Abstract:everse circulation DTH hammer drilling technique which has been developed and innovated on the basis of conventional fluid circulation DTH hammer drilling technique combines together three advanced methods-DTH hammer's percussive rock breaking, transportation of cuttings by reverse circulation and continuous coring during drilling operations. So it finds wide application in the fields of mineral and geological coring exploration, hydrogeological water well drilling, large diameter rock embedded foundation pile boring. Because of this technique's application, many difficulties of engineering drilling have been overcome, remarkable benefits have been achieved.The software of microcomputer calculation of artificial imitation on DTH hammer and its optimizing design on DTH hammer drilling parameters have been done to reveal the internal power process and rules of DTH hammer in detail so that scientific significance of DTH hammer design is increased. Because microcomputer calculation shows almost the same results as lab measurement, the process of testing the DTH has been simplified and the developing time is shortened.The development of series hollow-through DTH hammer constitutes the foundation of reverse circulation DTH hammer drilling technique. In DTH hammer a central hollow passageway is designed to allow reverse circulating medium, cores and cuttings to get through. Because of its proper structure, its working characteristics are exellent and reliable.In order to establish a stable, reliable reverse circulation flow to perform continous sampling during drilling operations, a bit suitable for reverse circulation DTH hammer drilling has been specially developed and manufactured successfully. This special bit may insure circulating medium flow into the central passageway to carry cores and cuttings toward the surface and never results in core blockage.Reverse circulation DTH hammer drilling technique has been widely applied in many fields such as engineering drilling. In solid mineral exploration in complex formations which are extremely hard to penetrate, easily fractured and collapsed, low coring recovery rate, etc. this technique shows its significant efficiency, every drill index increases obviously. In hydrogeological, water-well drilling through the rock this technique has completely overcome following difficulties: difficult to remove the fragments, no way to core and dust pollution around the hole top. Then this technique becomes more and more perfect. Applied in large diameter foundation pile boring, this technique may increase efficiency over 10 times compared with the conventional drilling methods, shorten construction period obviously and improve drilling quality greatly.
