20.7.6 Moisture swelling

Products: ABAQUS/Standard  ABAQUS/CAE  



Moisture swelling:

Moisture swelling model

The moisture swelling model assumes that the volumetric swelling of the porous medium's solid skeleton is a function of the saturation of the wetting liquid in partially saturated flow conditions. The porous medium is partially saturated when the pore liquid pressure, , is negative (see Effective stress principle for porous media, Section 2.8.1 of the ABAQUS Theory Manual).

The swelling behavior is assumed to be reversible. The logarithmic measure of swelling strain is calculated with reference to the initial saturation so that

where and are the volumetric swelling strains at the current and initial saturations. A typical curve is shown in Figure 20.7.6–1. The ratios , , and allow for anisotropic swelling as discussed below.

Figure 20.7.6–1 Typical volumetric moisture swelling versus saturation curve.

Defining volumetric swelling strain

Define the volumetric swelling strain, , as a tabular function of the wetting liquid saturation, s. The swelling strain must be defined for the range .

Input File Usage:           


Property module: material editor: OtherPore FluidMoisture Swelling

Defining initial saturation values

You can define the initial saturation values as initial conditions. If no initial saturation values are given, the default is fully saturated conditions (saturation of 1.0). For partial saturation the initial saturation and pore fluid pressure must be consistent, in the sense that the pore fluid pressure must lie within the absorption and exsorption values for the initial saturation value (see Permeability, Section 20.7.2). If this is not the case, ABAQUS/Standard will adjust the saturation value as needed to satisfy this requirement.

Input File Usage:           

ABAQUS/CAE Usage: Initial saturation values are not supported in ABAQUS/CAE.

Defining anisotropic swelling

Anisotropy can be included in moisture swelling behavior by defining the ratios , , and , such that two or more of the three ratios differ. If the ratios are not specified, ABAQUS/Standard assumes that the swelling is isotropic and that . The orientation of the moisture swelling strain directions depends on the user-specified local orientation (see Orientations, Section 2.2.5).

Input File Usage:           Use both of the following options:

The *RATIOS option should immediately follow the *MOISTURE SWELLING option.


Property module: material editor: OtherPore FluidMoisture Swelling: SuboptionsRatios


The moisture swelling model can be used only in elements that allow for pore pressure (see Choosing the appropriate element for an analysis type, Section 21.1.3).