Stress State Variable And Shear Strength Behaviour Of Unsaturated Soils

Abstract

Mechanical behaviour of an unsaturated soil is commonly viewed as being more complex and more difficult to be understood than that of a saturated soil. This is caused by the presence of pore air and pore water pressure together in the unsaturated soils model. Most of civil constructions are built over soils in unsaturated condition, in contras they are designed using saturated soil mechanics concept that is relatively different with unsaturated soil mechanics concept. This therefore can be understood because unsaturated soils have not been yet implemented in practical work. To produce more realistic solution for various soil mechanics problems, unsaturated soil mechanics have to be ready for application in standard engineering practice. It will require much more research to investigate mechanical behaviour of unsaturated soils that will provide subsequently confidence on the part of the practicing engineer. This paper concern to describe part of mechanical behaviour of unsaturated soils i.e. stress state variable and shear strength behaviour. Unlike saturated soils, two of three stress parameters σ - u a , σ - u w and u a - u w need to describe fully stress state of an unsaturated soil. The relationship between shear strength and suction are not consistent. There need an investigation to clarify this relationship and to develop an equation to calculate shear strength of unsaturated soils.