Water bottom resource collecting method

A water bottom resource collecting method for drilling mud of a water bottom in an undrilled state which contains water bottom resources and lifting the mud above a surface of water covering the water bottom, the water bottom resource collecting method comprising:

• in a state where a mining riser pipe is extended from above the water toward the water bottom and at least a lower portion of an insertion pipe connected to a lower portion of the mining riser pipe is inserted in the water bottom, supplying a liquid into the insertion pipe and rotating a rotation shaft that extends inside the mining riser pipe and the insertion pipe in a pipe axial direction and a stirring blade attached to a lower portion of the rotation shaft inside the insertion pipe, thereby drilling and dissolving the mud into a slurry form inside the insertion pipe by using the stirring blade;
• raising the slurry form mud to an upper portion of the insertion pipe by using a stirring flow generated by the rotation of the stirring blade;
• and
• lifting the raised slurry form mud above the water surface through the mining riser pipe by using a pump, wherein
• a rotation speed of the stirring blade is lower in an initial process at an early stage of drilling than in a subsequent process after the initial process,
• the liquid is jetted from a jet nozzle provided on a tip end portion of the stirring blade obliquely frontward relative to a rotational direction of the stirring blade toward an inner peripheral surface of the insertion pipe, and
• the liquid is jetted from an ejection nozzle provided in the rotation shaft toward a surface of the stirring blade.