Effect of matric suction on shear strength and coefficient of permeability on unsaturated soil

Abstract

     Many geotechnical problems are associated with unsaturated soils such as residual soils, expansive or collapsible soils, and compacted soils. Soil-water characteristic curve (SWCC) is central to unsaturated soil mechanics. The curve depicts water content versus soil suction relationship that governs the engineering behavior of unsaturated soils such as permeability, shear strength and volume change of the soils. SWCC can be determined using laboratory tests and several standardized laboratory test procedures are described in this paper. Having established the SWCC, the permeability, shear strength and volume change of soil can be estimated and used directly in performing geotechnical analyses. SWCC and permeability function are required in seepage analyses of water infiltration into unsaturated soils. The results of seepage analyses can be incorporated into slope stability analyses for assessment of factor of safety of a slope during rainfall. This paper also illustrates the use of SWCC in predicting of permeability function and shear strength of compacted soil for the Song Sat earth fill dam, Ninh Thuan province.