Rock mass classification for estimating the drilling rate in a surface mine using rock mass drillability index

Abstract

Accurate determination of drilling rate in surface mines is influenced by not only the mechanical parameters of the drilling rig but also the rock properties. The primary mechanical parameters include the rotational speed, thrust force, and air flushing pressure while the rock properties include uniaxial compressive strength (UCS), tensile strength, elastic modulus, hardness, discontinuities characteristics etc. This study has attempted to quantify the geological and geotechnical characteristics of a chromite deposit using rock drillability index (RDi) by dividing the working area into ten zones. Thereafter, considering the varied geo-mechanical properties of the deposit and the net time invested for drilling, site-specific empirical relations were formulated correlating the rock drillability index with drilling rate; Schmidt hammer rebound number with uniaxial compressive strength with correlation coefficients of 0.95 and 0.97 respectively. Lastly, a new rate of penetration model was proposed by incorporating the rock drillability index and the mechanical specifications with a correlation coefficient of 0.86. Thus, this study has successfully executed rock mass classification and justified the performance efficiency of the proposed model by its comparison with a universal model. Finally, the ten zones were grouped according to their drilling rates and quantified in terms of their drillability for optimization.

Keywords:

• Rock drillability index
• Drilling rate
• Rate of penetration
• Drilling time optimization
• Regression analysis

Acknowledgement

The authors duly acknowledge the support received from CRG-SERB vide order no. CRG/2020/006414 dated 17.12.2020.

Disclosure statement

The authors declare no conflicts of interests.