Lateral Pressures on Retaining Walls from Surcharges, Das vs AASHTO 1

[SG2010]

I am confused about a discrepancy between the equations calculating the lateral pressure on a wall due to surcharge loading, as defined in Principles of Geotechnical Engineering (Braja M. Das) and the same equation as provided in AASHTO LRFD Bridge Design Specifications. I have attached cut sheet images below for reference.

These two equations appear to be very similar, with the exception that Das divides the pressure by height of wall, H and AASHTO divides by Pi. It could be a result of unit conversion or some obvious trig that I am misunderstanding, but it doesn't seem to make much sense to have it be dependent on H. For a large wall height of say 30', Equation 12.23 would reduce this localized pressure near the top of the wall by nearly 10x. I couldn't find this discussed before in this forum, but if anyone has any input on the utilization of either of these two equations I would appreciate it.

Thank you!

 

[SG2010]

I realize the clips from Chapter 12 from Das did not come in cleary. Re-attached them below.

 

[r13]

I think it is depends on the method used. Below is using so called "Elastic Method".

 

[Kevin9679]

All of them are conservative.