• Geomechanics and Engineering
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• 제18권2호
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• pp.215-224
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• 2019

Excavation of long tunnels by shielded TBMs is a safe, fast, and efficient method of tunneling that mitigates many risks related to ground conditions. However, long-distance tunneling in great depth through adverse geological conditions brings about limitations in the application of TBMs. Among various harsh geological conditions, squeezing ground as a consequence of tunnel wall and face convergence could lead to cluttered blocking, shield jamming and in some cases failure in the support system. These issues or a combination of them could seriously hinder the performance of TBMs. The technique of excavation has a strong influence on the tunnel response when it is excavated under squeezing conditions. The Golab water conveyance tunnel was excavated by a double-shield TBM. This tunnel passes mainly through metamorphic weak rocks with up to 650 m overburden. These metamorphic rocks (Shales, Slates, Phyllites and Schists) together with some fault zones are incapable of sustaining high tangential stresses. Prediction of the convergence, estimation of the creeping effects and presenting strategies to overcome the squeezing ground are regarded as challenging tasks for the tunneling engineer. In this paper, the squeezing potential of the rock mass is investigated in specific regions by dint of numerical and analytical methods. Subsequently, several operational solutions which were conducted to counteract the challenges are explained in detail.

• JSTS:Journal of Semiconductor Technology and Science
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• 제14권5호
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• pp.572-578
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• 2014

In order to overcome small current drivability of a tunneling field-effect transistor (TFET), a TFET using Schottky barrier (SBTFET) is proposed. The proposed device has a metal source region unlike the conventional TFET. In addition, dopant segregation technology between the source and channel region is applied to reduce tunneling resistance. For TFET fabrication, spacer technique is adopted to enable self-aligned process because the SBTFET consists of source and drain with different types. Also the control device which has a doped source region is made to compare the electrical characteristics with those of the SBTFET. From the measured results, the SBTFET shows better on/off switching property than the control device. The observed drive current is larger than those of the previously reported TFET. Also, short-channel effects (SCEs) are investigated through the comparison of electrical characteristics between the long- and short-channel SBTFET.

• Archives of Reconstructive Microsurgery
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• 제25권1호
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• pp.1-6
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• 2016

Purpose: The external ear is a common area of trauma on the body prone to exposure of ultraviolet light, which can lead to skin cancer. Thus, variable techniques have been developed and used for reconstruction of the external ear. The aim of this study is to review the surgical method, its area of application, as well as advantages and pitfalls of reconstruction of the external ear with inferior based retroauricular flaps. Materials and Methods: Eight patients underwent external ear reconstruction with inferior based retroauricular flap for external ear defects in our institute from September 2012 to June 2015. According to the area of the defect, patients were classified as middle 1/3 (n=4), inferior 1/3 (n=2), superior auroculo-cephalic sulcus (n=1), and external auditory canal (n=1). Results: All of the flaps survived the operation and there was no marginal necrosis. Mean size of the defect was $2.8{\times}1.8cm$ and mean size of the retroauricular flap was $5{\times}2cm$. For insetting of the flap, a subcutaneous tunneling technique was used in 6 cases and rotation without subcutaneous tunneling was used in 2 cases. Transient paresthesia occurred in 3 cases. Two cases recovered within 3 months but one case did not recover until 6 months. Conclusion: The inferior based retroauricular flap is an available technique in external ear reconstruction with one stage operation.

• 지질공학
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• 제6권3호
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• pp.111-118
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• 1996

터널이 굴진될 때 주변지반은 3차원적으로 거동하게 되나 설계단계에서의 해석은 일반적으로 2차원적으로 수향하고 있다. 2차원적인 터널해석은 응력분배법 또는 강송 변화법에 의하여 3차원적인 터널굴진에 따른 다양한 조건하에서의 정규화된 지반 변위곡선을 구하고 이 곡선과 유사한 곡선이 유도되도록 시행착오법에 의하여 2차원 해석을 실시하므로 3차원 해석과 근사한 변위곡선을 가지도록 막장거리별 응력분배비율을 결정하였다. 따라서, 시간과 노력이 많이 소요되는 3차원 해석없이도 적절한 응력분배비율을 적용하는 경우 2차원 해석으로 터널굴진시의 3차원적인 지반거동을 평가할 수 있게 되었다.

• Geomechanics and Engineering
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• 제20권6호
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• pp.475-484
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• 2020

The prediction of the ground conditions ahead of a tunnel face is very important, especially for tunnel boring machine (TBM) tunneling, because encountering unexpected anomalies during tunnel excavation can cause a considerable loss of time and money. Several prediction techniques, such as BEAM, TSP, and GPR, have been suggested. However, these methods have various shortcomings, such as low accuracy and low resolution. Most studies on electrical resistivity tomography surveys have been conducted using numerical simulation programs, but laboratory experiments were just a few. Furthermore, most studies of scaled model tests on electrical resistivity tomography were conducted only on the ground surface, which is a different environment as compared to that of mechanized tunneling. This study performed a laboratory experimental test to extend and verify a prediction method proposed by Lee et al., which used electrical resistivity tomography to predict the ground conditions ahead of a tunnel face in TBM tunneling environments. The results showed that the modified dipole-dipole array is better than the other arrays in terms of predicting the location and shape of the anomalies ahead of the tunnel face. Having longer upper and lower borehole lengths led to better accuracy of the survey. However, the number and length of boreholes should be properly controlled according to the field environments in practice. Finally, a modified and verified technique to predict the ground conditions ahead of a tunnel face during TBM tunneling is proposed.

