Differential settlement and soil dynamic stress of a culvert-embankment transition zone due to an adjacent shield tunnel construction

Yao Shan,Shunhua Zhou,Yao Shu 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.7

The effects of shield tunnel construction on the differential settlement and the distribution of soil dynamic stress of an adjacentculvert-embankment transition zone are investigated. A construction project of shield tunnels in Hangzhou (China) beneath anexisting railroad culvert-embankment transition zone is employed as a case study. Firstly, the shield tunneling activities in the vicinityof a culvert-embankment transition zone are simulated by a three-dimensional (3D) Finite Element Analysis (FEA) method. Thedifferential settlement of the transition zone is calculated to evaluate the influence of the shield tunneling on the safety of the passingtrain. Secondly, a plane strain model is employed to investigate the discipline of the soil dynamic stress in transition zones, which isinduced by the passing train and the shield tunnel beneath the railroad. Results indicate that the reinforcement treatment of thefoundation is required since the embankment differential settlement is significantly affected by the shield tunneling. Finally, arecommended treatment is introduced according to the property of the surrounding soil. Numerical simulation reveals that thistreatment is appropriate for reducing the differential settlement and soil dynamic stress of the transition zone.

매개변수 분석을 통한 단층파쇄대의 소단면 쉴드 TBM 터널 굴착 시 최적 보강영역 연구

강병윤,박형근,차재훈,김영진 사단법인 한국터널지하공간학회 2020 한국터널지하공간학회논문집 Vol.22 No.3

When excavating a small cross-section tunnel in a fault fracture zone using the shield TBM method, there is a high possibility of excessive convergence and collapse.Appropriate ground reinforcement is required to minimize construction cost loss andtrouble due to a fault fracture zone. In this study, the optimal reinforcement area was suggested and the surrounding ground behavior was investigated through numerical analysis using MIDAS GTS NX (Ver. 280). For the parameters, the width of the fault fracture zone, the existence of fault gouge, and the groundwater level and depth of cover were applied. As a result, when there is not fault gouge, the convergence and ground settlement are satisfied the standard when applying ground reinforcement by up to 0.5D. And, due to the high permeability coefficient, it is judged that it is necessary to apply 0.5D reinforcement. There is a fault gouge, it was possible to secure stability when applying ground reinforcement between the entire fault fracture zone from the top of the tunnel to 0.5D. And, because the groundwater discharge occurred within the standard value due to the fault gouge, reinforcement was unnecessary. 쉴드 TBM 공법을 사용해 단층파쇄대에 소단면 공동구 터널을 굴착 시 과다한 내공변위 및 붕락 발생 가능성이 높다. 단층파쇄대로 인한 트러블 및 공기증가로 인한 공사비 손실을 최소화하기 위해 적절한 지반보강이 요구된다. 본 연구에서는단층파쇄대의 폭, 단층점토의 존재여부, 토피고 지하수위를 매개변수로 하여 MIDAS GTS NX (Ver. 280)을 이용한 수치해석을 통해 최적보강영역을 제시하고 주변지반 거동을 알아보았다. 그 결과 단층점토가 없는 경우 최대 0.5D 만큼 지반보강 적용 시 내공변위 및 지표침하 기준을 만족하였으며, 높은 투수계수로 인해 0.5D의 차수보강 적용이 필요하다고 판단된다. 단층점토가 존재할 때 내공변위 및 지표침하는 최소 0.5D에서 최대 터널 상부 단층파쇄대 전체에 지반보강 적용 시 안정성확보가 가능하였으며, 단층점토로 인해 지하수 유출량이 기준치 이내로 발생하여 차수보강이 불필요하였다.

건물 산란계수를 이용한 비가시거리 영역에서의 전파환경

홍성욱,강부식,김흥수 濟州大學校 産業技術硏究所 1997 산업기술연구소논문집 Vol.8 No.1

In this paper, the scattered electric fields is computed to predict the shielding zone by analysing the effect of the reflected azimuth anlge at the building, and considering the path differences at observation point between the rays from origin and any point in the building. The scattering coefficients. which are applicable to the prediction of shielding zone. are computed and compared with measured one. We found that the scattering power become weak over 10 degree of the azimuth angle at which the scattering coefficient is lower than 40 dB. From this, the shielding zone can be estimated.

