Attenuation of Rod Stress in Percussive Long-Hole Drilling

In a mountain tunnel, predicting geological conditions ahead of the tunnel face is quite important in order to carry out the tunnel construction safely and economically. In the logging survey performed while drilling, which is one of the forward investigations of the tunnel face, drilling data such as percussive pressure, rotational pressure, feed pressure, damping pressure, and speed of the hydraulic drill are measured, and the ground state of the drilling position is predicted. Among them, the damping pressure, which damps the repulsive force from the ground due to the impact of the hydraulic drill, provides information on the geological properties of the hole drilling position. To evaluate geological properties such as compressive strength using drilling data, drilling was performed on specimens that simulated grounds with different compressive strengths, and drilling data was measured. As a result, it was found that pulsation, which is the fluctuation of pressure, was generated at damping pressure owing to the impact of the hydraulic drill. The ratio of the pulsation amplitude to the percussive pressure is a stronger correlation with the compressive strength of simulated specimens than does the specific energy.

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Estimation of Compressive Strength of Rocks Using Damping Pressure Pulsation of Hydraulic Rock Drill

Tsukamoto

Koizumi

Shinji

2019

J. Soc. Mat. Sci., Japan

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Force-Penetration Curves with a Worn Button Bit in the Percussive Long-Hole Drilling

Fukui

Abe

Koizumi

et al. 2008

Journal of the Mining and Materials Processing Institute of Jap

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A force-penetration relationship is considered to be closely related to the deformation and fracture mechanism at the bit-rock interface. In this study, a series of percussive long-hole drilling tests using Inada granite were carried out to examine the effects of hole length on drilling performace. Stress wave was measured by a pair of strain gauges, and then force-penetration curve of a button bit was calculated by the measured stress wave. The main results are summarized as follows: 1) It can be said that characteristic impedance of hard metal chips has negligible effect on the calculated force-penetration curve, but characteristic impedance of the bit and travelling time from strain gauges to the bit have considerable effect. 2) With increase of hole length, the energy transmitted to the rock decreases, damage around the bottom of the hole decreases, and then the variation in slope of each force-penetration curve decreases. 3) Average advance per blow of rock drill can be expressed by following equations: (Average advance per blow of rock drill) = 0.26× (Maximum penetration) = 0.51× (Final penetration) .

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Force-Penetration Curves with a Button Bit in the Percussive Drilling

Fukui

Okubo

Koizumi

et al. 2010

Journal of the Mining and Materials Processing Institute of Jap

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A force-penetration relationship is considered to be closely related to the deformation and fracture mechanism at the bit-rock interface. In this study, a testing machine in which a piston, a rod or a bit can be easily changed was developed for laboratory impact-penetration test simulating the in-situ percussive drilling. A series of percussive drilling tests with a button bit against Inada granite were carried out to examine and discuss the drilling performace. Stress waves were measured at two locations 1.91 m apart along the rod, and then force-penetration curve of the button bit was calculated by measured strain/stress wave. Main results are summarized as follows: 1) Delay of traveling time at bit can be expressed by a slit bit model.2) Variation in the slope of force-penetration curves in laboratory tests was very similar to that in in-situ percussive drilling. 3) In spite of large scatter in the slope of force-penetration curves, the elastic deformations of rock surface were almost constant.

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Attenuation of Rod Stress in Percussive Long-Hole Drilling

Cited by 8 publications

References 13 publications

Estimation of Compressive Strength of Rocks Using Damping Pressure Pulsation of Hydraulic Rock Drill

Estimation of Compressive Strength of Rocks Using Damping Pressure Pulsation of Hydraulic Rock Drill

Force-Penetration Curves with a Worn Button Bit in the Percussive Long-Hole Drilling

Force-Penetration Curves with a Button Bit in the Percussive Drilling

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