Shaft enlargement arrangement for a boring system

A boring system including a shaft enlargement arrangement, the shaft enlargement arrangement comprising:

• a hollow column proximate a lower end of the boring system;
• a first cutter head that is rotatably fitted to the hollow column, with first drive means being provided to rotate the first cutter head relative to the hollow column so as to bore downwardly a hole having a diameter corresponding substantially to the diameter of the first cutter head, the first cutter head comprising a support body carrying a winged arrangement, the support body being rotatably fitted to the column, the winged arrangement comprising a plurality of wings extending from the support body, each wing being fitted with, or comprising, a plurality of first cutter elements, each wing being angled upwardly and away from the support body so to define a substantially V-shaped cutting profile;
• a boring head arrangement fitted to an operatively lower end of the column, the boring head arrangement terminating in a second cutter head to bore a leading hole as the boring system proceeds to bore downwardly;
• a lower collecting bunker provided below the first cutter head, into which cuttings produced by the rotating first cutter head can be collected, the lower collecting bunker including a bunker body defining an inlet chute opening to receive the cuttings, and an outlet chute exit that is in line with a corresponding aperture defined in the column through which the cuttings can exit the bunker into the column for subsequent collection by an inner kibble travelling up and down the column;
• and
• a gripper arrangement fitted to the hollow column, the gripper arrangement being positioned, in use, below the lower collecting bunker and above the boring head arrangement, the gripper arrangement being arranged to securely grip against the leading hole bored by the second cutter head, so as to secure the boring system in position within the bored hole, the gripper arrangement including a pair of diametrically opposed clamps that extend sidewardly away from the hollow column, the clamps being movable between a retracted, disengaged position and an extended, engaged position in which the clamps clamp against the leading hole defined by the second cutter head to facilitate and/or control rotation of the first cutter head.