• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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• pp.52-57
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• 1999

Korea Earthquake Monitoring System(KEMS) in the Korea Institute of Geology Mining and Materials(KIGAM) as detected more than 1000 events since the end of 1998. But not all events are interpreted as earthquakes because many events are concentrated on daytime. It strongly implies that in addition to earthquake these events include artificial effects such as industrial blasting. Before the determination of eathquake charactertistics in the korean peninsula it is necessary to discriminate the detected events as earthquakes or artificial events. For the discriminant study KIGAM and SMU(Southern Methodist University) installed a triangular four-element 1-km aperture seismo-acoustic array at Chul-Won area northeast of Seoul Korea. Each array element includes a GS-13 seismometer in the bottom of borehole and a Validyne DP250-14 microbarometer sensor mounted inside of the borehole 1,2 meter deep connected to a 11 arm radial array of 10m porous soaker hoses. This array introduce the use of 2.4-GHz radios for inter-array self-contained solar-charged power system and GPS time-keeping system. A 24-bit digital data acquisition system performs 40 SPS in the infrasound and seismometer data. Velocity and direction of wind and temperature are also measured at hub site and included to the data stresam. This seismo-acoustic array will be used to identify and locate associated with industrial blasting and these identified and located events will be applied to form a ground truth database useful to assist the other development of discriminant studies.

• Tunnel and Underground Space
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• v.12 no.3
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• pp.179-188
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• 2002

This study is to understand the effect of the vibration and the stress changes due to the excavation of 2 arch parts of a tunnel, which is a Gyungbu Express Railway tunnel, on the tunnel itself and adjacent slopes in advance, and to analyze the stability. For the estimation of ground conditions, borehole tests, borehole camera logging and seismic logging were performed. Ground properties at a specific location were determined as input constants by performing 2 dimensional analyses with possible ranges of uncertain ground properties. Static and pseudo-static (due to blasting vibration) factors of safety were calculated. The behavior of the tunnel and its vicinity due to the tunnel excavation were predicted by 3 dimensional analyses. It was also tested whether the support system was proper.

• Computers and Concrete
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• v.25 no.2
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• pp.145-154
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• 2020

For the influence of the propagation law of stress wave at the coal-rock interface during the pre-blasting of the top coal in top coal mining, the ANSYS-LS/DYNA fluid-solid coupling algorithm was used to numerical calculation and the life-death element method was used to simulate the propagation of explosion cracks. The equation of the crushing zone and the fracturing zone were derived. The results were calculated and showed that the crushing radius is 14.6 cm and the fracturing radius is 35.8 cm. With the increase of the angles between the borehole and the coal-rock interface, the vibration velocity of the coal particles and the rock particles at the interface decreases gradually, and the transmission coefficient of the stress wave from the coal mass into the rock mass decreases gradually. When the angle between the borehole and the coal-rock interface is 0°, the overall crushing degree is about 11% and up to the largest. With the increase of the distance from the charge to the coal-rock interface, the stress wave transmission coefficient and the crushing degree of the coal-rock are gradually decreased. At the distance of 50 cm, the crushing degree of the coal-rock reached the maximum of approximately 12.3%.

• Explosives and Blasting
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• v.31 no.2
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• pp.40-49
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• 2013

To predict ground conditions ahead of the tunnel face, seismic refraction survey has been widely used. But due to the development in seismic equipment and techniques, tomography using borehole and others are actively applied in recent years. This study has a purpose to prevent stability problems during excavation and construction of tunnels by predicting unfavorable ground conditions such as fault, fractured zone and rock quality variation zone ahead of the tunnel face using TSP survey equipment. In this study, the validity of predicting ground conditions ahead of tunnel face by TSP survey has been evaluated through the case study in the road construction site.

