• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2000년도 창립총회 및 춘계학술발표회
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• pp.84-89
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• 2000

Parametric studies based on laboratory pilot tests were performed to investigate the relationships between electrical resistivity and contaminated soil properties. Three kinds of sandy soils sampled and leachates from a industrial waste landfill were mixed to model the contaminated soils. Electrical resistivity of soils were measured by using a simulated resistivity cone penetrometer probe. In the experiments, the electrical resistivity were observed with changing the water content, void ratio, unit weight, degree of saturation, and concentration of the leachate. The test results show that the electrical resistivity of soils depends largely on the water content and the electrical property of pore water rather than unit weight and types of soils.

• Geomechanics and Engineering
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• 제14권3호
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• pp.283-291
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• 2018

Cracks in soil provide significant preferential pathways for contaminant transport and rainfall infiltration. Water exchange between the soil matrix and crack is crucial to characterize the preferential flow, which is often quantitatively described by a water exchange ratio. The water exchange ratio is defined as the amount of water flowing from the crack into the clay matrix per unit time. Most of the previous studies on the water exchange ratio mainly focused on cracked sandy soils. The water exchange between cracks and clay matrix were rarely studied mainly due to two reasons: (1) Cracks open upon drying and close upon wetting. The deformable cracks lead to a dynamic change in the water exchange ratio. (2) The aperture of desiccation crack in clay is narrow (generally 0.5 mm to 5 mm) which is difficult to model in experiments. This study will investigate the water exchange between a deformable crack and the clay matrix using a newly developed experimental apparatus. An artificial crack with small aperture was first fabricated in clay without disturbing the clay matrix. Water content sensors and suction sensors were instrumented at different places of the cracked clay to monitor the water content and suction changes. Results showed that the water exchange ratio was relatively large at the initial stage and decreased with the increasing water content in clay matrix. The water exchange ratio increased with increasing crack apertures and approached the largest value when the clay was compacted at the water content to the optimal water content. The effective hydraulic conductivity of the crack-clay matrix interface was about one order of magnitude larger than that of saturated soil matrix.

• 한국지반환경공학회 논문집
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• 제14권12호
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• pp.5-12
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• 2013

본 연구에서는 인공강우의 침투 배수에 의한 모형사면의 침투거동을 정확히 파악하고자 대구 경북권의 화강풍화토를 이용한 실내모형실험을 수행하였다. 강우의 침투과정과 배수과정에 대한 함수비와 모관흡수력 변화를 측정하고 부정류상태의 수치해석을 수행하여 두 결과를 비교하였다. 실험결과, 함수비와 모관흡수력의 거동은 사면의 상부, 중간부, 하부 영역에 따라 침투 거리와 하부 배수층의 영향으로 다르게 나타났다. 공극 속 지하수량 변화에 따른 투수계수 변화는 침투과정에서 함수비 증가 및 모관흡수력 감소를 즉각적이고 큰 값으로 유발하였다. 그러나 배수과정에서는 함수비 감소 및 모관흡수력 증가가 완만하고 작은 값으로 발생하였다. 강우로 인한 체적함수비와 모관흡수력이 위치에 따라 값의 차이는 있지만, 침투 및 배수시간에 따른 전형적인 함수특성곡선을 나타내었다.

• 한국농공학회논문집
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• 제63권6호
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• pp.131-140
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• 2021

It is becoming more important to utilize reclaimed lands in South Korea, due to the increasing competition for its usage among different sectors. However, the high groundwater level and poor permeability are exposing them to deterioration by salinization. Salinization is difficult to predict because the pattern changes according to various characteristics of soil and groundwater. In this study, the capillary rising time was studied by the water content profile in the soil. The prediction equation of soil salinity was developed based on simulation result of the CHEMFLO model. to enable prediction considering various soil water content and groundwater level. The two terms constituting the equation showed the coefficients of determination of 0.9816 and 0.9824, respectively. Using the prediction equation of the study, the surface salinity can be easily predicted from the initial surface salinity and the salinity of the groundwater. In the future, more precise predictions will be possible with the results of studies on the hydraulic characteristics of various reclaimed soils, changes in water content profile by seasonal and climate events.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2012년도 학술발표회
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• pp.34-34
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• 2012

