Apparatus for water jet and impact drilling and mining

Subterranean drilling and mining apparatus, comprising

• a cylindrical casing pipe to line a borehole to be formed by the apparatus;
• an inner drill string assembly movable vertically within the casing pipe and comprising an inner pipe, an intermediate pipe which is slidable in the outer casing pipe and which encompasses the inner pipe so as to define an annular clearance space between it and the inner pipe, and a drilling shoe interconnecting the bottom ends of the inner pipe and the intermediate pipe and formed with a plurality of drilling jet passages communicating with said annular clearance space;
• mining jet means comprising at least one mining nozzle extending through the wall of the intermediate pipe above the drilling shoe;
• water inlet means for admitting water under pressure to the annular clearance space between the intermediate pipe and the main pipe;
• and
• impact means for delivering impact blows to the casing pipe to drill and case a borehole by operation of the impact means to drive the casing pipe downwardly while maintaining the inner drill string assembly retracted therein sufficiently to maintain said mining jet means within the casing pipe, means for supplying water under pressure via the water inlet means to the annular clearance space between the intermediate pipe and the inner pipe to issue therefrom through the drilling jet passages as drilling jets to assist penetration of the casing pipe and means for extending the inner drill string assembly downwardly within the casing pipe to bring the mining jet means beneath the bottom end of the casing pipe to allow water under pressure to issue therethrough as at least one mining jet effective to excavate the material to be mined, the inner pipe serving as an extraction pipe for extraction of expended water and spoil during both drilling and mining operations to mine material surrounding the bottom of the bore hole.