System of unit and creep law

FLAC3D
1

Hi have a question about the system of unit and how it interplay with creep.

In most creep constitutive model you have a least a parameter that is define in time. For example the prefactor in the power constitutive model.

To my understanding it will define the relation between the creep stepping and actual true time. Therefore, it might be convenient to define it in days or even years.

This is the case for one of the example in the documentation:
pressurized cavern which used a creep time-total in years.

Pressurized Cylindrical Cavern (FLAC3D) — Itasca Software 9.1 documentation

But if you have gravity in the model. gravity is always based on seconds (e.g. m/s2 or cm/s2, …). does that impact your creep model and you therefore you always have to have your creep constitutive model based on second or do you have flexibility?

Thank you in advance.

2

Gravity can alternatively be considered as the ratio of gravitational force to mass. As long as the mass unit is compatible with the force/stress unit—for example, in the SI system: kg/m³ with Pa, Mg/m³ with kPa, or Gg/m³ with MPa—it should be acceptable to use the same value of 9.81, as the stress unit will influence the units of the creep parameters.