Open AccessVelocity modification at the bridge abutments because scour
Author(s) -
Boriss Gjunsburgs,
Mārtiņš Vilnītis,
Jana Pařílková,
Mārīte Bižāne
Publication year - 2019
Publication title -
iop conference series. materials science and engineering
Language(s) - English
Resource type - Journals
eISSN - 1757-899X
pISSN - 1757-8981
DOI - 10.1088/1757-899x/660/1/012028
Subject(s) - critical ionization velocity , layering , flow velocity , geology , geotechnical engineering , flow (mathematics) , abutment , mechanics , shear velocity , supercritical flow , structural engineering , engineering , turbulence , physics , botany , biology
At the corner of the abutment were streamline concentration, sharp water level drop and rapid increase of velocity. Formula for calculation local velocity at the abutments is elaborated. Local velocity is depending on open flow parameters, backwater value, rate of contraction by bridge crossings and depth of scour. Relative local flow modification at the bridge abutment at plain river bed, relative local and critical velocities changes during scour at steady and unsteady flow, uniform bed and at bed layering is studied. Comparison of the local velocity with approach flow and mean velocity under the bridge opening was made. The local velocity V lt is reducing and the critical velocity V0t is increasing because of the scour within the time step at steady or at unsteady flow. When relative local velocity βV 0t /V lt becomes equal to one the scour stops. For unsteady flow local and critical velocities are different at any steps of hydrograph because of the increased flow discharge and the scour depth. Dependence of the relative local and critical velocities at steady and unsteady flow, development in time and because of the scour, impact layering of the river bed is presented in paper in Figures and compared with tests results.