• 한국지반공학회논문집
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• 제35권11호
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• pp.37-49
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• 2019

본 연구에서는 매립심도가 손상 하수관으로 인해 형성되는 지하 공동 및 지반함몰에 미치는 영향을 확인하기 위하여 서로 다른 심도로 지반을 조성하여 모형시험을 수행하였다. 모형시험 중에 일정 시간 간격으로 디지털 이미지를 촬영하였으며, PIV 기법을 적용하여 내부 변위 및 변형을 측정하였다. 이와 지표면에서 발생하는 지반 침하, 지하 공동의 크기 등에 대한 분석도 함께 진행하여 거동을 분석하였다. 시험 결과, 매립심도가 낮은 경우의 지반에서 매립심도가 높은 경우에 비해 지하 공동 및 지반함몰 형성에 대한 저항성이 작은 것으로 확인되었다.

• Geomechanics and Engineering
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• 제32권2호
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• pp.145-157
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• 2023

This paper aims at investigating the face stability of large-diameter underwater shield tunnels considering seepage in soft-hard uneven strata. Using the kinematic approach of limit upper-bound analysis, the analytical solution of limit supporting pressure on the tunnel face considering seepage was obtained based on a logarithmic spiral collapsed body in uneven strata. The stability analysis method of the excavation face with different soft- and hard-stratum ratios was explored and validated. Moreover, the effects of water level and burial depth on tunnel face stability were discussed. The results show the effect of seepage on the excavation face stability can be accounted as the seepage force on the excavation face and the seepage force of pore water in instability body. When the thickness ratio of hard soil layer within the excavation face exceeds 1/6D, the interface of the soft and hard soil layer can be placed at tunnel axis during stability analysis. The reliability of the analytical solution of the limit supporting pressure is validated by numerical method and literature methods. The increase of water level causes the instability of upper soft soil layer firstly due to the higher seepage force. With the rise of burial depth, the horizontal displacement of the upper soft soil decreases and the limit supporting pressure changes little because of soil arching effect.

• 한국염색가공학회지
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• 제29권4호
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• pp.181-194
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• 2017

The biodegradability of polylactic acid(PLA) fabrics was evaluated by two methods: enzyme and soil degradation. Three different enzymes were selected to evaluate. Degradation times were measured at optimal enzyme treatment conditions. Biodegradation by enzymatic hydrolysis was compared with soil degradation. As a result, biodegradation created cracks on the fiber surface, which led to fiber thickening and shortening. In addition, new peak was observed at $18.5^{\circ}$ by degradation. Moreover, cracks indicating biofragmentation were confirmed by enzyme and soil degradation. By enzyme and soil degradation, the weight loss of PLA fabrics was occurred, there through, the tensile strength decreased about 25% by enzyme hydrolysis when 21 days after, and 21.67% by soil degradation when 60 days after. Furthermore, the biodegradability of PLA fabrics by enzymatic and soil degradation was investigated and enzymatic degradation was found to be superior to soil degradation of PLA fabrics. Among the three enzymes evaluated for enzymatic degradation, alcalase was the most efficient enzymes. This study established the mechanism of biodegradation of PLA nonwovens, which might prove useful in the textile industry.

• 보존과학회지
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• 제27권4호
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• pp.441-450
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• 2011

이 연구는 토기 재질과 토양 특성에 따라 매장환경이 출토 토기에 미치는 물리화학적 영향을 연구하였다. 이를 위해 대전 학하, 아산 음봉, 화성 소근산 그리고 공주 행정중심복합도시 출토 토기와 토양을 연구 대상으로 하였다. 먼저 토기의 탈염을 통해 용출되는 이온의 화학종과 용출속도를 조사한 결과, 토기의 기공크기와 흡수율에 따라 토기 내 이온유입이 달라졌다. 즉 $1,000^{\circ}C$ 이상의 고온 소성된 토기는 기공이 작고 흡수율이 낮아 매장환경의 염 유입 현상이 거의 일어나지 않았다. 그러나 $800^{\circ}C$ 이하의 저온 소성된 토기는 기공이 크고 흡수율이 높아 다량의 염이 유입되어 증류수 탈염을 통해 염을 제거하였다. 탈염 2일 만에 40~60%의 염이 제거되었고 탈염 1주일 만에 60~80%의 염이 제거되었다. 또한 토양에 포화되어 있는 이온은 대부분 토기에도 동일한 비율로 존재하고 $K_2SO_4$와 같이 토양에 잔존하는 비료의 성분도 검출되었다. 그러나 모래 함량이 상당히 높은 사질 토양시료에서는 함유 이온량이 적어 토기에 유입되는 이온의 영향이 비교적 적었고 미사 및 점토 함량이 높은 토양에 매장되었던 토기는 유입되는 이온함량이 높았다. 그러나 저온소성된 토기에서는 다량 유입된 염에 의한 손상이 우려되므로 세척 이외의 탈염을 통한 염 제거가 필요하며 그 기간은 토기의 상태에 따라 달라질 수 있을 것으로 생각된다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2003년도 추계학술발표대회 요약집
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• pp.443-443
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• 2003

• Geomechanics and Engineering
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• 제30권4호
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• pp.383-392
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• 2022

