• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.6
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• pp.90-96
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• 1998

The ductile cast iron is austempered at 300, 350 and 40$0^{\circ}C$ temperature in order to investigate the basic factors for monitoring drill wear in automatic production process, and cutting force and AE RMS signals are measured with changing cutting condition for ADI(Austempered Ductile Cast Iron) with different mechanical properties. The signals of cutting force were influenced by cutting speed and feedrate greatly. On the other hand AE RMS signals are influenced by cutting speed where as it is not related with feedrate. As the depth of drilling increases, cutting force shows a slow increase and the value of AE RMS increases until the range of h/d=4. But over the range it increases greatly due to an amount of chip discharge and friction with inner wall of drilling hole, etc. As the drill diameter increases at a constant depth of drilling. Cutting force increases linearly, but the level of AE RMS does not increases linearly due to circumferential velocity and great influence of h/d.

• Economic and Environmental Geology
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• v.49 no.6
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• pp.479-490
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• 2016

Seabed drilling system has recently been used to drill seafloor mineral resources. This case report highlights the procedure and result of sea-trial of seabed drilling system at off-shore of Japan on March, 2016 as well as briefs an international-technical trend of seabed drilling system. In case of having less than 100 m drill depth, seabed drilling system is favorable for seafloor mineral deposits which are mostly distributed within a narrow district and situated between 1000~3000 m water depth, compared with vessel-mounted drilling system. The system is featured by the remotely-operated drill gear, which has top drives, drill strings and mud system on it. The core samples are generally recovered to ship with seabed driller after a dive. In this sea-trail, recovery rate of core samples averagely shows about 55% and the recovered rocks mostly correspond to fresh and/or weak-altered basalt. In case of drilling hydrothermal ore deposit, the recovery rate would be lower than 55% because of the fragile nature of ores. Alternatively it is used to collect cutting chips through riser or bins in order to increase the recovery rates. Recently a reverse circulation method is taken considered to acquire the better cutting-chips. Three-leg type outrigger system and four-leg type leveling system are the competing landing-instruments of seabed drill system. However the landing efficiency using these gears has to be further monitored due to lack of case reports.

• Economic and Environmental Geology
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• v.49 no.1
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• pp.63-75
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• 2016

The ratio of fractured reservoir is very high in oil & gas fields around the world. The demand of drilling technology for fractured reservoir is expected to increase continuously if oil and gas prices are economical. The purpose of the review study is to help operator or driller in selecting of proper drilling technology for preventing a lost circulation in the fractured formation. In order to achieve this goal, fractured reservoir(formation) they are classified into partial lost circulation formation and total lost circulation formation. In case of partial lost circulation formation, the drilling problem can be solved by using LCM(lost circulation material) mud additive and squeezing cement. For shallow depth, total lost circulation formation can be drilled safely and economically with casing drilling method. Also, for deeper depth, problems of total lost circulation in formation can be solved by applying mud cap, which is one of the drilling methods. This was confirmed through field application such as Italy's Medusa-1 field and Qatar's North field.

• Tunnel and Underground Space
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• v.16 no.4 s.63
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• pp.347-356
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• 2006

We analyzed case studies doing in-depth inspection of tunnel to maintain safety of existing tunnel in constructing new tunnel near to a existing tunnel with single track. Futhermore, We accomplished in-depth inspection of existing tunnel and numerical analysis. We suggested remedies to security safety of existing tunnel. We applied line drilling and pre-large hole boring method not to have an effect on existing tunnel and convinced the safety of existing tunnel from blast-vibration and blast-noise of numerical analysis. We planed to install basset system to measure displacement of existing tunnel according to excavating new tunnel.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.8
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• pp.96-106
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• 2001

As the drilling depth increases, the cutting torque increases and fluctuates, which can lead to the machine tool vibration, severe tool wear, and catastrophic tool breakage. Hence, cutting torque control is very important to improve productivity in drilling. In this paper, a PID controller was designed to control the drilling torque. The plant including the feed drive system, cutting process and spindle drive system was modeled for controller design. The Ziegler-Nichols method was used to determine the controller gain and control action times and the root locus plot was used to tune the controller gain for a certain cutting condition. Also, suggested was a simple method to obtain the tuned controller gain for an arbitrary cutting condition not using the Ziegler-Nichols method and the root locus plot. The performance of the designed controller and the effect of controller gain tuning were verified from experiments.

