Effect of Bridge Pier Shape on Scour Depth at Uniform Single Bridge Pier

Ghulam Murtaza,Naveed Ahmad,Daulat Khan,Usman Ali Naeem,Hashim Nisar Hashmi

doi:10.22581/muet1982.1803.08

Abstract

Bridge pier scouring may lead to the bridge failure and the shape of bridge pier itself is one of the main factor to control scouring around bridge pier. The amount of sediment which is removed from the boundary of bridge pier is called bridge pier scouring and the depth up to which sediment removed is called scour depth. Scouring results, the exposure of foundation, eventually leading to bridge failures. Assessment of the maximum scour that can be faced by pier has a vital role in the design of bridge foundation. Different techniques are used to minimize the scouring effect in order to control the bridge failure. In this study effect of bridge pier shape on scouring was checked on four different shape i.e. circular, oval, square and octagonal. Each pier shape was tested against three different values of flows i.e. 16, 22.50 and 29.50 liter/sec. Uniform bed material of standard deviation (g = 1.21) and median size (D50 = 0.28 mm) was used for all tests. Scour is measured with the help of point of gauge and bed is levelled before every experiment. Experimental results show that minimum scour is observed for octagonal bridge pier and maximum for square bridge pier while circular and oval faced intermediate scour depth relative to square and octagonal bridge pier. It is concluded that scour has reduced to 22% when octagonal pier was used compared to circular one.

Highlights

Bridge pier scouring may lead to the bridge failure and the shape of bridge pier itself is one of the main factor to control scouring around bridge pier
Raudkiviand Ettema [5] recognized that scouring process has three phases i.e. initial phase, principal phase and equilibrium phase.Scouring process is said to be in equilibrium phase when scour depth does not change with time.The concept of equilibrium scour is uncertain and different approaches has been adopted by different authors present to deal with it
Four piers of different shapes of equal width were used as pier model as shown in Fig. 3 since it was recommended by Chiew and Melville [13], that the pier diameter should be less than 10% of flume width in order to avoid the influence the walls which leads to contraction scour

Summary

INTRODUCTION

Recent studies show that the impact of flow originates the formation of horseshoe vortex and separation of flow from bridge pier leads to the rising vortex. These two are the main factors causing bridge scouring [4]. Lança [9] stated that the scour depth (d ) around uniform s single bridge piers depends on the depth of flow (d), median grain size (D ), pier width (D ), alignment and p shape of the pier, Width of channel(B) and time. Breusers [10] studied the effect of pier shape and alignment on local scour and reported that maximum scour is faced by rectangular pier. This study was related to check the impact of the uniform bridge pier shapes on local scour

EXPERIMENTALSETUP

RESULTS AND DISCUSSION

CONCLUSIONS