To provide an inner excavation tip enlarged foot protection method of a foundation hollow pile which is implemented by using an enlarged blade, wherein the expansion/contraction of the enlarged blade is positively carried out by using the entire weight of an apparatus for use in the method, in addition to a pressurizing force, in a manner of improving energy utilization efficiency, and wherein an enlarged excavation state can be checked from a ground location, and to provide the apparatus for use in the method.

The apparatus for use in the inner excavation tip enlarged foot protection method of the foundation hollow pile is formed of (a) a double-pipe rod composed of an inner pipe and an outer pipe, (b) a rotary driving means for rotating the inner and the outer pipes forward and backward, (c) an inner pipe elevating means arranged at a location that is not embedded under the ground, for vertically moving only the inner pipe, (d) a vibration preventing means arranged on the outer pipe, (e) the expandable/contractible enlarging blade mounted on the inner pipe and at the tip of the double-pipe rod, (f) a support arranged between the expandable/contractible enlarging blade and a screw, and having one end connected to the tip of the outer pipe and the other end connected to the expandable/contractible enlarging blade, (g) an excavating blade arranged on the lower edge of the expandable/contractible enlarging blade, and (h) a discharge port for supplying an injection material via the interior of the inner pipe to a mounting portion of the expandable/contractible enlarging blade or in the vicinity of the same. The inner excavation tip enlarged foot protection method is implemented by using the apparatus.