
Field and Laboratory Suction- Soil Moisture Relationship of Unsaturated Residual Soils
Author(s) -
Bujang B. K. Huat,
Faisal Ali,
Abdul Adam Abdullah
Publication year - 2005
Publication title -
american journal of environmental sciences
Language(s) - English
Resource type - Journals
eISSN - 1558-3910
pISSN - 1553-345X
DOI - 10.3844/ajessp.2005.34.40
Subject(s) - soil water , water content , field capacity , soil science , permanent wilting point , consolidation (business) , suction , moisture , water retention curve , saturation (graph theory) , geotechnical engineering , degree of saturation , environmental science , pedotransfer function , geology , materials science , hydraulic conductivity , mathematics , composite material , mechanical engineering , accounting , engineering , combinatorics , business
Soils located above the groundwater table such as residual soils are generally unsaturated
and possess negative pore-water pressures. A soil-water (moisture) characteristic curve (SWCC) that
relates the water content of a soil to matric suction is an important relationship for the unsaturated soil
mechanics. The SWCC essentially shows the ability of an unsaturated soil to retain water under
various matric suctions. It has a similar role as the consolidation curve of a saturated soil that relates
void ratio or water content to effective stress. This study describes a study that has been carried in the
field and in the laboratory to examine the suction-soil moisture relationship of unsaturated residual
soils of granite and sedimentary rocks origin. The field measurement shows a decreasing trend of
suction with depth for both soils. The suction-soil moisture relationship shows two distinct curves, a
wetting (sorption) curve and a drying (desorption) curve. While from the laboratory study, it is
observed that there is a significant decrease in the soil moisture with increasing suction in the lower
suction ranges, until a de-saturation or air entry point for both soils. Beyond this point, the magnitude
of the decrease in soil moisture for the equal increment of applied suction is less. The de-saturation
point of a particular soil appears to be dependent on the amount of clay content. Higher amount of
fines in the soil constitute a more compact particle arrangement and a smaller pore size. Soils with
smaller pore sizes de-saturate at higher matric suction