This section provides a brief summary of the moduli used to describe the compressibility of soil—elastic modulus, deformation modulus, and stiffness modulus—and shows the mathematical relationship between these values.
The moduli differ in terms of how they are determined, in particular through the implementation of the boundary condition for lateral expansion.
Modulus of elasticity E
- The modulus of elasticity is a material constant that can be obtained according to HOOKE from the uniaxial compression test (that is, with a uniaxial stress state). This allows for unrestricted lateral extension.
Stiffness modulus Es/Eoed
- The stiffness modulus depends, among other things, on the stress level and is obtained from the compression test (oedometer according to TERZAGHI). Lateral extension is prevented, resulting in a uniaxial stress state. It is also referred to as the oedometric modulus.
Deformation modulus Ev
- The deformation modulus depends, among other things, on the stress level and is obtained from the plate pressure test in situ. Lateral strain is only partially restrained.
The moduli mentioned can be converted into each other depending on the stress level if the Poisson's ratio ν is known. The following relationship arises, which can be found in the literature, such as [1].
In general, the following applies:
.