This paper discusses the Helical Drag Bit (HDB) andits rock drilling applications with an emphasis on use inmining operations. The HDB is a drilling tool thatemploys cutting members arranged in a pattern to form ahelical groove or thread within a borehole. This patternof cutters can be used for several purposes including roofbolting in mining, interpretation of the lithology of thestrata being drilled and low energy consumption drilling.Laboratory and field experiments have consistentlyshown increase of roof bolt-anchoring capacities in weakrock of more than 100% using the short encapsulationpull test method when boreholes are conditioned using theHDB. In 2004 a series of tests conducted in mines withweak roofs demonstrated the benefits of HDB technologyfor roof bolting applications in mining.HDB technology offers opportunities for new andbeneficial approaches to interpret the geology of roofstrata. During conventional drilling, traditionalapproaches to determine rock properties requiresimultaneous measurement of several parameters such asthrust, rotational velocity, torque and penetration rate.The unique geometry of the HDB possesses acharacteristic that allows determination of the mechanicalproperties of the rock being drilled by measuring torqueas a single drilling parameter. This capability greatlysimplifies the process of determining rock properties andprovides reliable results.Additionally, HDB technology has beendemonstrated to offer significant advantages for rockdrilling. A substantial portion of the rock is removed bythe fracturing of the internal thread created in the rockbore by the tool taking advantage of the weakness of therock in tension. Because the rock chips obtained in thisprocess are relatively large, savings in energy are realizedwhen compared to traditional drilling technologies.
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