선박 해수배관에서 용접봉의 종류에 따라 직류 아크 용접한 용접부위의 부식특성에 관한 전기화학적 평가

이성열(Sung-Yul Lee),이규환(Kyu-Hwan Lee),원창욱(Chang-uk Won),나승수(Shane Na),윤영곤(Young-Gon Yoon),김윤해(Yun-Hae Kim),이명훈(Myeong-Hoon Lee),문경만(Kyung-Man Moon),김진경(Jin-Gyeong Kim) 한국해양공학회 2013 韓國海洋工學會誌 Vol.27 No.3

The seawater pipes in the engine rooms of ships are surrounded by severely corrosive environments caused by fast flowing seawater containing chloride ions, high conductivity, etc. Therefore, it has been reported that seawater leakage often occurs at a seawater pipe because of local corrosion. In addition, the leakage area is usually welded using shielded metal arc welding with various electrodes. In this study, when seawater pipes were welded with four types of electrodes(E4311, E4301, E4313, and E4316), the difference between the corrosion resistance values in their welding zones was investigated using an electrochemical method. Although the corrosion potential of a weld metal zone welded with the E4316 electrode showed the lowest value compared to the other electrodes, its corrosion resistance exhibited the best value compared to the other electrodes. In addition, a heat affected zone welded with the E4316 electrode also appeared to have the best corrosion resistance among the electrodes. Furthermore, the corrosion resistance of the weld metal zone and heat affected zone exhibited relatively better properties than that of the base metal zone in all of the cases welded with the four types of electrodes. Furthermore, the hardness values of all the weld metal zones were higher than the base metal zone.

HT 후판강재의 용접 열영향부(HAZ)에서 발생하는 용접균열의 민감도에 관한 고찰

안현모(Hyun-Mo Ann),이종식(Jong-Sik Lee) 산업기술교육훈련학회 2012 산업기술연구논문지 (JITR) Vol.17 No.1

The welding crack susceptibility around of heat affected zone in welded thick(HT80 steel) joint is very important, and especially the welded structure for industrial structure such as plant, shipping, bulding, car parts welding is needed various welding method. In joining method of welding structure, welding residual stresses inevitably occur welded joints after welding, the evaluation of welding cracking susceptibility in HT80 steel was performed using thermally simulated heat affected zones. So, this paper deals with investigations into the testing of electric shield metal arc welding(SMAW) process that is frequently in welding HT80 steel that are quenched and tempered after welding. It has been carried out to study the weldability using test of welded specimen in welding cracking of HT80 steel that frequently occur after reheating. Also, are selected for examining the mechanism of welding crack-occurrence and way to reliability in cracking of the welded metal. This examinations were carried out in terms of micro-structural characterization, micro-hardness measurement and welded bend test. It was found that welding cracking susceptibility increased as hardness increased and cooling speed of weld heat cycle, Cooling curve Diagram HT80 steel shows what can be prevented in the weld metal and heat-affected zone when be controlled by hardness value in heat treatment from 800℃ to 500℃, and welding crack susceptibility of HT80 is not occur when bead pass below about multi 10 pass. It evident that welding cracking susceptibility can be eliminated or reduced by controlling the welding parameters such as the realation of cooling cycly, max. hardness value in HAZ, affect of residual stress according to reheating cycle or In view of the results, welding crack is not occur below about 490MPa(50kgf/mm2) in reinforcement and welding pass is below about 10 pass. For the improving of Welding crack can be controlled of various parameters(decrease of HAZ hardness, stress-relief in HAZ, micro-structural characterization, cooling cycle, etc.) in welding.

용접 재료 별 해수 배관 용접부위의 부식 특성에 관한 전기화학적 평가

김진경(JIN-GYEONG KIM),원창욱(CHANG-UK WON),조황래(HWANG-RAE JO),이명훈(MYUNG-HOON LEE),김윤해(YUN-HAE KIM),문경만(KYUNG-MAN MOON) 한국해양공학회 2007 韓國海洋工學會誌 Vol.21 No.5

The sea water pipe of a ship's engine room is a severely corrosive environment caused by fast flawing sea water containing chloride ions and high conductivity. Therefore, leaking of sea water may occur as a result of local corrosion of the welded zone. Leaking is usually controlled by various welding methods. In this study, when the sea water pipe is welded with certain welding methods and welding electrodes, the corrosion resistance of WM (Welding metal) and HAZ (Heat affected zone) was investigated using electrochemical methods. Although the corrosion potential of the HAZ is higher than that of WM, the corrosion resistance of WM is superior to HAZ. However, when WM and HAZ are both opened to the sea water, the WM part with the anode was more seriously corroded than was the HAZ of the cathode by performance of a galvanic cell due to difference of the corrosion potential between HAZ and WM, In particular TIG welding showed relatively good results in corrosion resistance of both HAZ and WM compared to other welding methods.

건물 산란계수를 이용한 비가시거리영역에서의 전파환경

강부식,김홍수,홍성욱 濟州大學校工科大學産業技術硏究所 1997 尖端技術硏究所論文集 Vol.8 No.1

In this paper, the scattered electric fields is computed to predict the shielding zone by analysing the effect of the reflected azimuth anlge at the building, and considering the path differences at observation point between the rays from origin and any point in the building. The scattering coefficients, which are applicable to the prediction of shielding zone, are computed and compared with measured one. We found that the scattering power become weak over 10 degree of the azimuth angle at which the scattering coefficient is lower than 40 dB. From this. the shielding zone can be estimated.

