**6. Small-strain shear modulus based on bender element measurement**

According to elastic theory using the measured S-wave velocity (Vs) and total mass density of the specimen (ρ = γ/g), the small-strain shear modulus (Go) can be calculated with the relationship Go=ρ·Vs 2. Go is an important and fundamental geomaterial property for a variety of geotechnical design applications and can be applied to all kinds of static (monotonic) and dynamic geotechnical problems at small strains (Richart et al. 1970, Jardine et al. 1986, Burland 1989). Note that the term "small-strain" is typically associated with the shear strain range below the elastic threshold strain (10=3-10-2%). Within the small strain range where the deformations or strains are purely elastic and fully recoverable, the shear modulus is independent of strain amplitude and reaches a nearly constant limiting value of the maximum shear modulus. In this strain region, most geomaterials exhibit linear-elastic behavior.

A number of factors affecting Go have been extensively investigated and reported. These include the current state of the sample (e.g. stress state, overconsolidation ratio, density, void ratio, and microstructure), anisotropy, degree of saturation, aging, cementation, and temperature. Such factors can be briefly explained as the followings:
