An Equation Describing the Shear Modulus of Unsaturated Soil

The small-strain shear modulus of unsaturated soils is a valuable tool for use in engineering practice, given that most soils remain unsaturated throughout the operational lifetime of the earth structure. Shear modulus is a key parameter required in the response behavior of geotechnical earth structures. Since the measurement of shear modulus for unsaturated soils is extremely time consuming and requires elaborate and expensive testing equipment, it would be beneficial to practicing engineers to have empirical or semi-empirical methods for estimating the small-strain shear modulus for unsaturated soils. This paper presents a method to describe the shear modulus behavior with respect to the stress state variables of matric suction and net mean stress. This method uses a relationship that allows for the potential of a priori generation of shear moduli for unsaturated soils. The relationship was developed for monotonic loading of remolded normally consolidated soils, without stress history hysteresis effects. The shear modulus relationship was further developed using multiple linear regression analyses to correlate the soil material constants to soil index properties that are representatives of the soil structure and material constitution.