• Explosives and Blasting
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• v.18 no.3
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• pp.15-28
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• 2000

국내에서는 Heavy ANFO로 더 잘 알려져 있는 Emulsion Blends는 왁스 대신 오일을 사용 하여 상온에서 펌핑이 가능하도록 한 에멀젼과 ANFO(또는 초안)의 혼합물을 일컫는다. ANFO는 저렴하고 안전하며 장약이 쉽고 밀장전되는 장점이 있지만, 내수성이 거의 없고 폭발 속도가 느리며 장약 비중이 0.75∼0.90g/cc 정도로 낮아 폭약으로서 그 위력이 작은 단점을 갖고 있다. Blends는 수용성 ANFO 입자 사이의 빈 공간을 내수성 에멀젼이 태우고 있는 형태로서 에멀젼 함량 25%부터 내수성이 나타나기 시작하여 에멀젼 함량 40% 이상에서는 완전한 내수성을 갖게 되며, 에멀젼의 함량이 증가할수록 폭발속도는 카트리지 에멀젼 폭약에 근접하게 된다. 장약 비중은 에멀젼의 함량이 증가하여 45% 근처에서 1.25∼ 1.30g/cc의 최대 값을 갖지만, 그 이상의 에멀젼 함량에서는 기폭 감도 저하로 예감제를 사용하여 비중을 감소시키는 것이 바람직하다. Blends는 자체에 물을 함유하고 있으므로 열역학적으로 계산된 단위 중량당 반응열은 ANFO에 비해 매우 적지만, 폭발속도, detonation pressure(폭굉압), borehole pressure(폭발압력) 등이 ANFO에 비해 크므로 폭발압력에서부터 암석의 파괴가 가능한 압력가지의 단위 중량당 유효한 에너지의 양은 암석의 강도가 커질수록 ANFO에 비해 매우 적지만, 폭발속도, ANFO와 비슷해진다. 따라서 장약 비중이 ANFO의 130∼145%로 높은 Blends는 동일한 천공에 더 많이 장약할 수 있어 단위 천공당 암석 파괴에 이용되는 유효 에너지의 총 양이 커지게 되므로, 공간격과 저항선을 늘릴 수 있어 총 천공수를 감소시킬 수 있다. 결론적으로, Blends의 장점은 내수성과 함께 비장약량은 비슷하거나 약간 증가하는데 비해, 천공수는 크게 감소하여 전체적으로는 발파 현장의 경제성이 향상된다는데 있다.

• The Journal of Engineering Geology
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• v.31 no.3
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• pp.433-445
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• 2021

Plasma blasting by high voltage arc discharge were performed in laboratory-scale soil samples to investigate the fluid penetration efficiency. A plasma blasting device with a large-capacity capacitor and columnar soil samples with a diameter of 80 cm and a height of 60 cm were prepared. Columnar soil samples consist of seven A-samples mixed with sand and silt by ratio of 7:3 and three B-samples by ratio of 9:1. When fluid was injected into A-sample by pressure without plasma blasting, fluid penetrated into soil only near around the borehole, and penetration area ratio was less than 5%. Fluid was injected by plasma blasting with three different discharge energies of 1 kJ, 4 kJ and 9 kJ. When plasma blasting was performed once in the A-samples, penetration area ratios of the fluid were 16-25%. Penetration area ratios were 30-48% when blastings were executed five times consecutively. The largest penetration area by plasma blasting was 9.6 times larger than that by fluid injection by pressure. This indicates that the higher discharge energy of plasma blasting and the more numbers of blasting are, the larger are fluid penetration areas. When five consecutive plasma blasting were carried out in B-sample, fluid penetration area ratios were 33-59%. Penetration areas into B-samples were 1.1-1.4 times larger than those in A-samples when test conditions were the same, indicating that the higher permeability of soil is, the larger is fluid penetration area. The fluid penetration radius was calculated to figure out fluid penetration volume. When the fluid was injected by pressure, the penetration radius was 9 cm. Whereas, the penetration radius was 27-30 cm when blasting were performed 5 times with energy of 9 kJ. The radius increased up to 333% by plasma blasting. All these results indicate that cleaning agent penetrates further and remediation efficiency of contaminated soil will be improved if plasma blasting technology is applied to in situ cleaning of contaminated soil with low permeability.

