Head for injecting a fluid under pressure to break up ground from a borehole

A head for injecting a fluid under pressure to break up ground from a borehole, wherein said head has a longitudinal axis and is mounted to a string of rods or tubes having a bottom end, said string including a first feed pipe having a bottom end and disposed coaxially with said string of rods for feeding fluid under pressure, said head comprising:

• a body having a top end connected to the bottom end of the string of rods or tubes;
• a bottom wall;
• a mechanical drilling tooling mounted on said bottom wall and including a second feed pipe;
• an outer wall connected to said bottom wall;
• at least one injection nozzle mounted in said outer wall, said at least one injection nozzle having:
• an inlet having a diameter;
• and
• an axis;
• a duct located inside said outer wall and above said bottom wall, connecting said first feed pipe to the inlet of said at least one injection nozzle, said duct having:
• a first end connected to the bottom end of said first feed pipe:
• a second end connected tangentially to said axis of the at least one injection nozzle, wherein a cross-section said duct decreases regularly over at least half of its length from its first end to its second end;
• at least one curved portion defining a mean line and presenting a radius of curvature that varies continuously,
• a chamber disposed at the bottom wall of said head;
• at least one feed channel for feeding said mechanical tool with fluid under pressure, said at least one feed channel having a first end end a second end, wherein the first end of said at least one feed channel is connected to the first end of the duct, and wherein the second end of said at least one feed channel is connected to said chamber;
• and
• a controllable valve interposed between said chamber and said second feed pipe of said mechanical tool.