Heavy storms rainfall has caused many landslides and slope failures especially in the mountainous area of the world. Landslides and slope failures are common geologic hazards and posed serious threats and globally cause billions in monetary losses and thousands of casualies each year so that studies on slope stability and its failure mechanism under rainfall are being increasing attention of these days. Rainfall-induced slope failures are generally caused by the rise in ground water level, and increase in pore water pressures and seepage forces during periods of intense rainfall. The effective stress in the soil will be decreased due to the increased pore pressure, which thus reduces the soil shear strength, eventually resulting in slope failure. During the rainfall, a wetting front goes downward into the slope, resulting in a gradual increase of the water content and a decrease of the negative pore-water pressure. This negative pore-water pressure is referred to as matric suction when referenced to the pore air pressure that contributes to the stability of unsaturated soil slopes. Therefore, the importance is the study of saturated unsaturated soil behaviors in evaluation of slope stability under heavy rainfall condition. In an actual field, a series of failures may occur in a slope due to a rainfall event. So, this study attempts to develop a numerical model to investigate this failure mechanism. A two-dimensional seepage flow model coupled with a one-dimensional surface flow and erosion/deposition model is used for seepage analysis. It is necessary to identify either there is surface runoff produced or not in a soil slope during a rainfall event, while analyzing the seepage and stability of such slopes. Runoff produced by rainfall may result erosion/deposition process on the surface of the slope. The depth of runoff has vital role in the seepage process within the soil domain so that surface flow and erosion/deposition model computes the surface water head of the runoff produced by the rainfall, and erosion/deposition on the surface of the model slope. Pore water pressure and moisture content data obtained by the seepage flow model are then used to analyze the stability of the slope. Spencer method of slope stability analysis is incorporated into dynamic programming to locate the critical slip surface of a general slope.

• Geomechanics and Engineering
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• 제28권6호
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• pp.599-611
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• 2022

Tendon reinforced cemented soil is applied extensively in foundation stabilisation and improvement, especially in areas with soft clay. To solve the deterioration problem led by steel corrosion, the glass fiber-reinforced polymer (GFRP) tendon is introduced to substitute the traditional steel tendon. The interface bond strength between the cemented soil matrix and GFRP tendon demonstrates the outstanding mechanical property of this composite. However, the lack of research between the influence factors and bond strength hinders the application. To evaluate these factors, back propagation neural network (BPNN) is applied to predict the relationship between them and bond strength. Since adjusting BPNN parameters is time-consuming and laborious, the particle swarm optimisation (PSO) algorithm is proposed. This study evaluated the influence of water content, cement content, curing time, and slip distance on the bond performance of GFRP tendon-reinforced cemented soils (GTRCS). The results showed that the ultimate and residual bond strengths were both in positive proportion to cement content and negative to water content. The sample cured for 28 days with 30% water content and 50% cement content had the largest ultimate strength (3879.40 kPa). The PSO-BPNN model was tuned with 3 neurons in the input layer, 10 in the hidden layer, and 1 in the output layer. It showed outstanding performance on a large database comprising 405 testing results. Its higher correlation coefficient (0.908) and lower root-mean-square error (239.11 kPa) were obtained compared to multiple linear regression (MLR) and logistic regression (LR). In addition, a sensitivity analysis was applied to acquire the ranking of the input variables. The results illustrated that the cement content performed the strongest influence on bond strength, followed by the water content and slip displacement.

• 한국산학기술학회논문지
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• 제10권11호
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• pp.3287-3295
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• 2009

본 연구는 강우재현장치를 제작하고, 화강암질 풍화토로 조성된 모형사면에 강우 및 사면조건에 따라 모형실험과 수치해석을 실시하였다. 모형실험에서 계측된 체적함수비와 간극수압의 변화특성을 분석하였으며 또한 수치해석 결과와 비교하였다. 체적함수비는 강우강도가 크고 사면경사가 급할수록 한계값에 도달하는데 짧은 시간이 소요되는 반면 강우강도가 작고 사면경사가 완만할수록 많은 시간이 소요되는 것으로 나타났다. 강우강도가 작고 강우지속시간이 짧을수록 더 큰 부의 간극수압을 나타내고 회복하는 시간도 짧은 것으로 나타났다. 이와 반면 강우강도가 크고 강우지속시간이 길수록 부의 간극수압을 회복하는데 오랜 시간이 소요되는 것으로 나타났다. 강우재현 모형실험과 수치해석을 수행한 결과 체적함수비와 간극수압의 분포경향이 유사하게 나타났다. 그러나 체적함수비는 최대 5% 정도, 간극수압은 최대 3kPa 정도의 차이를 보였다.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2019년도 추계학술대회
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• pp.19-19
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• 2019

