Broad-foot concrete foundation pile - is cast in-situ after drilling with lost-point drill head on tube, head producing void on withdrawal

摘要

The arrangement is intended for producing a reinforced concrete foundation pile in the ground with a broad lower end. A steel tube (2) carries a conical helical drilling head (3;4,5), with a loose point (6) coupled to the head via circumferentially acting one-way stops (7). The point is left on withdrawal of the tube, after the reinforcement is placed and concrete poured. The tube is screwed down under axial pressure. When the required depth is reached, it is unscrewed under upward axial force which is such that the tube moves upwards at greater rate than determined by the screw pitch of the drilling head, thus producing a void in the lower end of the bore hole. This void fills with concrete to produce the broad foot which provides a calculable increase in effective bearing load.FL.