FluidSolidPorousMaterial

FluidSolidPorousMaterial couples the responses of two phases: fluid and solid. The fluid phase response is only volumetric and linear elastic. The solid phase can be any NDMaterial. This material is developed to simulate the response of saturated porous media under fully undrained condition.

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OUTPUT INTERFACE:

The following information may be extracted for this material at given integration point, using the OpenSees Element Recorder facility (McKenna and Fenves 2001): "stress", "strain", "tangent", or "pressure". The "pressure" option records excess pore pressure and excess pore pressure ratio at a given material integration point.

nDMaterial FluidSolidPorousMaterial $tag $nd $soilMatTag $combinedBulkModul <$pa=101>

$Tag	A positive integer uniquely identifying the element among all elements
$nd	Number of dimensions, 2 for plane-strain, and 3 for general 3D analysis.
$soilMatTag	The material number for the solid phase material (previously defined).
$combinBulkModul	Combined undrained bulk modulus Bc relating changes in pore pressure and volumetric strain, may be approximated by: Bc ≈ Bf /n where Bf is the bulk modulus of fluid phase (2.2x106 kPa (or 3.191x105 psi) for water), and n the initial porosity.
$pa	Optional atmospheric pressure for normalization (typically 101 kPa in SI units, or 14.65 psi in English units)

NOTE:

1. Buoyant unit weight (total unit weight - fluid unit weight) should be used in definition of the finite elements composed of a FluidSolidPorousMaterial.

2. During the application of gravity (elastic) load, the fluid phase does not contribute to the material response.