Materials

This page outlines how to define soil and structural materials in STEM and highlights practical tips for choosing parameters.

Soil materials

Soil materials are defined by combining a soil formulation, a soil law, and a saturation law. Hereby an example of how to define two soil material layers. Further details about the soil formulation can be found in Linear elastic material.

from stem.soil_material import OnePhaseSoil, LinearElasticSoil, SoilMaterial, SaturatedBelowPhreaticLevelLaw

ndim = 3

soil_formulation_1 = OnePhaseSoil(ndim, IS_DRAINED=True, DENSITY_SOLID=2650, POROSITY=0.3)
material_1 = SoilMaterial(
    "soil_1",
    soil_formulation_1,
    LinearElasticSoil(YOUNG_MODULUS=30e6, POISSON_RATIO=0.2),
    SaturatedBelowPhreaticLevelLaw(),
)

soil_formulation_2 = OnePhaseSoil(ndim, IS_DRAINED=True, DENSITY_SOLID=2550, POROSITY=0.3)
material_2 = SoilMaterial(
    "soil_2",
    soil_formulation_2,
    LinearElasticSoil(YOUNG_MODULUS=30e6, POISSON_RATIO=0.2),
    SaturatedBelowPhreaticLevelLaw(),
)

Practical tips

Units: SI (N, m, kg, s, Pa).
Names: keep material names unique—used for mapping to physical groups and IO.
Drainage assumptions: In STEM for railway induced vibrations all the layers should be one-phase drained. This means that to simulate saturated layers the Poisson ratio should be set to 0.495. Please refer to formulation for further details.