniform sediment. The efficiency of collars, with different sizes and spaces between piers is studied through experiments in group of two and three piers. The result reveals that collar has more influence in reduction of scour depth in rear piers than the first pier. Also, when the spacing between the piers increases the area without protection between the piers is washed away resulting deeper scour holes at the rear piers.
Recent scour-related bridge catastrophes through out the world have attributed general attention (Johnson and Dock 1996; Lagasse et al., 1995). The two major countermeasure techniques employed for preventing or minimizing local scour at bridge piers can be classified into two categories: (i) bedarmoring countermeasures and (ii) Flow-altering. In the former case, the objective is to combat the erosive action of the scour inducing mechanisms using hard engineering materials or physical barriers such as rock riprap. In the latter case, the objective is to either inhibit the formation of the scour inducing mechanisms or to cause the scour to be shifted away from the immediate vicinity of the pier. Chiew and Lim (2000), Lauchlan and Melville (2001), and Dey and Rajkumar (2007) focused on the first category and using armoring devices for reducing local scour at bridge piers. Efforts have been made to reduce scour by using submerged vanes (Odgaard and Wang, 1987), a delta-wing-like fin in front of the pier (Gupta and Gangadharaiah, 1992), and slot through the pier (Chiew, 1992; Kummar et al., 1999).
Collars are not only effective at reducing scour but are also much more economic when they are compared to countermeasure techniques like riprap. In this paper reduction of scour around group of two and three piers using circular collar has been carried out for the case of clear-water flow over uniform sediment.
Collars are effective on two and three piers in line, and reveal more efficiency when the space between piers completely covered with collars. The influence of collar in reduction of scour depth in rear piers is more remarkable than the first pier due to a weaker down flow at upstream face of the rear piers.
Using collar caused the delay in scouring mechanism and by increasing the size of collar the delay time was increased as well. As the spacing between the piers increases, the area without protection between the piers is washed away resulting deeper scour holes at the rear piers.