Effect of Applied Voltage on the Reliability of Coating Flaw Detection of Pipe with Different Buried Depths

김영식,임부택,김민기,김기태,장현영 한국부식방식학회 2019 Corrosion Science and Technology Vol.18 No.6

External corrosion control of buried pipe can be achieved by the combination of barrier coating and cathodic protection. Coating damage and deterioration can be induced by many reasons; damage during handling and laying, enhanced failure at low temperatures, failure during commissioning and operation, disbanding due to inadequate surface cleaning, rock penetration during installation and service etc. This work focused on the effect of survey conditions on the reliability of coating flaw detection of buried pipes. The effects of applied voltage and anode location on the detection reliability of coating flaw of buried pipe in soil with the resistivity of ca. 25.8 kΩ·cm were discussed. Higher applied voltage increased the detection reliability, regardless of buried depth, but deeper burial depth reduced the reliability. The location of the anode has influenced on the detection reliability. This behaviour may be induced by the variation of current distribution by the applied voltage and buried depth. From the relationship between the applied voltage and reliability, the needed detection potential to get a desire detection reliability can be calculated to get 100% detection reliability using the derived equation.

수심과 퇴적 깊이 변화에 따른 해저배관의 하중지지능력 평가

백종현(Jong-hyun Baek),김영표(Young-pyo Kim),김우식(Woo-sik Kim) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.10

해저배관은 부력과 외부 충격을 방지하기 위하여 1.2∼4m의 매설 깊이로 설치되어 운영된다. 해저배관은 수압과 토하중에 의한 외압으로부터 소성붕괴에 대한 저항성을 가져야한다. 해저배관에 수압과 토하중으로 발생하는 원주응력을 유한요소해석으로 파악하여 배관의 건전성에 미치는 영향을 평가하였다. 내압은 외압에 의한 소성붕괴 저항성을 향상시켜 소성붕괴 발생 깊이를 증가시켰다 동일 수심에서는 매설 깊이 증가에 따라 원주응력은 증가하나, 동일 매설 깊이에서는 수심이 증가함에 따라 배관에서 발생하는 원주응력은 감소한다. Subsea pipelines have been operated with buried depths of 1.2-4m underneath the seabed to prevent buoyancy and external impacts. Therefore, they have to show resistance to both the soil load and the hydrostatic pressure. In this study, the structural integrity of a subsea pipeline subjected to soil load and hydrostatic pressure was evaluated by using FE analyses. A parametric study showed that the internal pressure increased the plastic collapse depth by increasing the resistance to plastic collapse. The hoop stress increased with an increase in the buried depth for the same water depth; however, the hoop stress decreased with an increase in the water depth for the same buried depth.

Optimal Design of Central Drainage Ditch Buried Depth for Highway Tunnel in Seasonally Frozen Region

Yuanfu Zhou,Mingyong Li,Danfeng Zhang,Xiaoqing Suo,Xuefu Zhang,Ke Dong 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.4

In seasonally frozen regions, the drainage ditch of highway tunnels is usually set below the maximum frost depth. Hence, the deeply buried drainage ditch is often used, which increases the cost, difficulty, and time of tunnel construction. And it affects the stability of the surrounding rock and the tunnel structure safety. To solve these difficulties, this study investigated the optimal design of buried depth of central drainage ditch by numerical simulation. Based on a tunnel in Northwest China, a transient heat transfer model, which involves heat conduction and phase transition, was established. Then, the influences of different water amounts and thermal insulation technologies on the minimum buried depth of central drainage ditch were investigated. The results indicate that the thermal insulation layer, regardless of whether it is an internal thermal insulation layer, external thermal insulation layer, or foam concrete backfilled in invert arch, can prevent the drainage ditch from freezing and increase its elevation. The findings of this study can be helpful in optimizing the buried depth, selecting reasonable thermal insulation technology for central drainage ditch in seasonally frozen regions.

