Stiffness of subsoil

Stiffness is defined in terms of modulus of elasticity or shear modulus. As defined in elasticity theory, the modulus of elasticity links normal stress to strain (t= ex E) and the shear modulus links shear stress to shear strain (t= /xG). 

Many different elasticity moduli are referred to in Soil Mechanics  

In literature, 2 types of shear moduli are generally used G and Gg. Gg is the shear modulus at very small deformations (y 1 10 %). A correct definition of the shear modulus G should include the corresponding strain. 

In the literature, theoretical and empirical formulas exist expressing the relationship between several of these moduli (references). A clear definition of which modulus is meant when discussing stiffness moduli is therefore considered essential. 

Testing of the stiffness is in many cases linked to the above defined type of moduli  

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The stiffness of subsoil and fill material will define the deformation (or strain) to occur during and after construction of the reclamation. The deformation and consolidation behaviour of a reclamation must be estimated correctly for several reasons ... 

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