Steepness of RR track embankments

[OldEastRR]

This is for a track rising to clear a road/viaduct, dirt fill, single track. What angle is usually used for the slope?

[nkalanaga]

"Angle of repose".  Whatever the fill is stable at, which depends somewhat on the material and how wet the area is.

https://en.wikipedia.org/wiki/Angle_of_repose

You could probably get away with 30 to 40 degrees.  If going by the width of the base, I'd say 1.5 to 2 times the height, from the centerline.  For each inch of height, the base would be 3 to 4 inches wide, plus the width of flat roadbed.  Fills take a lot more room than many people think!

[Maletrain]

The trackage specs I have for the B&O use roadbed side slopes of
1.5(horizontal):1(vertical) for earth fill,
0.5:1 for loose rock, and
0.25:1 for solid rock.

These apply to the roadbed, not the ballast.  The outer ballast edge is usually specified as about 2' from the beginning of the roadbed edge downward slope.  (On the B&O, this was often clearly distinguishable by the light limestone ballast being placed on dark cinder roadbed material - with some pride being shown by the straightness of the contrasting ballast edge on recently maintained track.)

The ballast edge is specfified as roughly 7' from the track centerline, with slight variations on the basis of the class of the track.