I am doing analysis on a sheet pile headwall for a CMP culvert under a railroad. I have been looking but have been able to figure out how to determine the lateral pressure from a strip load surcharge when the backfill has a 1:2 slope. I orginally just used the Bousinesq formula, but because of the slope and distance from the centerline of track, it seems that this may be much too conservative.

I was looking at this thread thread255-150849: Surcharge Pressure on Retaining Walls , the last post mentions a reference from Poland, and I really wish I knew the exact source so that I could include it in my calculations, at least for why the surcharge won't need to be included.  Does anybody know of a publication that refers to how to calculate the "Clear distance to surcharge"?