Soil Modeling

Hi

Please help in modeling the soil.

I  modelled soil as non linear springs in Abaqus?Standarads and analysed the pipe behavior for hydrodynamic loading.

I am currently planned to model the pipe-soil interaction with soil as an 2D or 3D element along with contact properties. Give me suggestion or methods how can i model soil.Suggested reading materials.I have gone through the abaqus documentation.It tell that soil can be modeled as 2D or 3D.I am really confused which one to use. 

Please give me some steps in creating soil and pipe model .

Regards

Shiva