• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.434-437
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• 2006

Though numerous drilling has been performed in Jeju Island for development of ground water, the wells are mostly located along the coast lines or at low altitude area, and can hardly be found on the mid-mountain area. Two-dimensional magnetotelluric (MT) surveys have been carried out to cover the lack of geological Informal ion on the mid-mountain area and to figure out any possible structures or evidences for deep geothermal energy remained. Two-dimensional (2-D) inversion of MT data for four survey lines surrounding the Halla mountain show a thick layer having around 10 ohm-m in the depth of a few hundred meters throughout the survey area, which can be considered as the unconsol idated sedimentary layer. And they also show a conductive anomaly extending to more than 2km depth at the central part of each survey lines, which can possibly be related with old volcanic activities during the formation of Halla Mt.. Further seological/geophysical investigations should be followed.

• Journal of Korean Institute of Industrial Engineers
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• v.39 no.3
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• pp.149-155
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• 2013

Electric discharging machining (EDM) is commonly adopted to machine the precise and tiny part when it is difficult to meet the productivity and the tolerance by the conventional cutting method. The die-sinking EDM method works well to machine the micro-parts and the perpendicular wall of die and mould, whereas EDM drilling, called super drill, is excellent to machine the deep and narrow hole regardless the material hardness and the hole location. However, the electrode wear is rapid compared to the conventional cutting tool and makes it difficult to control the electrode feeding and to machine precisely. This paper presents an efficient method to estimate the electrode wear using hole pass-through experiment while the stochastic method is used to compensate for the estimation model. To validate the proposed method, the commercial EDM drill machine is used. The experiment result shows that the electrode wear amount can be predicted very precisely.

• Journal of Korean Neurosurgical Society
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• v.65 no.3
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• pp.479-488
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• 2022

Objective : The surgical management of trigeminal neuralgia (TN) caused by petrous apex meningioma (PAM) is still a challenge because of the lesion's deep location and the surrounding complex structures. The authors describe the intradural anterior transpetrosal approach (ATPA) and its effect on the treatment of TN secondary to PAM. Methods : A retrospective analysis of 15 patients with TN secondary to PAM who underwent surgery via the intradural ATPA was conducted. The key techniques, which included drilling off the petrosal apex (PA) and opening the upper wall of Meckel's cave (MC), are described in detail. Results : Total removal of the tumor and complete pain relief (Barrow Neurological Institute I) were achieved in all 15 patients without significant morbidity. Five patients developed new facial numbness postoperatively, which disappeared within three months after surgery. The postoperative magnetic resonance imaging showed temporal lobe swelling in three patients, but no clinical symptoms. One patient had cerebrospinal fluid leakage and was managed with bed rest and temporary lumbar drainage. One patient had an intracranial infection and was treated with antibiotics. By the last follow up, no patients had pain relapse or/and tumor recurrence. It is worth noting that the vascular compression at the root of the trigeminal nerve was found in one patient during the operation. Conclusion : Our experience suggests that drilling off the PA and opening the upper wall of the MC are key elements for a good outcome of the treatment of TN secondary to PAM. The intradural ATPA has the advantages for both tumor resection and pain relief.

• Geophysics and Geophysical Exploration
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• v.11 no.3
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• pp.204-213
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• 2008

This paper presents the analysis about the stability of the Pohang deep geothermal borehole drilled in 2006. Severe wellhole instability problems such as collapse and tight hole occurred in weak rocks while drilling. Optimal mud pressure (mud window) required to prevent instability problems during drilling is obtained from analysis on in-situ stress and rock strength. The window is bounded by vertical stress in its upper limit and by either collapse pressure or pore pressure in its lower limit. Mud window varies with different types of rocks. In the top-most semi-consolidated mudstone formation, no mud window can secure borehole stability. In some weak rock types (basic dyke and crystal tuff), the borehole pressure needs to be higher by $50{\sim}60%$ than hydrostatic pressure. That means a mud density of 1.5 g/$cm^3$ or higher should be applied during drilling in order to prevent excessive collapse around the borehole.

• Water for future
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• v.14 no.4
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• pp.73-81
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• 1981

More than 650 numbers of water well ranging in depth from 100M to 200M were installed in South Korean Penninsula during the last decade for the purpose of industrial use and municipal water supply. Those data were compiled and synthesized by writer to determine their hydrogeologic occurences in accordance with their geologic and areal characteristics. Rocks yielding the deep seated ground water beared in the geologic primary and secondary porosities are classified into 6 groups according to their geologic, hydrogeologic, and topographic characteristics, that are: volcanic, sedimentary, meta-sediment and/or schist, andesitic, gneissic, and granitic rocks. The order of ground water productivity of the groups is as written above. Even granitic rocks including porphyries, granite, and intermediate and basic plutonic rocks is considered to be the most poorest ground water yielding group among 6, it's average yield form a single well with average drilling depth of 116M is about 225 cubic meters per day if it's drilling site is properly located. Generally speaking, seizable geologic structures such as fractured, sheared, and faulted zone at the flat surface and valley center yield almost 310% more of deep seated bet rock ground water in comparision with minor structures of joints, bedding planes, and so on that are occured at high land. 50 numbers of water well drilled at crystalline rocks were specially checked and measured it's ground water yie 1ds at each drilled depth to determine each interval's productivity while hammer drilling was going on. The results indicate that the specific capacity and yield of each water well at a depth below 70M to 80M was almost neglegible. It means that optimum well depth of crystalline rocks, except the area having seizable geologic structures, shall be not deeper than 80M.

