Why must the foundations of gravity quay walls extend below the seabed?

To ensure the structural integrity and long-term performance of a gravity retaining wall, it is essential to extend its foundations below the seabed level for several critical reasons:

• Adequate Support: Extending the foundation ensures the wall has sufficient bearing capacity to prevent detrimental settlement.
• Lateral Stability: Gravity walls rely on their own mass combined with the passive resistance of the ground in front of them to remain stable against the forces they retain.
• Scour Prevention: Placing the foundation below the seabed protects the structure from the erosive effects of water movement, which can undermine the base of the wall.1

Modern engineering practice dictates that these depths are determined through exhaustive exploration of soil mechanics, including borings and laboratory testing, to mitigate the risks of soil instability.1