In an effective stress analysis, when multiple materials with different stiffness properties are used, it may be the case that the displacements at Stage 1 are not zero when viewed in Interpret. This is because the Modeler writes the appropriate initial stresses for the engine that generates zero displacement for the total stress option while for the case of the effective stress, resetting the displacement to zero is required.
To avoid getting upward displacements in the first stage, you can reset displacements after Stage 1 in the Modeler.
Reset All Displacements option in RS2 Modeler
Alternatively, you can specify a reference stage in the Stage Settings option in Interpret. The Stage Settings option in the Data menu allows you to set a Reference Stage>0 if you want to view differential data between any two stages of a multi-stage model.
Stage Settings dialog in RS2 Interpret