Problem description

When calculating in Classical mode in Plaxis the degree of saturation resulting from a groundwater flow analysis is not taken into account for the deformation analysis. In Classical mode Undrained A and Undrained B soils are assumed to be always fully saturated regardless of whether the soil is below or above the phreatic level. This implies that when loading the Undrained A or Undrained B type soil, excess pore pressures are always generated.

However, in PLAXIS 2D 2012 the Plaxis Output program shows for soils with Undrained A or Undrained B material behaviour a 100% degree of saturation (fully saturated soil) when the active pore pressures p_active < 0 and 0% degree of saturation (completely dry soil) when the active pore pressures p_active > 0. The latter is unfortunately incorrect as the degree of saturation for Undrained A and Undrained B soils is always taken as 100%.
Please note that the problem mentioned above only exists in the presentation of the results in Plaxis Output. The calculation itself has been performed using the correct degree of saturation, that is fully saturated soil.

For Undrained C materials both the active pore pressures and degree of saturation are undefined as an Undrained C material does not take soil and water separately into account. This is presented correctly in Plaxis Output.

Solution

This issue has been resolved in PLAXIS 2DAE.00