Ground drilling device

A ground drilling device comprising:

• a rotary blade that excavates a ground;
• a lubricating liquid jetting device that jets a lubricating liquid to the rotary blade when excavating the ground;
• and
• an oxygen supply device that is disposed on the ground and supplies oxygen to the lubricating liquid,
• wherein the oxygen supply device includes a bubble generating medium for supplying oxygen having a pressure up to 1.5 megapascals (MPa) higher than the atmospheric pressure as fine bubbles to the lubricating liquid,
• the ground drilling device being a shield machine and further comprising:
• a drilling cutter having a plurality of the rotary blades;
• a partition wall having a cylindrical shape to which the drilling cutter is attached;
• a drilling chamber formed by the partition wall;
• a mud outlet opened in the partition wall;
• a high-concentration mud water facility that is disposed on the ground and mixes an injection material and an excavated soil to prepare a high-concentration mud water as the lubricating liquid;
• a discharged mud introducing pipe having one end communicated with the mud outlet to discharge an excavated soil and sand in the drilling chamber;
• a suction tank that is disposed on the ground and on one side of the high-concentration mud water facility;
• and
• a discharged mud conveying pipe that is connected to the suction tank and conveys the excavated soil and sand up to the ground,
• wherein
• the lubricating liquid jetting device includes:
• a first jetting device that jets the high-concentration mud water as the lubricating liquid from the high-concentration mud water facility to a front of the drilling cutter;
• and a second jetting device that jets the high-concentration mud water as the lubricating liquid from the high-concentration mud water facility to an outer peripheral portion of the partition wall,
• the bubble generating medium of the oxygen supply device discharges the oxygen having the pressure as the fine bubbles into the high-concentration mud water when the injection material and an excavated soil are mixed in the high-concentration mud water facility, and
• the bubble generating medium is formed of a carbon-based porous material.