"UNSuitable" TO "suitable", a change in the reclamation design paradigm
Type:
Presented during:
CEDA Dredging Days 2024
Authors:
C. Hoffmann and F. Hompes
Abstract
The term "suitable" soil within the dredging environment is associated to soil materials (in general granular soils with a limited amount of fines) which during its placement produces a minimum segregation and settles within reasonable engineering times (almost immediately). After its emplacement, reclamation fill of "suitable" soil has enough bearing capacity allowing the access of typical construction machinery, either for the soil improvement works (if needed) or to continue further with the construction of the required facilities. The availability of "suitable" sand has become a limiting factor in the development of many ambitious reclamation projects making the re-use of existing, less suitable, materials a critical solution. This subject has been given broader international attention in the past years driven by the shortage of sand resources and by the desire for a more circular society where waste does not exist. So far, only a few examples exist of (nature) islands that have been constructed with fine silty or even clayey sediment. In this context, the reclamation with sediments must evolve from an exceptional case requiring special considerations, to become "common practice". Facilitating this change requires the review of several design paradigms and turning the design process around: instead of imposing specifications for a reclamation, the starting point should be the source material. What type of sediment is available? What needs to be done in the reclamation to turn this into land fit for purpose? The answers to these questions will directly influence the time required to finish a project, the (most suitable) work method, the equipment to be employed, and the (most suitable) form of contract. In this new scenario a significant transfer of time and costs from the dredging operation to the reclamation site is to be expected.
Keywords: Suitable-unsuitable soils, Composite soils, Reclamation design, Bulking factors