Investigations on rock drillability applied to underground mine development vis-à-vis drill selection

Abstract

Current underground mining scenario is inclining towards mechanized drilling and blasting since it proves advantageous in many ways like controlled excavation profile, limited ground vibrations and better ground control, higher rates of advance, enhanced mine development rates besides maintaining a balance in overall economics of the project. Considering the challenges posed by varied geological conditionsencountered in mining and civil engineering excavations, application of mechanized drilling and blasting technique still dominates. In order to meet the existing mineral demands, the development rates need to be maximized. To attain such development rates, there is an increased drill requirement which calls for an uninterrupted, consistent and a reliable drill system in place.Drilling is further affected by uncontrollable parameters like geological properties, rock structure and in-situ stresses, and controllable parameters like thrust, rpm, feed, flushing, operator's skill, working conditions, etc. Different rock drillability models have been reviewed in this paper to understand the influence of various key parameters influencing drill rates. However, it is interesting to note that not many of the drillability models consider the geology, rock drillability, machine (design and operational), bit parameters, in-situ stresses and working conditions all together. A case study of an underground hard rock mine is presented describing a mechanized drilling system for a development heading with a dimension of 3.6 m in width and 3.0 m in height using a rotary percussive electro-hydraulic drill jumbo. In order to meet a development rate of 3,600 meters per annum in a single mine, drill bits alone costs around Rs. 31.5 Lacs apart from other drilling expenses which is in fact a huge capital investment for any industry. This stresses on detailed research in this area and development of a comprehensive generalized model accounting for the key influencing variables.

[Retracted] Prediction of the Least Principal Stresses Using Drilling Data: A Machine Learning Application

“…e uniqueness of the ML is that ML can be able to find the direct and the indirect relationships between the input and the output parameters. To the best of the author's knowledge, there is no direct relationship between the drilling parameters and the in situ stresses; however, as the formation stress increases, the drillability of the formation decreases [17]. [31][32][33][34] showed that rock cuttability decreased in the stressed formations.…”

“…en, the set values of these parameters would be adjusted while drilling according to the drillability of the downhole formations which mainly depend on the stress concentration around the wellbore [17,18]. Accordingly, this would be translated into the measured values of SPP, T, and ROP.…”

“…The initial values for these parameters are usually set based on the data available from offset wells and the experience of the drilling engineer with the area. Then, the set values of these parameters would be adjusted while drilling according to the drillability of the downhole formations which mainly depend on the stress concentration around the wellbore [ 17 , 18 ]. Accordingly, this would be translated into the measured values of SPP, T, and ROP.…”