Weed Emergence as Affected by Burying Depth and Water Management

Byeong-Cheul Moon,Sung-Tae Park,Soon-Chul Kim,Suk-Ju Kwon,Andrew Martin Mortimer,Collin Piggin 韓國作物學會 1999 Korean journal of crop science Vol.44 No.1

The experiment was conducted to investigate emergence response of lowland weeds at different soil moisture contents, burying depths and upon changes in soil moisture. Rice germination was over 50% at all burying depths under aerobic condition, but the emergence rate of the soil surface placed seeds in saturated and flooded conditions decreased by 19% and 29%, respectively, as compared with that of aerobic condition. Rice seeds at burying depth of over 3 cm did not emerge at all. The emergence rate of Echinochloa crus-galli (L.) Beauv. in aerobic condition was lower than 30%, but the emergence pattern of E. crus galli (L.) Beauv. at different soil moisture contents and seeding depths was similar to that of rice. Emergence behavior of lschaemum rugosum Salisb., Ludwigia octovalvis (Jacq.) Raven and Sphenoclea zeylanica Gaertn. which are dominant lowland weed species in the Philippines also differed depending on soil moisture conditions and burying depths. lschaemum rugosum Salisb. emerged at all burying depths under aerobic condition, whereasLudwigia octovalvis (Jacq.) Raven emerged only at 0 cm deep under saturated and aerobic condition and Sphenoclea zeylanica Gaertn. at 0 cm deep under flooding condition. Weed seeds planted at 1, 3, and 5 cm deep in continuous flooded and saturated condition did not emerge at all, but upon a change of soil moisture condition from saturated to drainage (S~rightarrow D) and flooded to drainage (F~rightarrow D), grass weeds began to germinate again and the average emergence rate in S~rightarrow D and F~rightarrow D were 26% and 5% forE. crus-galIi (L.) Beauv., 9% and 8% forI. rugosum SaIisb., respectively. Weed seeds buried in soil in the pot showed great emergence at S~rightarrow D but did not emerge under continuous flooded condition. The diversity index accounting for dominance degree and occurrence aspect of weed, was the lowest at F~rightarrow D.

건설 현장 항타 하중에 의한 지중 삼중관 진동 거동

유한규(Han Kyu Yoo),원종화(Jong Hwa Won),최정현(Joung Hyun Choi),김문겸(Moon Kyum Kim) 한국가스학회 2011 한국가스학회지 Vol.15 No.4

본 연구는 매설 조건이 불건전한 건설 현장에 매설된 삼중관이 항타 진동에 노출되었을 경우에 발생하는 배관의 거동을 매설 심도에 따라 분석하였다. 매설 배관으로부터 20m의 이격 거리를 갖는 항타 에너지는 7tonf의 램이 1.2m에서 낙하하였을 경우로 선정하였고, 매설 심도는 0.6, 1.4, 2.2, 3.0, 3.8m로 변화하여 연구를 진행하였다. 관의 길이방향 중심에서의 진동 속도와 응력을 확인 하였고, 감쇠비를 고려하여 삼중관의 거동을 분석하였다. 이격거리가 동일한 경우의 진동 속도에 대한 감쇠율은 매설 심도가 증가함에 따라 증가하는 추세를 보이고 있다. 또한, 내관에서 응력 감쇠율도 매설 심도가 증가함에 따라 증가하는 추세를 보이고 있다. This study presents the behavior characteristics of buried three-layered pipeline subjected to pile driving loads corresponding to its cover depth. The analysis considered the driving energy caused by 7 tonf of ram weight and 1.2m of stroke with 20m distance from buried pipeline for all the analysis cases. A cover depth of pipe is varied 0.6m to 3.8m for this research. Vibration Velocity and stress are investigated at the center section in longitudinal direction. With same distance from pile, attenuation ratio of vibration velocity for increment of cover depth has shown an increasing trend. Also, Stress attenuation ratio of inner pipe is increased with cover depth.

