Greetings,

I am modeling a 6" electrical conduit (di-elctrically filled with oil at 170F) that runs for several thousands of feet. Most of the length, the soil will be either native soil or engineered fill. There are several section that cross under city streets close to the surface (with in 4' of the road). Under these sections, the profile from grade to pipe is stratified into asphalt, compacted sand and gravel.

My question: While the pipe is still encased by engineered fill or native soil at these areas, is it still correct to allow Caesar to assume the soil is homogenious all the way up through grade? I would think the old parameter that might be different is the pressure due to a density change. The friction coefficient and all other soil properties should be the same. Is this assumption correct to make?

old =only. Sorry lack of coffee

Of course there's lots of uncertainty in modeling "nature" or the "real world".
I would suggest you examine the results of several models to bracket the possible response.