Abstract: This plough adapted to be mounted on a railroad tracklaying machine comprises in its plough area members capable of disaggregating and/or thrusting aside the old compact ballast. These members consist of ejectors acting like pistons and extending through apertures formed in the ploughshares; the ejectors movable across the normal direction of travel of the plough under the control are driven by an actuating mechanism imparting a reciprocating motion thereto, and may be replaced by blades disposed beneath, and substantially parallel to, the ploughshares, the actuating mechanism being adapted to impart to these blades a movement substantially of translation along a closed path.