ABSTRACT

The present paper deals with the determination of specific energy at different thrust and bit rotational speed of rocks namely Makrana marble, sandstones and coal having varying strength using dragbit and microbit. The specific energy so evaluated are correlated with strength parameters (compressive strength, shear strength, tensile strength and Schmidt hardness number) . These properties have shown good correlation with specific energy. Specific energy determined from microbit drilling comensurates the results for full scale drilling. Predictive equations have been arrived at from statistical regression analysis. The results from rotary and microbit drilling have lead to the conclusion that specific energy could be considered as a reliable parameter to predict drillability of rocks.