Railroad width: 368 px/143.51 cm (the average with comes at 4’8.5”)
Pile diameter: 951 px/370.864157609 cm (radius is 185.432078804 cm)
Pile height: 408 px/159.108913043 cm
Volume (Cone): (Pi*185.432078804^2)(159.108913043/3) is 5729185.19407 cm^3
Gonna assume 10% hollowness as it is a pile. That is 5156266.67466 cm^3
He destroyed it in 3 shots. Most of the rocks are nowhere to be seen, only being reduced to a few still visible, so I suppose Violent Fragmentation could work.
(69*5156266.67466)/3 is 118594133.517 joules/118.594133517 megajoules, or Small Building level