Modelling the equalizing process of rockfill dumps with a plough: Subsea cut and transport processes

Abstract

A way to equalize granular rockfill dumps at a sea or river bed is the use of a plough. A plough can be modeled as a set of straight blades in sequence. Several cutting models for dry and saturated sand are present in the literature. In cutting coarse material, the increase in pore water pressures caused by dilatancy of the grain structure play a minor role. This results in a different shape of the layer cut than for traditional cutting methods in fine soils. The layer cut has a limited surface slope resulting in grains rolling down under the angle of repose ?. Failure of the grain structure in coarse material depends mainly on the gravitational, shear and inertial forces between grains. This master thesis gives an analytical model for cutting rockfill larger than medium coarse sand with straight cutting blades (Chapter 4.2). A description is given of the important processes involved in equalizing with a plough and the different stages of filling. The analytical model is realized by use of models made by S.Miedema for cutting saturated sand and models for cutting dry sand by Hettiaratchi, and Reece (1966). The analytical model is verified by performing a physical scale model. The scale model is used to attempt to simulate the process in a discrete element computer model EDEM.