Analysis of Asymmetric Stress Ratio in Shallow Buried Tunnels

Qingyang Yu,Zeyu Song,Chao Du,Zhenxue Dai,Shangxian Yin,Mohamad Reza Soltanian,Mojtaba Soltanian,Wei Liu 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.6

Asymmetric stress occurs in shallow buried highways and railway tunnels. Due to asymmetricalloading, the design process of the tunnel is different from a regular tunnel. Chinese code for designing railway tunnel contains empirical values for different grounding rock to facilitate engineering judgement of asymmetrical loading tunnels based on the slope angle of surface and the burial depth of the tunnel. However, when calculating the asymmetric stress, there seem to be no quantitative criteria for estimating the asymmetric stress. Thus, in this work we create a numerical model to better evaluate the asymmetric stress ratios in different rock types. Our results demonstrate for surrounding rocks of grade V with poor stability, an asymmetrical loading conditions should be considered specifically when the stress ratio at the spandrel is higher than unity. For surrounding rock with grade IV in which stability slightly increases we found that the tunnel is asymmetrical once the stress ratio at the spandrel reaches to above 2 − 3. For the grade IV with a higher stability, an asymmetrical loading should be considered in the design when the stress ratio reaches to 3 − 4. For rock with grade III with the maximum stability only when the stress ratio is higher than 7 − 8, the asymmetrical loading conditions should be considered. We found that for grades III, IV, and V, the stress ratio of sidewall is about unity under various slope angles and burial depth. Importantly, we show that the stress ratio at the sidewall cannot be used to make judgements on whether the shallow buried tunnels are asymmetrical loading conditions. Our results have practical implications in design, safety, and risk analyses of tunnels.

매설심도에 따른 가스 배관의 응력 변형 특성

조진우(Jinwoo Cho),최봉혁(Bonghyuck Choi),조원범(Wonbeom Cho),김진만(Jinman Kim),홍성경(Seongkyeong Hong),정석영(Sekyoung Jeong),김준호(Joonho Kim) 한국가스학회 2013 한국가스학회지 Vol.17 No.5

최근 들어 다양한 재료 및 제조기술의 개발로 가스관 품질이 향상되어 매설심도를 저심도화 할 수 있는 환경이 조성되고 있다. 또한 선진 외국과 비교하여 국내 매설깊이 기준이 약 50cm 정도 깊은 것으로 조사되어 시공비용, 차량지체비용 등을 고려하였을 때 비효율적인 매설깊이 규정인 것으로 판단된다. 따라서 본 연구에서는 매설깊이 변화(0.8m, 1.0m, 1.2m)에 따른 가스관의 응력 및 변형 거동을 분석하였다. 본 연구에서는 수치해석 및 현장시험을 통하여 매설심도 변화에 따른 가스관(API 5L)의 거동특성을 분석하였다. 분석결과, 매설심도의 감소가 가스관의 응력, 변형 특성에 큰 영향을 미치지 않을 것으로 판단되었다. Recently, improvement of materials and technologies for the manufacturing of gas pipe has it possible to reduce the buried depth. Compared to the criteria from advanced countries, Korea has conservative criteria for the buried depth of pipeline(about 50cm deeper). Therefore, this study investigated the effect of various buried depth(0.8m, 1.0m, 1.2m) on the stress and strain distribution of gas pipe. Numerical analysis and field tests were carried out with API 5L steel gas pipes. From the results, it can be suggested that the change of buried depth would not significantly affect the stress and strain distribution of gas pipe.

