The invention relates to the technical field of rotary drilling
machine drill rod salvage, and discloses a magnetic card type
fishing method for
drill dropping during rotary drilling of a large-
diameter cast-in-place
pile. The magnetic card type
fishing method comprises the steps that S1, preparation work before salvage is conducted, specifically, the detailed situation of
drill falling in a hole is known, and salvage materials are prepared; S2, sediments around a drill rod in the hole are removed through reverse circulation till a
drill bit of a falling drilling tool is completely exposed, and the sediments in the hole are removed downwards as far as possible; S3, a fisher is manufactured according to the
diameter of the
pile hole and the
diameter of the drill rod, and a steel
wire rope and the fisher are fixed through a
shackle; S4, the fisher is placed, the fisher is provided with a clamping area and comprises a
magnet block used for adsorbing the drill rod, and the fisher is lowered to the
magnet block to effectively adsorb a protruding part of the drill rod connector on the surface of the drill rod, S5, the fisher enters the hole and is attracted to the outer surface of the drill rod in the hole through a movable
magnet block; S6, the steel
wire rope is lifted, so that the protruding part of the drill rod connector is clamped into the clamping area; and S7, the steel
wire rope is lifted to fish the drill rod out of the hole.