• Explosives and Blasting
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• v.31 no.2
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• pp.6-13
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• 2013

Recently, complaints or environmental problems caused by the noise and dust generated from crusher of the mine and quarry are emerging. Therefore mining facilities such as crushers and mills have been installed in an underground. In order to facilitate crusher equipments in the underground, excavation of large space is required and then the stability of the large space underground structure is an important issue. In this study, the blast experiments, which use a block of the limestone, are performed. Based on the blast experiments, the numerical model was prepared and simulated using dynamic fracture process analysis code(DFPA) with considering the rising time of applied borehole pressure and microscopic tensile strength variation. Comparing the non-dimensional crack length and no-dimensional tensile strength obtained from blast experiments and numerical analyses, the input parameters of DFPA code for predicting a radial tensile crack in limestone blasting were determined.

• Tunnel and Underground Space
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• v.6 no.4
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• pp.342-347
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• 1996

The changes of electromagnetic wave velocity in rock were monitored to investigate rock behaviors due to the drill & blasting excavations through georadar tomography during the construction of the underground rock laboratory (5 m wide, 6 m high, and 140 m long) at Mabuk-Ri, Goosung-Myun, Yongin-Si, Kyunggi-Do. Two horizontal boreholes spaced 1.4 m apart were drilled parallel to the test tunnel before excavating it, high-resolution crosshole georadar tomography with about 500 MHz electromagnetic waves was performed at pre-excavation phase (May, 1996) and post-excavation phase (August, 1996). The data were acquired with the combination of 34 sources and 44 receivers with space of 0.3 m. Only 11 continuous receivers were selectively utilized with one fixed source. Sampling interval was 0.4 ns and each trace has 512 samples. The first arrival of each trace was picked manually with a picking software. The total number of rays used in inversion amounted to 34x11 and the size of pixel was determined to be 0.3 m. As an inversion technique, SIRT(Simultaneous Iterative Reconstruction Technique) was applied in this study. The velocity of electromagnetic waves at post-excavation phase decreased as large as 15% in comparison with that at pre-excavation phase, which may be attributed to the creation of micro-cracks in rock due to excavations and saturation with groundwater. Small amount of borehole deviation made a critical effect in radar tomography. Totally different tomograms were created after borehole deviation corrections.

• Explosives and Blasting
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• v.22 no.3
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• pp.103-111
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• 2004

The existing methods that can be adopted for measuring joints involve either to use borehole or photogrammetry. Due to restricted space, acquisition of data in limited area, and measurement errors, above methods have limitations acquiring the objective and correct results. To get over defects of existing joint measurement methods, joints have been measured using 3D-Laser scanner with accuracy and efficiency. This research aims to investigate an accuracy and applicabiliy of 3D-Laser scanner for measuring rock slope joints. Measurement of rock slope joints has been executed using 3D-Laser scanner & clinometer and then, results from both methods are compared. Results from both methods indicate that they show nearly equal features for joint distributions and numbers of joint information obtained by 3D-Laser scanner are much more than ones measured using clinomer. Therefore, 3D-Laser scanner turns out to be very effective by the fact that it contributes to reduce investigation costs & periods, objectify data from rock slope joints.

• Geomechanics and Engineering
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• v.13 no.5
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• pp.861-879
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• 2017

Coal and gas outburst is a serious dynamic disaster that occurs during coal mining and threatens the lives of coal miners. Currently, coal and gas outburst is commonly predicted using single indicator and its critical value. However, single indicator is unable to fully reflect all of the factors impacting outburst risk and has poor prediction accuracy. Therefore, a more accurate prediction method is necessary. In this work, we first analyzed on-site impacting factors and precursors of coal and gas outburst; then, we constructed a Fisher discriminant analysis (FDA) index system using the gas adsorption index of drilling cutting ${\Delta}h_2$, the drilling cutting weight S, the initial velocity of gas emission from borehole q, the thickness of soft coal h, and the maximum ratio of post-blasting gas emission peak to pre-blasting gas emission $B_{max}$; finally, we studied an FDA-based multiple indicators discriminant model of coal and gas outburst, and applied the discriminant model to predict coal and gas outburst. The results showed that the discriminant model has 100% prediction accuracy, even when some conventional indexes are lower than the warning criteria. The FDA method has a broad application prospects in coal and gas outburst prediction.