Head for injecting liquid under pressure to excavate the ground

A head for injecting a liquid under pressure from a borehole to break up the soil, said head being mounted at the end of a drill string, said string including liquid feed means for feeding a liquid under pressure, said head comprising:

• a body having a top end for connection to the bottom end of the drill string, a bottom end, and an outside wall;
• at least one injection nozzle mounted in said body, the inlet diameter of the nozzle being equal to d, and the nozzle presenting an axis (x-x′);
• a tool mounted at the bottom end of said body;
• a feed tube for feeding said tool connected to said feed means and extending into said body;
• and
• the duct-forming means presenting a first end connected substantially tangentially to said feed tube and a second end connected to said nozzle, said duct-forming means presenting a mean line whose first end is connected to said tube and whose second end is connected to the nozzle tangentially to said axis (x-x′), said mean line being defined by at least one curved portion presenting a radius of curvature that varies continuously, the right section of such duct-forming means decreasing regularly over at least half of its length from its first end to its second end.