Initial settlements of rock fills on soft clay

Abstract

Rock fills that hit the seabed will remold the underlying material. If this material is a clay with sufficiently low shear strength, it will adopt rheological properties, causing flow through the rock fill, and contributing to the initial settlements of the rock fill in addition to conventional consolidation theory. The settlements of the rocks depend upon the height of the rock fill and how the rocks have been laid out. This is due to the viscosity of the clay, and the fact that clay is thixotropic. Thixotropy causes the viscosity to increase with decreased shear rate. The settlements finally come to a stop due to frictional forces from the surface area of the rocks. Clay is a non-newtonian Bingham fluid and will have a laminar flow through the rock fill. The Kozeny-Carman model is the most appropriate model for determining the permeability with laminar fluid flow through porous media. A clay with water content 52% and shear strength 0,35kPa had a viscosity in a viscometer of $eta$ = 7,8Pas. Comparing theoretical and experimental results for immediate and layered loading of the rock fill showed clay viscosities of 7Pas and 40Pas respectively.