poroelastic model

According to my understanding, there are two ways of prescribingporoelsticity in Abaqus.

One is to use poroelastic material model, and the other is by giving elasticmaterial properties in special states (instantaneous state and long timeequilibrium state).

You are using the first method, so you have to give logarithmic bulkmodulus, initial void ratio, shear modulus (or Possion's ratio). To answer yourquestion of where they come from, in Abaqus the elastic part of the volumetricbehavior of porous materials is
modeled accurately by assuming that the elastic part of the change in
volume of the material is proportional to the logarithm of the pressure
stress. To get the exact formular of bulk modulus in terms of average pressure,you can take a look at Abaqus ducumentation--> Abaqus user's manul-->materials-->elastic mechancialproperties-->poroselasticity-->elatic behavior of porous materials

 To use the second method, you have to give instantaneous Young'smodulus (instantaneous posson's ratio is assumed to be 1/2 automatically inAbaqus), and long time equilibrium Young's modulous  and long timePossion's ratio. You can not prescribe these properties directly in Abaqus CAE.You have to modify the in put file. There is an example in Abaqus exampleproblems Manual --> soils analysis