Abstract
A detailed understanding of the drilling system and the drilling control is required to correctly interpret rock mass conditions based on monitored drilling data. This paper analyses data from hydraulic in-the-hole (ITH) drills used in LKAB’s Malmberget mine in Sweden. Drill parameters, including penetration rate, percussive pressure, feed pressure, and rotation pressure, are monitored in underground production holes. Calculated parameters, penetration rate variability, rotation pressure variability, and fracturing are included in the analysis to improve the opportunity to predict rock mass conditions. Principal component analysis (PCA) is used to address non-linearity and variable interactions. The results show that the data contain pronounced hole length-dependent trends, both linear and step-wise linear, for most parameters. It is also suggested that monitoring can be an efficient way to optimize target values for drill parameters, as demonstrated for feed force. Finally, principal component analysis can be used to transfer a number of drill parameters into single components with a more straightforward geomechanical meaning.
Highlights
Over recent decades, drill monitoring, or measurement while drilling (MWD), has become a well-established technique to characterize the penetrated rock mass in the mining and petroleum industries [1]
Variability parameters: The penetration rate variability and rotation pressure variability have been used in field tests, with both parameters found to be sensitive to rock fracturing [21]
It has been argued that, for ITH drilling, the penetration rate should not decrease with hole length, as the hammer is located at the end of the drill string acting directly on the rock
Summary
Drill monitoring, or measurement while drilling (MWD), has become a well-established technique to characterize the penetrated rock mass in the mining and petroleum industries [1]. The most important monitored drill parameters are penetration rate, percussive pressure, feed pressure, and rotation pressure. Variations in these parameters along the length of the hole, is the result from the combined effect of variations in the properties of the penetrated rock mass, drill operators, and drill control systems [6,14]. A descriptive drilling response is increased signal variability, for rotation pressure recorded parameter independently describe the characteristics of the rock mass a conclusivevariability and penetration rates whencannot fractured or inhomogeneous rock is encountered. The analysis suggests a better rock mass model can be developed by understanding and eliminating the variations caused by the external influence of operators and drill control systems. Eliminatingand the variations caused by the external influence of operators and drill control systems
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