Core barrel head, inner tube assembly provided with same, and inner tube recovery method

A recovery method of an inner tube in which a geological sample has been collected, the method comprising:

• a slide tube fixing latch release step of releasing an engaged state with a latch disengagement slide tube by pressing an overshot into an outer tube and inclining a slide tube fixing latch of a core barrel head at a front end position inside the outer tube;
• a latch inclination preventing part release step of releasing a contact state of the latch inclination preventing part with an inner fixing latch by pushing the latch disengagement slide tube that is released from the engaged state toward a front end side and sliding the latch disengagement slide tube toward an axially front end side along an outer circumferential surface of a main shaft so as to move the latch inclination preventing part toward the axially front end side;
• an inner fixing latch disengagement step of disengaging the inner fixing latch from a locking groove formed on an inner wall surface of the outer tube by inclining the inner fixing latch in an inward direction against a biasing force by the latch disengagement slide tube that is slid;
• and
• an inner tube recovery step of recovering the inner tube connected to a front end of the core barrel head by connecting the overshot to a rear end portion of the core barrel head and pumping the inner tube out by water pressure of underground water that enters into the outer tube, or by pulling the inner tube out with a wire connected to the overshot.