UNDERWATER ROCK CRUSHING METHOD USING LARGE-DIAMETER HOLES FOR INCREASING ROCK-CUTTING EFFICIENCY BY SECURING DEEP HOLES AND A WIDE FREE SURFACE

摘要

PURPOSE: An underwater rock crushing method by using a large-diameter hole is provided to obtain a wide free surface by making plural large-diameter holes at regular intervals and to improve rock-cutting efficiency by applying shock by a large rock cutting bar and generating tension crack on an area between the free surfaces of the holes. CONSTITUTION: An underwater rock crushing method by using a large-diameter hole moves a rock breaking barge(20) installed with a jib crane(10) toward a rock to be cut(30), stops the rock breaking barge by settling anchors of the rock breaking barge on a base rock separated from a barge body at the predetermined distance, lifts a rock cutting bar(12) hung at a hoist rope(11) of the jib crane wound around a drum up to the predetermined height, and then hits the rock by falling freely the rock cutting bar. Before a rock cutting bar hitting step, large-diameter holes of 100¯300mm phi are drilled through the rock at the dept of 1¯10m and arranged at the predetermined intervals to secure a wide free surface. A middle spot between the adjacent holes is set as a hit target spot(A). Therefore, the rock is struck repeatedly by lifting vertically the rock cutting bar from the hit target spot and then freely dropping the bar.