• Journal of the Korean Geosynthetics Society
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• v.21 no.2
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• pp.21-30
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• 2022

Shear strength is the most important indicator in the evaluation of rock slope stability. It is generally estimated by comparing the results of existing literature data, back analysis, experiments and etc. There are additional variables related to the state of discontinuity to consider in the shear strength of the rock slope. It is difficult to determine whether these variables exist through drilling, and it is also difficult to find an exact relationship with shear strength. In this study, the data calculated through back analysis were used. The relationship between previously considered variables was applied to deep learning and the possibility for estimating shear strength of rock slope was explored. For comparison, an existing simple linear regression model and a deep learning algorithm, a deep neural network(DNN) model, were used. Although each analysis model derived similar prediction results, the explanatory power of DNN was improved with a small differences.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.4
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• pp.491-505
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• 2018

As an alternative to deep geological disposal technology, which is considered as a reference concept, the domestic applicability of deep borehole disposal technology for high level radioactive waste, including spent fuel, has been preliminarily evaluated. Usually, the environment of deep borehole disposal, at a depth of 3 to 5 km, has more stable geological and geo-hydrological conditions. For this purpose, the characteristics of rock distribution in the domestic area were analyzed and drilling and investigation technologies for deep boreholes with large diameter were evaluated. Based on the results of these analyses, design criteria and requirements for the deep borehole disposal system were reviewed, and preliminary reference concept for a deep borehole disposal system, including disposal container and sealing system meeting the criteria and requirements, was developed. Subsequently, various performance assessments, including thermal stability analysis of the system and simulation of the disposal process, were performed in a 3D graphic disposal environment. With these analysis results, the preliminary evaluation of the domestic applicability of the deep borehole disposal system was performed from various points of view. In summary, due to disposal depth and simplicity, the deep borehole disposal system should bring many safety and economic benefits. However, to reduce uncertainty and to obtain the assent of the regulatory authority, an in-situ demonstration of this technology should be carried out. The current results can be used as input to establish a national high-level radioactive waste management policy. In addition, they may be provided as basic information necessary for stakeholders interested in deep borehole disposal technology.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.5
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• pp.8-17
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• 2016

While greenhouses have been utilized as a sustainable alternative to traditional soil farming, they are often powered by diesel boilers that necessitate vast amounts of non-renewable energy and emit toxic fumes. Thus, geothermal heat pumps have been proposed as a more energy-efficient substitution for diesel boilers. Currently, most horticultural facilities in the United States use shallow geothermal systems, and are often equipped with horizontal underground heat exchangers as well as heat pump equipment. These shallow geothermal systems require a large drilling site and heat pump to function, which results in high maintenance costs. The heat pump itself consumes a large amount of power, which degrades system performance. Conversely, high temperatures can be attained within a single borehole in deep geothermal vertical closing systems without using a heat pump. This setup can dramatically reduce the power consumption and improve system performance. In this study, we have modeled a circulation simulator after the circulation systems in deep geothermal facilities to analyze a 2000-meter borehole in Naju-Sanpo-myeon. The simulator is operated by manipulating various putative parameters affecting system performance to analyze the system's coefficient of performance.

• Journal of Microbiology and Biotechnology
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• v.18 no.1
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• pp.5-14
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• 2008

The deep subseafloor rock in oil reservoirs represents a unique environment in which a high oil contamination and a very low biomass can be observed. Sampling this environment has been a challenge owing to the techniques used for drilling and coring. In this study, the facilities developed by the Brazilian oil company PETROBRAS for accessing deep subsurface oil reservoirs were used to obtain rock samples at 2,822-2,828 m below the ocean floor surface from a virgin field located in the Atlantic Ocean, Rio de Janeiro. To address the bacterial diversity of these rock samples, PCR amplicons were obtained using the DNA from four core sections and universal primers for 16S rRNA and for APS reductase (aps) genes. Clone libraries were generated from these PCR fragments and 87 clones were sequenced. The phylogenetic analyses of the 16S rDNA clone libraries showed a wide distribution of types in the domain bacteria in the four core samples, and the majority of the clones were identified as belonging to Betaproteobacteria. The sulfate-reducing bacteria community could only be amplified by PCR in one sample, and all clones were identified as belonging to Gammaproteobacteria. For the first time, the bacterial community was assessed in such a deep subsurface environment.

• Journal of the Korean Geophysical Society
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• v.7 no.2
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• pp.113-120
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• 2004

Hydrochemical characteristics of deep groundwater at Surak-ri, Nonsan-gun, Chungnam Province was explained by major ion concentration, water type, and phase stability diagram. The area is composed of meta-sedimentary rock and quartz pophyry. The 5 boreholes where deep groundwater was sampled and analyzed are located on the meta-sedimentary rocks and drilling depth range of the wells is from 554 m to 928 m. pH, TDS, Na, and SiO2 values are high in the groundwater from meta-sedimentary area intruded by quartz pophyry, while Ca is high in the groundwater from meta-sedimentary area. K and Mg concentrations are low but F concentration is high both groundwater. The content of major anions is in the order of CO3(HCO3)>Cl>SO4(F) in both geology, while that of major cations shows the order of Na>Ca>K(Mg) in meta-sedimentary area intruded by quartz porphyry and a>Na>Mg>Na in meta-sedimentary area. Based on the phase equilibrium in the systems Na2O-Al2O3-SiO2-H2O and K2O-Al2O3-SiO2-H2O, the groundwater is saturated with respect to Quartz and more evolved compared with the natural mineral water. It is concluded that chemical evolution in the groundwater from meta-sedimentary area intruded by quartz porphyry, is nearly saturated with respect to feldspar, while the groundwater from meta-sedimentary area continue to proceed with increasing pH by reaction of feldspar.