A dynamic calculation will use more RAM than a static (Plastic) analysis of the same model due to the additional mass matrix and damping matrix. This additional memory usage depends on e.g. the materials used, the element size, and the boundary conditions.

As a rough rule of thumb, the estimated memory usage normalized to a static Plastic calculation of the same model:

• Plastic calculation: 100%
• Dynamic calculation with viscous boundaries: can use up to 200% memory
• Dynamic calculation with free field boundaries and a compliant base bottom can use up to 400% compared to the Plastic calculation of the same model
• Using user-defined soil models can also increase memory usage. By using e.g. the PM4 Sand soil model to model liquefaction behaviour, the memory usage can use up to 200% compared to the static Plastic calculation

When combining free field boundaries/compliant base bottom with PM4 Sand (user-defined soil model), the memory usage can go up to 800% compared to the static Plaxis calculation.