Patent ID: 8550191

Claim:
An excavation tool comprising: an excavation bit arranged on a tip portion of a casing pipe; and a device which is arranged inside the casing pipe and inside the excavation bit coaxial to an axis, and receives impact, thrust, and rotational force from the excavation tool: wherein the device has: a discharge flute, which is for discharging waste rocks produced during excavation and is formed in an outer peripheral surface along the axis toward a rear end side; and also has a fluid supply hole which extends along the axis, wherein the excavation bit includes: a tip face formed by a flat surface portion connected to a skirt portion extending in a direction opposite from the tip face and the skirt portion receiving a part of the device therein and receiving the rotational force, thrust, and impact from the device; a fluid discharge hole, which is connected to the fluid supply hole of the device and is open into the tip face of the excavation bit; a face flute, which is formed in the tip face of the excavation bit and extends radially outward; a connection flute which is formed in an outer peripheral surface of the excavation bit, is integrally connected to an outer peripheral end of the face flute, and extends toward the rear end side; and an intake hole, which is open from the connection flute into an inner peripheral side of the skirt portion, and wherein a shield wall which greatly extends radially outward beyond a casing shoe, is formed at a rear end of the connection flute.