The Cooper E-80 surcharge I described above is specified by Conrail, Amtrak, Norfolk Southern, CSX, and others.
The 80,000# axle load acts on a 5 foot axle spacing and 8.5 feet wide ties. Therefore, the railroads are looking for an 1800 to 1882 psf, vertical, strip pressure used with the Boussinesq equation for a RIGID wall.