EduMine

Mining Field: Infrastructure and Transportation Area: Surface Railroads (Rule#550)
For preliminary calculations and estimates, a granular ballast depth of 24 inches may be assumed. The top half of the ballast will be crushed gravel (usually ¾ - 1½ inches) and the bottom portion (sub-ballast) graded gravel (typically No.4 -1 inch). This depth assumes the bearing capacity of the sub-grade (native soil) is 20 psi and the maximum unit pressure under wood ties is 65 psi. Where the sub-grade capacity is known to be less than 20 psi, it may usually be assumed that the required bearing capacity will be obtained with the use of geo-textile filter fabric. more »