STUDY OF LOCAL SCOUR AROUND BRIDGE PIERS

Abstract

Scour around bridge is considered one of the sever problems facing hydraulic engineers. It is considered one of the most critical problems in bridge pier design because of dynamic nature of scouring. Neither the worst case nor the net effect can be easily predicted, where such design requires an estimation of max. scour depth at the pier during construction of a bridge.

This thesis studies the scour depth around circular pier at IMBABA bridge as one of the important bridges Cross River Nile in Cairo-Egypt. Also to study the long-term scour upstream the bridge at circular pier. A field data \vere measured in [ 199.2]. which contains 29 measured cross-sections including measured Yelocity at three cross-sections U. S. and D. S. And twel\"e samples of bed material \vcre taken to construct a mobile bed model. Recent field data had been measured in r I 996 J. \Vhich contain I 9 cross-sections upstream and

downstream the bridge. An experimental study usmg an undistorted Model, clear-water scour condition \\ ith sand;· bed has median diameter d 50 =0.268mm conducted in Hydraulic Research Institute (HRI), Ministry of Water Resources and Irrigation (MWRI). T\velve runs were conducted including three different Yalue of tlmY depth (Y). The experimental results were used to investigate fiye empirical formulae for estimating maximum scour depth at circular pier as a function of discharge, velocity. Froude number, densimetric Froude number and normalised velocity. Also experimental results compared with common formulae (Colorado State University (CSU) and Froehlich formulas). The measured cross sections in 1992 and 1996 were used to compare bed level .It was found that no significant change in the bed level. Hopefully, this thesis makes a contribution to the problem of estimating the local scour depth around bridge piers.