Mechanical excavation of clayey soils, a review of the physical phenomena occurring
Type:
Presented during:
CEDA Dredging Days 2024
Authors:
M.O. Winkelman, D.L. Schott and R.L.J. Helmons
Abstract
Clay is a notoriously challenging material to dredge. Due to its adhesion and plastic behaviour, it may clog the suction head of a dredge and clay balls could form down the pipeline. This will raise difficulties in estimating the production or the required power and increases the risk of downtime. As this is important for the dredging industry, there is a lot of literature on the cutting of clay in dredging, mostly it focused on the forces and stress distribution near the blade tip. Unfortunately, there is little information on the influence of adhesion and plasticity of clay on the deformation and the sliding of the clay chip over the tool and their contribution to the total cutting forces. Existing models on clay cutting are likely to miss some key details of clay behaviour. This paper, summarizes published results from experiments of cutting in clay. The results uniformly evaluated with dimensionless parameter groups derived by the Buckingham ? method. These ? groups can be used as characteristic numbers to investigate trends. The state of the art of models for cutting highly plastic materials is presented, providing a more detailed description of the excavation processes in submerged clay. The test results have been compared with the existing models. This provides insights regarding chip formation and the deformation of the chip as it moves along the tool. That knowledge provides a basis for solutions needed to avoid clogging of equipment and the occurrence of clay balls. In the next phase of the project, the identified ? groups will be used for the selection of the operational settings causing tear type cutting which leads to the break up of the chip into balls. This review is part of the CHiPS project, which investigates rapid large plastic deformations in submerged clay for Cutting Highly Plastic Soils.
Keywords: Clay cutting, Plasticity, Adhesion/cohesion ratio, Deformation types, Chip formation