Box culvert pressure to bearing soil

[Mixtli]

Hi Everyone,
I am wondering what would be the best approach to consider the soil structure interaction:
CHBDC specifies that the reaction pressure on the bottom of the box shall be considered uniformly distributed,
but I tend to do a spring analogy, I think it reflects more the real thing for this 8.7 c2c span box culvert.

What do you guys think?

Thanks a lot

Tony