It is necessary to maintain stable crop productions under the unsuitable environments, because the drought and flood may be frequently caused by the global warming. Therefore, it is agent to improve the crop growth model corresponded to soil moisture status. Chili pepper (Capsicum annuum) is one of the useful crop in Asia, and then it is affected by change of precipitation in consequence drought and flood occur however crop model to evaluate water stresses on chili pepper is not enough yet. In this study, development of crop model under different soil moisture status was attempted. The experiment was conducted on the slope fields in the greenhouse. The water level was kept at 20cm above the bottom of the container. Habanero (C. chinense) was used as material for crop model. Sap bleeding rate, SPAD value, chlorophyll content, stomatal conductance, leaf water potential, plant height, leaf area and shoot dry weight were measured at 10 days after treatment (DAT) and 13 DAT. Moreover, temperature and RH in the greenhouse, soil volume water contents (VWC) and soil water potential were measured. As a result, VWC showed 4.0% at the driest plot and 31.4% at the wettest plot at 13 DAT. The growth model was calculated using WVC and the growth analysis parameters. It was considered available, because its coefficient of determination showed 0.84 and there are significant relationship based on plants physiology among the parameters and the changes over time. Furthermore, we analyzed the important factors for higher accuracy prediction using multiple regression analysis.

• 한국토양비료학회지
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• 제28권3호
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• pp.227-232
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• 1995

토양수분장력을 실측하지 않고도 토양수분장력을 추정하기 위하여, 입경분포가 서로 다른 10가지 토성의 134점 토양시료를 채취하여 토양수분함량과 토양 수분장력을 측정한 후 scaling technique을 이용하여 토양수분특성곡선을 추정할 수 있는 모형을 개발하고, 별도의 205개 토양에 대하여 이 모형에 대한 실효성 검정을 한 결과는 다음과 같다. 1. 토양수분함량 측정치(${\theta}i$)에 대하여 토양수분장력이 10KPa 때와 1.5MPa 때의 수분함량을 이용하여 ${\theta}^*=[{\theta}i-{\theta}(1.5MPa)]$/$[{\theta}(10KPa)-{\theta}(1.5MPa)]$와 같이 scale변화된 수분함량(${\theta}^*$)을 구하도록 하였다. 2. Scale변환된 수분함량(${\theta}^*$)을 이용하여 토양수분 특성곡선을 구한 결과 토성별 계수의 차이가 거의 없이 H[unit : 0.1MPa]=$0.13{\cdot}({\theta}^*)^{-2.04}$로 나타낼 수 있었다. 3. 포장용수량과 위조점에서의 수분함량은 scale변환된 모래([S]) 및 미사함량([Si])과 유기물함량([OM])을 다음 식에 의해 그 추정이 가능하였다. ${\theta}(10KPa)=26.80-3.99ln[S]+2.36{\sqrt{[Si]}}+2.88[OM]$ ($R=0.81^{**}$) ${\theta}(1.5KPa)=15.75-2.86ln[S]+0.55{\sqrt{[Si]}}+0.70[OM]$ ($R=0.76^{**}$) 위 식에 의해 205개 토양별로 $\theta$(10KPa) 및 $\theta$(1.5MPa)를 측정한 후 이 값에 의거하여 산출된 ${\theta}^*$를 추정식에 적용하여 ${\theta}(1/30MPa)$를 추정하고 이 추정치와 실측치를 1 : 1 line상에서 비교해 본 결과, 실측치와 추정치는 아주 근사한 값($R=0.85^{**}$)을 나타내었다.

• 한국지반공학회논문집
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• 제18권5호
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• pp.67-72
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• 2002

포장내의 흙들의 함수비는 강우, 온도 등의 기후적 요인에 따라 계절적으로 변화한다. 그것은 강우로인한 동수경사가 습기의 흐름을 유발하고, 온도변화로 인한 온도경사가 직.간접적으로 열흐름뿐만아니라 습기의 흐름을 유발하기 때문이다. 포장내의 흙들은 보통 불포화상태로 존재한다. 그리고 열의 흐름과 습기의 흐름은 상호간에 복잡한 작용을 하는 복합적인 과정들로 인식되어 왔다. 이 논문은 불포화토내의 복합적인 열의 흐름과 습기의 흐름에 대해 유한요소법을 이용한 하나의 일차원적 분석모델을 제시한다. 이 모델은 온도와 함수비 변화뿐만아니라 시간에 따른 동상을 예측하기 위하여 사용될 수 있다. 온도 및 함수비의 변화 그리고 동상의 예측은 포장의 설계 및 유지관리를 위해 의미 있는 일이 될 것이다. 이 모델은 다른 모델의 결과들과 비교를 통해서 검증된다.