Abstract
This study suggests a method for quantitatively estimating the drilling performance of the down-the-hole (DTH) hammer during percussive drilling of rock surfaces. A pneumatic dynamic model of the DTH hammer was developed that considers the mass flow rate relations representing the orifice opening areas of the air tube, the piston, and bit flushing channels. A drill bit motion model was developed to represent the dynamics of a drill bit impacted by a dropped piston and explain the impact stress propagation and rock-crushing mechanism. The rock-crushing effect of the drill button bit was measured through a piston drop test. The pneumatic hammer model and drill bit motion model were then combined in a prediction model to determine the impact efficiency according to different rock types (i.e., soft, medium-hard, and very hard). The drilling efficiency was defined as the input value of the prediction model, which was used to simulate the drilling performance of DTH hammers considering the rock type and dynamic effect of the drill bit. Finally, the simulation results were compared with the results of in situ drilling tests for verification.
Highlights
Percussive drilling tools are used to extract underground resources, such as petroleum, shale gas, and minerals, and shape blasting holes for tunneling and rock excavation.ese tools are typically categorized as either down-the-hole (DTH) or top-hammer drilling, depending on the delivery method and location of the impact force
Ese tools are typically categorized as either down-the-hole (DTH) or top-hammer drilling, depending on the delivery method and location of the impact force
Many studies have focused on percussive drilling tools, few have examined the effect of rock properties on the percussive drilling performance of the DTH hammer
Summary
Percussive drilling tools are used to extract underground resources, such as petroleum, shale gas, and minerals, and shape blasting holes for tunneling and rock excavation. Many studies have focused on percussive drilling tools, few have examined the effect of rock properties on the percussive drilling performance of the DTH hammer. A new method was developed for predicting the drilling performance of a DTH hammer. The percussive drilling performance of the DTH hammer was analyzed considering the effect of the rock strength.
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