Contents
xiii
7.2.1 General......................................................................... 211
7.2.2 Fluid mechanism of scour......................................... 212
7.2.3 Scour due to steady current................................... 213
7.2.4 Scour due to waves................................................... 214
7.2.5 Scour due to simultaneous action of waves
and current .................................................. 214
7.3 Sédiment Dynamics of Scour................................................ 215
7.4 Types of Scour.......................................................................... 215
7.4.1 General......................................................................... 215
7.4.2 General scour............................................................ 216
7.4.3 Local scour.................................................................. 216
7.4.4 Dégradation scour...................................................... 217
7.4.5 Boat scour.................................................................. 218
7.4.6 High-head scour......................................................... 218
7.4.7 Global or dishpan scour ......................................... 218
7.5 Scour Failures and Evolution................................................ 219
7.6 Scour Due to Vertical Walls ................................................ 220
7.7 Pipelines................................................................................... 222
7.7.1 General......................................................................... 222
7.7.2 Scour around pipelines............................................ 222
7.7.3 Scour around pipelines due to current action . . . 224
7.7.4 Scour due to waves................................................... 226
7.7.5 Scour due to waves and currents............................. 226
7.8 Maximum Scour Depth.......................................................... 227
7.9 Scour Protection....................................................................... 228
7.9.1 General......................................................................... 228
7.9.2 Rip rap rock fill......................................................... 229
7.9.3 Protective mattress................................................... 229
7.9.4 Buried toe.................................................................. 229
7.9.5 Sand bags or grout filled bags................................ 230
7.9.6 Concrète grout............................................................ 230
7.9.7 Structural improvements......................................... 230
7.10 Bed Shear Stress...................................................................... 230
7.10.1 Bed shear stress due to waves................................ 230
7.10.2 Current related bed shear stress............................. 231
7.10.3 Combined wave and current shear stress.............232
References............................................................................................ 233