Dr., K..M. Hafez1 and Prof. Dr., A..M. Radwan2
1Aswan Fac. of Engng., South Valley Univ.
2Fac. of Eng. at Mataria, Helwan Univ.
In arid and semi-arid regions several types of soil are classified as unsaturated soils. Due to the
complexity of their meta-stable structure, their behavior commonly has been assessed
empirically. The relationship between water and air as the soil de-saturates is described by the
soil water characteristic curve (SWCC) which is the relation between volumetric water content
and soil suction. Hydraulic conductivity, shear strength, chemical diffusivity, water storage,
unfrozen volumetric water content, specific heat and thermal conductivity are all functions of
(SWCC). The most accurate way to determine (SWCC) is through laboratory experimentation.
Because of the high cost of laboratory equipment and the time required to run the test, alternate
methods are desirable. Statistical correlations between soil texture, soil water potential and
hydraulic conductivity can provide estimates sufficiently accurate for many analyses and
decisions. In this paper a comparison was done between the results of these alternative methods
for different soil types. A comparison was also done for a sandy clay soil using the results of a
laboratory test adopting the filter paper method. The paper also describes the effect of some
parameters affecting (SWCC) namely the percentage of organic matter, soil density and salinity.