Modeling the effect of water depth on rock cutting processes with the use of discrete element method
CEDA Dredging Days 2015 - Innovative Dredging Solutions for Ports, Rotterdam
Helmons RLJ, Miedema SA and van Rhee C - Delft University of Technology, the Netherlands
Abstract: Whether it is for the construction of ports on new locations, the widening of canals through mountainous terrain or deep sea mining, efficient rock cutting is still one of the challenges that the dredging industry is facing. This gets more challenging by the fact that in dredging rock cutting is most of the time an underwater process. The water that is surrounding the rock and in the pores of the rock can have a major influence on the rock cutting process by increasing the required cutting forces.
During cutting, the rock matrix deforms and as a result local fluid pressure differences will occur. The magnitude of these pressure differences, and thus its effect on the cutting process, depends on the water depth and the cutting velocity. As a result of this, rock that is brittle under atmospheric conditions will behave more ductile in larger water depths. This paper focuses on the effect that the water depth can have on the cutting process.
The Discrete Element Method (DEM) has been successful in the modeling of rock cutting processes for dry, land-based operations. In order to make the DEM useful for underwater excavations, it has been extended with a fluid coupling. Results of this extension with respect to the effect of water depth will be presented. A clear distinction between shallow water (brittle) and deep water cutting (ductile) is observed. The newly developed method will give more insight in the physical processes that occur during cutting and it can help to improve the design and operational guidelines of the cutting equipment and processes.
Key words: rock mechanics, rock cutting