ABSTRACT
Nearly 50% of embankment dam stability problems are due to internal instability of the soil of homogeneous dams, or dam filters in the case of engineered dams. This instability can manifest as seepage induced internal erosion of fine particles through the coarser soil matrix. This study discusses the design of a new triaxial permeameter capable of investigating the influence of seepage on internal erosion of a model soil under controlled stress conditions. Two triaxial tests are reported here, using model soil of a specific gap graded particle size distribution, prepared to the same initial conditions of density and stress. The first test was conducted as a control, to examine the strength and stiffness under non-eroded conditions. In the second test, downward seepage was applied to the sample prior to testing in order to erode fine particles from the matrix. The gap-graded model soil samples were used in two distinguishable colours (corresponding to coarse and fine) to ensure that the eroded particles seen were from the original fines content and not a product of crushing in the coarse matrix.
