The present invention relates to a machine for digging a trench and making a wall in said trench, the machine being suitable for advancing along a path and having rear and front portions relative to the direction of advance of the machine, together with excavator means disposed in the front portion of the machine and defining a substantially vertical cutting front; wall-forming means situated in the rear portion of the machine; and propulsion means suitable for causing the machine to advance along said path. The machine also has a central portion, controllable brake means for slowing advance or blocking at least one portion of the machine, and controllable connection and disconnection means for connecting and disconnecting the central portion respectively with the front and rear portions of the machine, thereby enabling the type of excavator means and the type of wall-forming means to be changed.