DRILLING TECHNIQUES OF LARGE DIAMETER HOLES FOR THE FOUNDATION PILES OF QOM BRIDGE IN IRAN

The author introduced a successful experience of reverse circulation drilling with pumping in Iran. The technical problems in construction of large diameter holes were solved,including the covering of muff,shifting and positioning of the drilling rig,improving of the welding angles of the fishtailed and swallowtailed drag bits and the exchange of sealing materials of pumps etc. The construction of the foundation piles of Qom Bridge reached a good result with high efficiency and fine quality.