• 한국터널지하공간학회 논문집
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• 제7권1호
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• pp.89-96
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• 2005

사회 전반에 걸친 디지털 혁명에 따라 IT를 기반으로 하는 다양한 정보화 터널시공기법이 개발되고 있으며 터널시공시 의사결정체계의 일환으로 적용되고 있다. 따라서 본 연구에서는 PDA를 이용한 터널시공의 정보화에 대하여 기술하였으며, 특히 시공중 발생하는 각종 막장면 데이터를 실시간으로 입 출력 및 저장하고 이를 기반으로 지보패턴을 결정할 수 있는 의사결정체계를 구축하였다. 이를 위하여 무선 네트워크, 이동식 컴퓨터, CDMA 및 디지털카메라 등 최근 정보통신을 바탕으로 한 막장면 매핑자료의 실시간 데이터 수집 및 해석, 디지털 매핑등이 가능한 PDA용 S/W를 개발하였으며 현장적용에 대하여 고려하였다. 향후에는 실제 시공시 사용된 지보방법 및 소요 지보량을 함께 저장할 수 있는 DB를 구축하는 한편 현장적용을 통한 feedback 결과에 대하여 연구가 지속될 예정이다.

• 지질공학
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• 제16권3호
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• pp.265-273
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• 2006

터널 시공 시에 관찰되는 막장의 상태는 굴착예정 막장의 지질상태를 가장 잘 표현하며, 지보패턴의 결정에 큰 영향을 미치므로 막장지질조사는 매우 중요하다. 따라서 막장지질조사를 통해서 단순히 암반평가만을 수행하는 것이 아니라 터널 시공 중에 영향을 미칠 수 있는 모든 지질요소 등을 관찰하여 다음 시공 막장의 지반상태를 예측하여야 한다. 그러나 현재 막장지질조사 시 기술 및 경험, 시간적인 제약 등으로 인한 한계로 조사결과를 시공에 충분히 반영하지 못하는 것이 현실이다. 본 연구에서는 기 시공된 국내 터널의 막장관찰기록지의 기록상황을 집계하여 막장지질조사의 문제점을 분석하고 그 개선 방안을 제시하였다

• Journal of Gastric Cancer
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• 제13권4호
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• pp.199-206
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• 2013

Since the first transgastric natural orifice transluminal endoscopic surgery was described, various applications and modified procedures have been investigated. Transgastric natural orifice transluminal endoscopic surgery for periotoneoscopy, cholecystectomy, and appendectomy all seem viable in humans, but additional studies are required to demonstrate their benefits and roles in clinical practice. The submucosal tunneling method enhances the safety of peritoneal access and gastric closure and minimizes the risk of intraperitoneal leakage of gastric air and juice. Submucosal tunneling involves submucosal tumor resection and peroral endoscopic myotomy. Peroral endoscopic myotomy is a safe and effective treatment option for achalasia, and the most promising natural orifice transluminal endoscopic surgery procedure. Endoscopic full-thickness resection is a rapidly developing natural orifice transluminal endoscopic surgery procedure for the upper gastrointestinal tract and can be performed with a hybrid natural orifice transluminal endoscopic surgery technique (combining a laparoscopic approach) to overcome some limitations of pure natural orifice transluminal endoscopic surgery. Studies to identify the most appropriate role of endoscopic full-thickness resection are anticipated. In this article, I review the procedures of natural orifice transluminal endoscopic surgery associated with the upper gastrointestinal tract.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1324-1334
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• 2005

This study investigated the applicability of the Artificial Neural Network (ANN) technique for prediction of tunnel behavior. For training data collection, a series of finite element analyses were conducted for actual tunnel project site. Using the data, optimimzed ANNs were developed through a sensitivity study on internal parameters. The developed ANNs can make tunneling related predictions such as tunnel crown settlement, shotcrete lining stress, ground surface settlement, and groundwater inflow rate. The results indicated that the developed ANNs can be used as an effective and efficient tool for tunnelling related prediction in practical tunneling situations.

• 한국터널공학회:학술대회논문집
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• 한국터널공학회 2005년도 학술발표회 논문집
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• pp.105-116
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• 2005

This study investigated the applicability of the Artificial Neural Network(ANN) technique for prediction of tunnel behavior. For training data collection, a series of finite element analyses were conducted for actual tunnel project site. Using the data, optimimzed ANNs were developed through a sensitivity study on internal parameters. The developed ANNs can make tunneling related predictions such as tunnel crown settlement, shotcrete lining stress, ground surface settlement, and groundwater inflow rate. The results indicated that the developed ANNs can be used as an effective and efficient tool for tunnelling related prediction in practical tunneling situations.