BREAKWATERS ON VERY SOFT SOILS. DESIGN, CONSTRUCTION AND GEOTECHNICAL MONITORING FOR FIUMICINO NEW SEAPORT

Rubble mound breakwaters are characterized by their considerable mass, as they generally consist of a quarry- run core, rock filter layer(s) and external armour layer made of rocks or concrete blocks. The weight (load) of the breakwaters is fully borne by the foundation ground. Since these structures are made at sea, foundation ground aligns with the seabed, which can be either natural or requires preliminary dredging. Consequently, the seabed and all subsoil layers experience a significant increase in tension. Depending on the nature and mechanical properties of subsoil, this could potentially lead to relevant geotechnical issues, ranging from lack of slope stability to large settlements. If thick layers of soft soil (e.g., normally consolidated clay) are present, critical settlement behaviour might be expected. Therefore, specific design solutions must be implemented. Due to the challenge of reducing the total amount of settlements, significant efforts are directed toward accelerating and concentrating settlements as much as possible during the construction phase.