Process for guiding the excavation tool used in order to execute the trenches necessary for the construction, by successive or alternating panels, of a wall cast in the ground, according to which:a) an excavation tool fitted with a first guiding element is provided,b) at the end of a previously executed trench, a second guiding element is arranged extending substantially over the entire depth of this trench, and thenc) after construction of the panel in the previously executed trench, the guiding elements are mutually engaged; andd) the excavation tool is controlled so as to create a force tending to keep the guiding elements mutually engaged while the excavation of the following trench is performed.