Drilling apparatus and PHC pipe cased pile, and method of drilling with PHC pipe cased pile

A method of drilling with prestressed high strength concrete (PHC) pipe cased pile, comprising steps of:

• providing a drilling apparatus, comprising a PHC pipe cased pile and a hammer element arranged inside a cavity formed by a pipe wall of the PHC pipe cased pile, the PHC pipe cased pile includes a drilling section at a distal end, the cavity is used for containing water at the drilling section;
• the hammer element moves along a drilling direction till a bottom of the drilling section;
• at least one through hole is arranged on the pipe wall of the PHC pipe cased pile at the drilling section;
• drilling and forming a drilled bore, and installing the PHC pipe cased pile;
• injecting water into the cavity of the PHC pipe cased pile at the drilling section;
• and
• driving the hammer element down to a bottom of the PHC pipe cased pile;
• as the hammer element moves down, the water in the cavity is forced to scour out rocks and soil underneath, and flows up outside the pipe wall along a gap between the PHC pipe cased pile and the rocks, then flows back to the cavity of the PHC pipe cased pile via the at least one through hole, thus forming a water circulation to scour out the rocks and soil.