Padma Multipurpose Bridge Project

22. Typical cross-sections layout (Type 6 for north bank and Type 2 for south bank) are provided inFigure 2-6 and Figure 2-7, respectively.Low water level 1.2m PWDFigure 2-6: North Bank Type 6 (Geobags) Cross Section2.3.2.4 Details of Wave Protection – Berm and Upper Slope23. Wave protection covers the berm and slope from below low water level either to the floodplain orto the top of embankment, a zone where wave action is the governing hydraulic design condition. Inaddition, the surface is designed sufficiently robust to cope with daily wear-and-tear of people andequipment accessing the water, and to consist of low-value elements. Concrete blocks meet theserequirements and have a demonstrated history of successful use in Bangladesh. The wave protectioncomprises several elements as described below:Berm24. The wave protection layer starts at the outer end of the berm below low water. The top surface ofthe berm is set at El. -1 m PWD and consists of two layers of loosely dumped concrete cubes of 30 cmsize (65 kg weight, 0.6 m³ of concrete per m², average layer thickness after dumping 95 cm at 35%void ratio).25. The berm is on average 5 m wide and fulfills the following functions: (i) by varying its widthsomewhat, the natural bankline can be adjusted to form more of a straight line above water, (ii) itincreases the geotechnical stability, and (iii) it allows country boats and light vessels to approach thebank but discourages the berthing of larger ships.Slope from berm to low water level26. The slope from the inner edge of the berm up to El. 2 m PWD (slightly above low water level) iscovered with loosely dumped concrete cubes - as described above for the berm.2-12