• Explosives and Blasting
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• v.23 no.1
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• pp.41-46
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• 2005

Overbreak is an inevitable during tunnel excavation. It significantly affects tunnel construction cost and safety The overbreak occurs due to incorrect expectations to the geologic structures, excessive charge or strength of explosives, etc. This paper introduces multi-hole drilling method to minimize the overbreak in tunnel excavation. Although the drilling cost of the method is more expensive than those of the existing other drilling method, it is expected at that cost will be reduced.

• Korean Journal of Soil Science and Fertilizer
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• v.27 no.2
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• pp.117-124
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• 1994

A study was conducted to dectermine the days with optimum soil moisture after drainage or rain for machine workability and seeding establishment on dry seeding in paddy soils(Jeon buk Series, Haplaquepts). The results are summarized as follows. 1. The possible days of tractor-rotary plough were 5days or more for non-mole hole plot(control). The possible days were 2~4days and the optimum days were 5~6days for mole hale plat. 2. The ratio of soil clod(<1cm) was 1 % and 15% for control and mole hole plats, respectively. The optimum soil moisture range for seeding establishment was 31~32% in this soils. 3. The possible days of combine harvesting work were 9days and 5days after drainage for control and mole hole plots, respectively. 4. Soil physical properties were improved but soil organic matter calcium and magnesium in the soil were decreased in the mole hole plats. 5. Yield was 415kg/10a at seeding after 6day drainage in control and 440kg/10a at seeding after 4day drainage in the mole plots.

• Explosives and Blasting
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• v.38 no.1
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• pp.14-22
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• 2020

Bit damage is one of the primary causes of decreasing drilling efficacy. Nevertheless the management of bit ware and failure are often left for field engineers' experience. Thus it is imperative to establish a proper system to predict and manage the bit damage during the rock drilling process. In this study, the drilling sound signal has been recorded and analyzed using wavelet transform analysis to identify the exact moment of bit failure. Through the analysis wavelet time-frequency spectrums have been constructed and an abnormal point has been identified with 0.9 of wavelet transform value at the 652.8s on a frequency band around 500Hz. Furthermore it is also observed that the penetration rate of the damaged bit has been decreased to 23mm/s which is 9mm/sec lower than the average of undamaged bit. The study verifies that wavelet transform analysis can be used to build a system to diagnose the bit damage while drilling.

• Explosives and Blasting
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• v.25 no.1
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• pp.67-77
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• 2007

The drill monitoring data are useful for the detection of abrupt and unexpected changes in ground renditions. This paper introduces a new approach to how drill performance parameters can be used for the prediction of quantitative rock mass properties ahead of tunnel face and the blasting design. The drill monitoring parameters available for the predictions include the instantaneous advance speed, thrust force, torque, tool pressure and penetration rate. The assessment of the drill monitoring parameters will be able to build a database provided that in-situ drill monitoring informations are accumulated and enable us to make a reasonable blast design based on quantitative assessment of rock mass.

• Explosives and Blasting
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• v.19 no.3
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• pp.115-117
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• 2001

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2001.10a
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• pp.219-222
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• 2001

• Tunnel and Underground Space
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• v.23 no.1
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• pp.42-53
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• 2013

The percussion rate and spacing of the button of drill bit are very important in maximizing the drilling efficiency. Therefore, a series of percussion tests using Hopkinson bar system was carried out to assess the fragmentation performance against the beat rate and spacing of a drill bit. First, single percussion test complemented with numerical simulation was performed to analyze rock fragmentation phenomenon and to describe the fragmentation process. Next, multiple percussion test that repetitively strike the rock sample moving at predetermined rate was carried out to predict drilling efficiency against the button spacing. After the tests, the fragmented volume of the rock was measured by laser scanner and the drilling performance was analyzed using the calculated percussive energy and measured negative volume. Based on the results, the single impact performance of drill bit with 102 mm diameter was predicted.

• Journal of agriculture & life science
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• v.50 no.5
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• pp.217-224
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• 2016

In this study, performance of a developed automatic punching machine considering the planting density of soybeans was evaluated in the case of the operation speed of 0.18-0.28 m/s. The performance demonstrated a rate of 320-500 ㎡/h, 260-400 ㎡/h, and 210-330 ㎡/h for the 0.20 m, 0.25 m, and 0.30 m soybean planting density, respectively. One hundred percent punching capacity was confirmed in 30 mm distance between the ground and the blade. Additionally, in the 50 mm distance condition, the performance of round, square, and hexagonal blades were observed in the range of 16.7-25.2%, 33.0-42.3%, and 54.5-100.0%, respectively. Above all, the hexagonal blade with a 60° edge angle had the most superior cutting quality demonstrating a smooth and soft cutting plane of the plastic.

• 월간 기계설비
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• s.226
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• pp.60-63
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• 2009

안전, 또 안전!은 아무리 강조해도 지나치지 않다. 한때 우리나라는 '안전불감증'이라 해도 과언이 아닐만큼 안전에 대한 의식이 저조해서 사고가 많았다. 이에 따라 각 건설현장에서는 안전에 대한 교육을 철저히 시키고 행동강령 주지 등 많은 노력을 기울여 왔다. 특히 가스와 관련한 사고는 대형사고로 번질 가능성이 높기 때문에 작업 시 더욱 주의를 필요로 한다. 본지는 가스시공 시의 일반적인 안전수칙과 탱크, 용기, 기계실, 고소작업, 용접작업 천공 분기작업, 도시가스 공급시설물 작업 시의 안전수칙에 대하여 게재한다.

• Explosives and Blasting
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• v.29 no.1
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• pp.17-26
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• 2011

In this study, the pollutants contained in water and soil samples taken from the explosive demolition site were examined to investigate the effects on environment, and management plan of non-point source pollution in the demolition site was suggested through characterizing the movement of the pollutant with time. As results, pH value of the water and soil samples after the demolition work was 8.5~9.3 which exceeds the Korean environmental criterion of water and soil range due to calcium hydroxide compounds in the concrete. The concentration level of heavy metals caused by the explosive demolition doesn't exceed the environmental criterion of water and soil doesn't exceed the environmental criterion of water and soil quality, and the influence of water and soil pollution on the environment was not considered. The concentration of the heavy metals was analyzed and that of Cr, Cu, Zn and Hg among the heavy metals increased after the drilling and explosive demolition. This says that concentration of the heavy metals during explosive demolition works needs to be monitored. The most pollutants with time or rain dilution into the demolition site decreased and this means that the pollutants caused by the explosive demolition might have influenced to vicinity of the demolition sites as non-point pollution.