구조용강재의 FCAW에 의한 용접부의 미세조직과 기계적 성질

고진현,이완규,황용화 한국기술교육대학교 2001 論文集 Vol.8 No.1

ABSTRACT SM490B structural and SM45C rolled steels were welded in the multilayers with three different heat inputs of 0.6, 0.9 and 1.2kJ/mm and three different shielding gas compositions of 100%CO2, 75%CO2 + 25%Ar and 50%CO2 + 50%Ar. Tensile strength of weldments increased slightly with increasing heat inputs from 0.6 to 0.9kJ/mm whereas that of weldments with heat input of 1.2 kJ/mm decreased. Hardness values of weld metal decreased with increasing heat inputs while Charpy impact values increased with increasing heat inputs. In multilayers of weld metal, the microstructure in the columnar zone of top bead of weld metal consisted of coarser grain boundary ferrite and thicker ferrite side plate, as well as polygonal ferrite with increasing heat inputs. Key words: heat input(입열량), microstructure(미세조직), shielding gas(보호가스), grain boundary ferrite(결정립계 페라이트), carbide(탄화물), hardness value(경도값), impact value(충격값), weld zone(용접부), heat affected zone(열영향부)

단층대와 복합지반을 통과하는 쉴드TBM의 굴진율 및 다운타임 발생 특성 분석

정호영(Hoyoung Jeong),김민철(Mincheol Kim),이민우(Minwoo Lee),전석원(Seokwon Jeon) 한국암반공학회 2019 터널과지하공간 Vol.29 No.6

도심지와 하・해저 터널에서는 연약지반 혹은 특수지반(단층대, 복합지반 등)을 조우할 가능성이 높으며, 이러한 조건에서는 TBM의 굴진율이 저하되고 다운타임이 증가하는 등의 문제점이 발생한다. 이러한 문제점들은 지반조사에서 발견되지 않은 불리한 지반조건에 기인하는 경우가 많으며, 굴진 중 수집된 굴진데이터를 근거로 향후 지층조건에 대한 최적의 운용조건을 결정하는 것이 최선이다. 본 연구는 향후 쉴드 TBM을 이용한 터널공사에서 단층대 및 복합지반에서의 효율적인 시공을 위하여 수행되었다. 외국의 사례를 통해 수집된 TBM의 굴진데이터를 활용하여 굴진율과 다운타임 발생 특성을 지층조건에 따라 분석하였다. 추력, 토크, RPM 등 주요 TBM의 기계데이터와 굴진율, 다운타임은 단층대와 복합지반의 특징에 따라 크게 영향을 받는 것을 확인하였고, 그 특징에 대하여 논하였다. 향후 국내외 유사한 지반에서의 TBM 시공 시 유용하게 활용될 수 있을 것으로 기대된다. Difficult ground conditions (e.g., fault zone and mixed grounds) are highly probable to appear in subsea and urban tunnels because of the shallow working depth and alluvial characteristics. TBM usually experienced decrease of penetration rate and increase of downtime when it meets these difficult ground conditions. The problems are usually caused by the adverse geological conditions, and it is preferable to determine the optimal operational parameters of TBM based on the previous operational data obtained while excavating a preceding tunnel. This study carried out for efficient TBM excavation in fault zone and mixed grounds. TBM excavation data from the tunnel site in Singapore and the characteristics of the TBM excavation data was analyzed. The key operational parameters (i.e., thrust, torque, and RPM), penetration rate, and downtime were highly influenced by the presence of fault zones and mixed grounds, and the features was discussed. It is expected that the results and main discussions will be useful information for future tunneling projects in similar geological conditions.

오버레이용접된 Wrapping Roll의 비드마크제거를 위한 열영향부의 미세조직에 관한 연구

유국종,백응률 대한용접접합학회 2000 대한용접·접합학회지 Vol.18 No.6

In case of overalyered wrapping roll, beadmark shape appear at wrapping roll surface due to irregular wear between weld bead. Irregular wear of this is caused by difference of hardness between weld bead. This study aims at investigating which matrix is good for removing of beadmark at wrapping roll surface. So, we make specimen with martensitic matrix and austenitic matrix. The overlayered alloys were deposited 4 times on a SS41 steel plate using self-shielding flux cored arc welding method. Difference of hardness between weld bead of specimen with matrix of martensite was higher than specimen with matrix of austenite both as-welded and after heat treatment. Therefore, austenitic matrix is between than martensitic matrix for removing of beadmark of wrapping roll surface.