Top Hammer Drill Simulation in Varying Rock Conditions

Abstract

Rock breaking using a top hammer drill is achieved with a combination of four distinct hydraulically driven functions; percussion, feed, rotation and flushing the hole. Percussion, feed and rotation are applied to the drill string outside the drill hole. Flushing water or another flushing medium is pumped through the drill string to the bit. Controlling top hammer drill rigs in varying rock conditions is an important task, as non-optimal control can damage drilling equipment and waste energy. Damage occur especially when percussion-induced stress waves are not optimally transmitted to the rock and are thus reflected from the drill bit–rock interface to the drill. Therefore, to design an adaptive control system to manage drilling in all rock conditions, it is meaningful to develop a simulator that can produce data comparable to real-life drilling. This paper presents a rock drill simulator designed in MATLAB/Simulink environment. The rock drill model has hydraulic feed and rotation circuits, and drill string is modeled as a finite element beam having three degrees of freedom per node and two nodes per element. A total of 90 elements were used for the drill string modeling. The simulation also includes a rock model that can be modified to emulate varying rock conditions. By modifying the parameters of the rock model and boundary conditions, penetration rate changes and the simulated strain from the drill string varies.