• Journal of the Korean Geosynthetics Society
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• v.15 no.4
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• pp.53-62
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• 2016

This paper presents the results of a reduced-scale physical model investigation into the effect of drilling fluid with different mix designs for use in offshore bore hole collapse prevention. Compare the bentonite and Attapulgite use. Reduced-scale model tests were then carried out considering field procedures for cases with decomposed granitic soil with fines and a sand with various drilling fluids with different mix designs. The results were indicated that the addition of polymer to the bentonite based drilling fluid decreases the amount of injected drilling fluid and increases the final depth of excavation. Also revealed that the effect of polymer on the performance of drilling fluid is more pronounced in the decomposed granite soil with fines than sand. Practical implications of the findings from this study are discussed in detail.

• Journal of the Korean Society for Precision Engineering
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• v.6 no.3
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• pp.24-31
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• 1989

By use of the machining center, step-feed drilling was operated under the variety of conditions as to materials, tools and cutting conditions. Based on this study the following conclusions can be drawn : 1) The cutting force can be diminished by utilizing the step-feed working; specially the most effective was it for the brass among the carbon steel, the brass, and the cast iron. 2) Tool life can be enlarged more than double when three-step-feed working is used. 3) For the constant cutting-depth(30mm), the most optimal number of stepping is 3.

• Tunnel and Underground Space
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• v.25 no.6
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• pp.534-542
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• 2015

Round trip activity occurs discretely due to the abrasion of drill bit in the deep drilling project. Round trip has great impact on the drilling performance because it takes more time to change a drill bit as the depth goes deeper. Therefore, a reliable prediction technology of the round trip should be secured for feasibility analysis and effective management of the drilling project. Lee et al. (2013) developed the TOSA (round trip occurrence simulation algorithm) which can analyze the depth and timing of round trip occurrence at each abrasion state of bit. However, TOSA has weakness that it takes long time for simulation because the number of simulation increase exponentially as increasing the number of simulation section. This study developed the TOSA based round trip performance prediction module using genetic algorithm for simulating in a short time and verified simulation results.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.361-364
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• 2002

This paper discusses the influencing factors such as coring position, height to diameter ratio of core specimen(h/d) and coring torque on the strength estimation of concrete by small site coring method in order to verify the validities of small size core method. According to results, as for the influence of drilling position, when core specimens are obtained from the place parallel to placing direction, compressive strength of core specimens are higher than those perpendicular to placing direction. This is due to the loss of the area of core specimen perpendicular to plating direction by bleeding. And in case of $\phi$ 24mm core specimen, when vertical drilling against placing direction is taken. compressive strength of core specimen obtained at the bottom of the structure is higher than that at the top of the structure. As for the influence of height to depth ratio, as h/d ratio increases compressive strength shows to be decreased. As for the influences of rotation speed of drilling machine, as its speed goes up, compressive strength decreases, regardless of core diameter.

• Explosives and Blasting
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• v.8 no.4
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• pp.3-22
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• 1990

The $\varphi{4.5}$ meters pilot tunneling work is almost done to the $\varphi{11.3}$ meters twin tunnel of NAM SAN No1. The south side pit of 400 meters is weak zone of Rock status, so client request us to allow the cautious blasting pattern for drilling on the condition of 0.2 kine vibration allowance limited for the safety of side running tunnel. The pattern of cautious blasting carried out by 6 time divided fiving on the round drilling depth of 1.20 meters(1.10) and also applied control blasting method with line drilling due to the reduction of vibration.