하수관거 직경과 심도를 고려한 하수관거 플라스틱 받침기초의 안전성 평가를 위한 해석연구

박래진(Park, Rae-Jin),박종섭(Park Jong-Sup) 한국산학기술학회 2015 한국산학기술학회논문지 Vol.16 No.6

하수관거 시설은 현장 시공시 다짐 불량 및 뒤채움재의 품질관리 미흡으로 인해 하수관거의 이격 및 부등침하가 발생되고, 이음부나 관의 손상이 심화되는 경우 누수가 발생된다. 노후화로 인해 유지 및 보수, 신설 비용은 매년 증가하고, 누수로 인한 인접 매립시설물 및 지하수로의 유입으로 인해 오염사례가 보고된 바 있으며, 최근에는 싱크홀의 문제를 야기하 여 사회적 관심이 증대되었다. 따라서 많은 연구자들에 의해 하수관거의 기초에 대한 채움재관련 연구가 오랫동안 연구되어 왔으며, 신재생재료에 대한 관심 수요가 증가하여 재생재료를 활용한 연구들도 활발히 진행되고 있다. 본 연구에서는 하수관 거를 지지하는 기초의 안전성과 경제성을 동시에 지닌 재활용재료를 활용한 조립식 하수관거 기초에 대해 연구를 진행하였 으며, 사후처방방식이 아닌, 시공단계에서 사전예방하기 위해 관경 600mm, 700mm, 800mm의 대형 하수관거를 선정하여 적 절한 설계 하중을 산출하고 매립 심도별 안전성에 관한 연구를 수행하였다. 본 연구결과는 신형식 하수관거 기초의 유사연구 에 널리 활용 될 수 있을 것이다. Improper backfill materials and compaction controls under pipelines have become one of the major causes of failure in many sewage pipeline systems. A study on backfill materials and compaction controls has been considered for a long time. However, structural supporters under the pipe were recently concerned because of pipeline repair and maintenance. This paper presents a prefabricated plastic foundation for supporting a sewage pipe system and increasing the performance function of the pipes. Several analytical models for the plastic foundations were investigated using finite-element program, ABAQUS, for checking safety. Comparing with the results of analyses, some of economic design sections based on the sizes of pipe diameters, 600mm, 700 and 600mm, were evaluated. These results could be applied to a pipeline system with a prefabricated plastic foundation with respect to pipe diameters and buried depths.

멸종위기 야생생물I급 흰수마자의 모래 선택과 잠입 행동에 관한 연구

김근식,허문성,김진,박창득,윤주덕 한국하천호수학회 2023 생태와 환경 Vol.56 No.4

To determine the cause of the population decline in Gobiobotia naktongensis, substrate preference and burying behaviour were investigated in this study. In general, the species was shown to prefer a substrate size of 1 mm or less, depending on the flow. In addition, the burying depth varied according to the size of the fish and increased with a decrease in water temperature. Our findings showed that the main cause of the population reduction was the physical changes in the substrate structure due to the dams or barrages construction. Notably, the accumulation of silt and mud in the substrate upon the formation of an upstream lentic water region for structural construction and bed armouring caused by scouring and reduced downstream inflow of fine sediment were deterministic in the fish habitat changes, causing problems in burying. As sand substrate structure is critical for the survival and inhabitation of psammophilous species, efficient strategies should be developed with proper habitat management to reduce the anthropogenic damage

Study on deformation law of surrounding rock of super long and deep buried sandstone tunnel

Ding, Lujun,Liu, Yuhong Techno-Press 2018 Geomechanics & engineering Vol.16 No.1

The finite difference software Flac3D is used to study the influence of tunnel burial depth, tunnel diameter and lateral pressure coefficient of original rock stress on the stress and deformation of tunnel surrounding rock under sandstone condition. The results show that the maximum shear stress, the radius of the plastic zone and the maximum displacement in the surrounding rock increase with the increase of the diameter of the tunnel. When the lateral pressure coefficient is 1, it is most favorable for surrounding rock and lining structure, with the increase or decrease of lateral pressure coefficient, the maximum principal stress, surrounding displacement and plastic zone range of surrounding rock and lining show a sharp increase trend, the plastic zone on the lining increases with the increase of buried depth.