Author(s): A. F. Negm; A. F. Ahmed; M. B. A. Saad
Linked Author(s): Usama Ijaz Farhat Ajaz Ahmed
Keywords: River Morphology; Navigation Problems; Dredging; Scour Holes; Riprap Protective Layers; Filter; Railway Bridge
Abstract: A decision was made to construct a railway bridge across the Nile River at Qena City about 288 Km downstream High Aswan Dam. Prior to the construction of the bridge a preliminary hydrographic field survey was conducted to assign the best location for the crossing. In order to facilitate the executional works, two groins were constructed on the two sides of the river. Accordingly, general deposition took place upstream the right side groin which caused the thalweg line to shift towards the left bank. Consequently, deep scour hole and severe bank erosion occurred at 60 m upstream the bridge near the left bank. The reflected flow current towards the bridge created another scour hole downstream the bridge pier No. 3 close to the left bank. To protect the bridge foundations, sheet pile coffer dams were constructed around each bridge pier which reduced the water area at the bridge site. Therefore, flow concentration near the left bank and high velocity threatened the safety of the bridge as well as the navigation within the reach. Several field investigations were conducted to assign the suitable solution as well as to evaluate the executed works. The solution included: 1) the removal of the two groins of volume 17, 700 m 3, 2) dredging a volume of about one milion m 3 of the deposited materials upstream and downstream the bridge, and 3) design protection layers of22, 442 m 3 volume for the generated local scour holes. The solution was considered to be successfully achieved when the results of the last general field survey revealed fair agreement with the bed condition before constructing the two groins. This paper presents a study case includes field investigations, data analysis and proposed solution and follow up activities which were carried out by the Hydraulics Research Institute (HRI) of the National Water Research Center (NWRC), Delta Barrage, Egypt.
Year: 1999