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△加拿大在拉布拉多地槽勘探多孔隙易碎的风化淋滤型富铁矿时，先后试用七种钻进和取心方法，结果以双管反循环取心钻进最为成功，并使日进尺达到64米，样品质量符合工程要求，此法已在该矿区推广采用。双管反循环钻进采用双管钻柱，钻井液（水）和空气由内外管间隙送入，经钻头和内管返回地表。钻进时用特制三牙轮钻头，采取岩样呈碎屑状，由于及时返出地表，判层准确性良好。为了保护孔壁，特别在深孔钻进时，采用了特种高分子（Quick-trol）泥浆循环。
In Canada, when drilling for porous friable and brittle weathering and leaching iron-rich ore in the Labrador Trough, seven drilling and coring methods were tested in succession. The result was that the most successful double-tube reverse circulation coring drilling Progressive footage reached 64 meters, sample quality in line with engineering requirements, this method has been in the mining area to promote the use of. Double reverse circulation drilling using dual-pipe drill string, drilling fluid (water) and air from the internal and external pipe into the gap, the drill bit and the inner tube back to the surface. When drilling with a special tricone bit, take a rock sample was crumbs, due to the timely return from the surface, the sub-layer accuracy is good. In order to protect the cell walls, a special Quick-trol mud circulation is used, especially when deep holes are drilled.