Particle size effects on the water retention properties of colluvial sediments

Abstract

This paper explores the influence of the particle size on the water retention properties of a colluvial deposit derived from banded iron formations in the Pilbara region in Western Australia. A small-scale experimental program aimed at evaluating the water retentions curve of four particle fractions (1.18 - 2.36 mm, 0.60 - 1.18 mm, 75- 600 μm and < 75 μm) is described. Water retention curves, defined in terms of the gravimetric water content vs total suction, were obtained by exposing the specimens to a controlled wetting path using the vapour transfer technique. Total suction was measured using a dew-point psycrometer. The experimental results show an important increase in the maximum water retention capacity with decreasing the particle size. Finally, the influence of the water storage of each particle fraction on the water retention curve of mixed specimens, i.e. those composed by several fractions, is discussed.