Although pipelines are composed of segmental tubes commonly connected by rubber gasket or push-in joints, current studies mainly simplified pipelines as continuous structures. Effects of joints on three-dimensional deformation mechanisms of existing pipelines due to tunnel excavation are not fully understood. By conducting three-dimensional numerical analyses, effects of pipeline burial depth, tunnel burial depth, volume loss, pipeline stiffness and joint stiffness on bending strain and joint rotation of existing pipelines are explored. By increasing pipeline burial depth or decreasing tunnel cover depth, tunneling-induced pipeline deformations are substantially increased. As tunnel volume loss varies from 0.5% to 3%, the maximum bending strains and joint rotation angles of discontinuous pipelines increase by 1.08 and 9.20 times, respectively. By increasing flexural stiffness of pipe segment, a dramatic increase in the maximum joint rotation angles is observed in discontinuous pipelines. Thus, the safety of existing discontinuous pipelines due to tunnel excavation is controlled by joint rotation rather than bending strain. By increasing joint stiffness ratio from 0.0 (i.e., completely flexible joints) to 1.0 (i.e., continuous pipelines), tunneling-induced maximum pipeline settlements decrease by 22.8%-34.7%. If a jointed pipeline is simplified as a continuous structure, tunneling-induced settlement is thus underestimated, but bending strain is grossly overestimated. Thus, joints should be directly simulated in the analysis of tunnel-soil-pipeline interaction.

• 한국해양공학회지
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• 제31권3호
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• pp.219-226
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• 2017

In this study, the impact characteristics of subsea pipelines that were installed in various soil types and burial depths were evaluated by a numerical method. An impact scenario replicated a dropped ship anchor that fell vertically and impacted an installed subsea pipeline. In order to calculate the impact force through terminal velocity, FLUENT, a computational fluid dynamic program and MDM (Moving Deforming Mesh) technique were applied. Next, a dynamic finite element program, ANSYS Explicit Dynamics, was used for impact analysis between the anchor and pipeline (or, subsea if they were buried). Three soil types were considered: loose sand, dense sand and soft clay by applying the Mohr-coulomb model to the seabed. The buried depth was assumed to be 0 m, 1 m and 2 m. In conclusion, a subsea pipeline was the most stable when buried in dense sand at a depth of 2 m to prevent impact damage.

• 공업화학
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• 제4권1호
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• pp.178-187
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• 1993

전분-폴리에틸렌 복합필름을 활성오니시험과 토양매립시험에 의해 시험하였으며, 시험동안 전분의 분해에 의해 필름의 형태가 변함을 관찰할 수 있었다. 매트릭스로 사용한 폴리에틸렌은 첨가한 산화촉진제의 작용에 의해 산화되어 가교 및 분해가 모두 일어남을 알 수 있었다. 그러나 토양매립시험 결과로 볼 때 산화촉진제로 옥수수에서 추출한 오일을 사용하였을 경우 수평균분자량 및 중량평균분자량이 모두 감소하고 분자량 분포가 증가하는 분해반응이 우세하게 일어남을 알 수 있었다.

• 한국의류학회지
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• 제28권8호
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• pp.1048-1056
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• 2004

Hydrophilicities of finished cotton fabrics were evaluated in respect of moisture regain and wickability. Changes in internal structure were determined using X-ray diffraction and surface changes in degraded samples were observed through a microscopy. Activated sludge test, soil burial test and enzyme hydrolysis were employed to evaluate the biodegradabilities. In addition, correlation analysis was done between biodegradability and the factors affecting biodegradability in each evalution methods. It was shown that hydrophilicities of silicone finished specimens were lower than that of untreated cotton and decreased in a row of PDMS(polydimethyl siloxane : -CH$_3$)＞AFS(amino functional siloxane ; -C$_3$H$_{6}$ NHC$_2$H$_4$NH$_2$)＞MHPS(methylhydrogen polysiloxane : -H, Cat : (C$_{17}$ H$_{35}$ COO)$_2$Zn) Although, moisture regain of mercerized cotton was higher than those of the others, wickability was shown to be lower. It was represented that crystalinities of cotton fabrics decreased by the silicone treatment. In activated sludge test and soil burial test, biodegradabilities of silicone treated specimens were lower than that of untreated cotton, where specimens of higher biodegradability exhibited higher biodegradability except mercerized ones. The results from enzyme hydrolysis, however, showed somewhat different tendency in that biodegradability was more closely related with the crystallinities of fabrics. It can be thought that enzyme hydrolysis is carried out for short time, physical accessibility becomes important.

• 한국잡초학회지
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• 제4권2호
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• pp.149-153
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• 1984

전작(田作) 및 과수원(果樹園)의 주요(主要) 다년생(多年生) 잡초(雜草)의 하나인 메꽃(Calystegia japonica Choisy)의 생육(生育)에 미치는 pH, 건조시간(乾燥時間), 발생심도(發生深度), 토양수분(土壤水分) 및 광도(光度)의 영향(影響)을 조사(調査)하였다. 메꽃 지하경(地下莖) 생존율(生存率)은 $35^{\circ}C$에서 14시간(時間) 이상(以上) 건조(乾燥)되면 급격(急激)하게 감소(減少)되고, 생존(生存)되더라도 그 생육(生育)은 극히 저조(低調)하였으며, 발생심도(發生深度)가 0cm 혹은 8cm 이하(以下)로 될 때에는 생육(生育)이 크게 떨어졌다. 토양수분(土壤水分) 40~60%가 생육(生育)에 최적수준(最適水準)이었다. 메꽃의 초장(草長)은 광도(光度)의 증가(增加)로 감소(減少)되었지만, 근장(根長)과 건물중(建物重)은 증가(增加)하였다.