Characterizing the deformation of lumpy fills
Type:
Presented during:
CEDA Dredging Days 2026
Authors:
J. Snijders Blok, L. van Paassen, M. Cabrera and R. Helmons
Abstract
The dredging industry is evolving to meet new challenges, including sustainability demands and declining sand availability. A key focus is improving methods to use locally available soils and to make them suitable for reclamation. When stiff cohesive soils are dredged, they often form large lumps or balls during transportation, which are subsequently deposited within a reclamation fill alongside a slurry. These lumps form a matrix with inter-lump voids, resulting in a double porosity system that complicates settlement predictions. Current settlement calculation methods assume uniform layers and use generalized soil parameters, which are later adjusted with field data. This introduces significant uncertainty, increasing both risk and cost. In this study, we investigate the deformation behavior of stiff, lumpy double porosity fills by performing controlled experimental research. An experimental campaign involving oedometer testing and micro-CT scanning was conducted on clay lumps of varying undrained shear strengths to quantify deformation of macro- and micro-voids, and softening effects. Findings from this work reveal that traditional 1D-consolidation models, based on homogeneous assumptions, underestimate settlement magnitudes and their rate during early loading phases due to the collapse of the macro-voids. After macro-void closure has taken place, the fill behaves more like a homogeneous clay, but remains structurally heterogeneous. It is concluded that accurate settlement prediction for lumpy fills must account for the transition from macro-voids collapse to micro-voids consolidation.