• Title/Summary/Keyword: Transport in soil

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Development of Practical Lumped Contaminant Modeling Approach for Fate and Transport of Complex Organic Mixtures (복잡한 혼합 유기오염물의 거동 예측을 위한 실용적인 오염물 집략화 모델링 기법 개발)

  • Joo, Jin-Chul;Song, Ho-Myeon
    • Journal of Soil and Groundwater Environment
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    • v.14 no.5
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    • pp.18-28
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    • 2009
  • Both feasibility and accuracy of lumped approach to group 12 organic compounds in mixtures into a fewer number of pseudocompounds in sorption processes were evaluated using mixtures containing organic compounds with various physicochemical properties and low-surface-area mineral sorbents. The lumped approach for sorption to simulated mineral sorbents was developed by cluster analysis from statistics. Using the lumped approach, the sorption estimated from both reduced number of pseudocompounds and their sorption parameters (i.e., $K_f$, n) can approximate sorption behavior of complex organic mixtures. Additionally, the pseudocompounds for various mixtures to different types of low-surface-area mineral sorbents can be estimated a priori from the physicochemical properties of organic compound (i.e., ${\gamma_w}^{sat}$). Therefore, the lumped approach may help to simplify the complex fate and transport model of organic contaminant mixtures, reduce experimental efforts, and yet provide results that are statistically identical for practical purposes. Further research is warranted to enhance the accuracy of lumped approach using the multiple regression analysis considering the H-bonding capacity, site concentrations, functional groups for mineral sorbents.

Water Transport Characteristics of Paddy Plow Pan Soils as Estimated by Particle Size Distribution Fractal Dimension (토양입자분포 프랙탈차원을 활용한 논토양 쟁기바닥층 물이동 추정)

  • Han, Kyung-Hwa;Cho, Hyun-Jun;Hur, Seung-Oh;Ha, Sang-Geun;Cho, Hee-Rae;Jeon, Sang-Ho
    • Korean Journal of Soil Science and Fertilizer
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    • v.43 no.1
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    • pp.1-7
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    • 2010
  • This study was carried out to investigate plow pan characteristics and to grasp the relationship between its particle size distribution fractal dimension ($D_m$) and water transport in paddy plow pan. Twenty four soil sampling sites with different management groups, ordinary and sandy-textured, were selected and investigated for physical properties of soils such as Yamanaka hardness in April, non-submerged condition, before rice seedling transplanting. The plow pan appearing depth and thickness was determined by penetration resistance profile. Undisturbed core samples with five replicates were sampled at plow pan layerwith 2 inch cores for measuring soil bulk density and saturated hydraulic conductivity. The particle size distribution fractal dimension ($D_m$) was calculated by the method following the procedure Tylerand Wheacraft (1992), using the USDA-based particle size analysis datawith fractions of 0-0.002, 0.002-0.053, 0.053-0.1, 0.1-0.25, 0.25-0.5, 0.5-1.0, and 1.0-2.0 mm. The plow pan of investigated fields appeared at a range from 5 to 30 cm depth, showing minimum value in sandy-textured management group and maximum value in ordinary management group. The thickness of plow pan were distributed from 5 to 17 cm, showing both minimum and maximum values in sandy-textured management group. Averagely, the plow appearing depth were deeper in ordinary management group than in sandy-textured management group, whereas the reverse in the thickness of plow pan. The particle size distribution fractal dimension ($D_m$) had higher value with finer textures, with higher fractality in coarser texture. Saturated hydraulic conductivities, $K_s$, of plow pan soils distributed from 0.5 to 1420 mm $day^{-1}$, having the highest value in sandy skeletal soils. The $K_s$ decreased with decreasing clay content and $D_m$, showing power function relationships. The coefficient of determination, $R^2$, of the fitted power functions were higher in $D_m$ as x-axis than in clay content. This means that $D_m$ could give us more effective estimation than clay content. Especially, sandy-textured paddy soils had higher $R^2$, compared to ordinary paddy soils. $K_s$ of relatively coarse-textured soils with less than 18%of clay content, therefore, was more dependent on particle size distribution than that of relatively fine-textured soils. From these results, it could be concluded that the fractal scaling gives us a unique quantity describing particle size distribution and then can be applied to estimate saturated hydraulic conductivity, especially more effective in coarse-textured soils.

Permeability and Consolidation Characteristics of Clayey Sand Soils (점토 함유량에 따른 점토질 모래의 투수 및 압밀 특성 평가)

  • Kim, Kwangkyun;Park, Duhee;Yoo, Jin-Kwon;Lee, Janggeun
    • Journal of the Korean Geotechnical Society
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    • v.29 no.3
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    • pp.61-70
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    • 2013
  • Evaluation of permeability and coefficient of consolidation of clayey sand is critical in analyzing ground stability or environmental problems such as prediction of pollutant transport in groundwater. In this study, permeability tests using a flexible wall permeameter are performed to derive the coefficient of consolidation and permeability of reconstituted soil samples with various mixing ratios of kaolin clays and two different types of sands, which are Jumunjin and Ottawa sands. The test results indicate that the coefficient of consolidation and permeability plots linearly against clay contents in semi-log scale graphs for low clay mixing ratios ranging between 10 to 30%. It is also demonstrated that coefficient of consolidation and permeability of sand and clay mixture are dependent on the soil structure. Contrary to previous findings, the permeability is shown to be independent of the void ratio at low mixing ratios, which can be classified as non-floating fabric. The permeability decreases with the void ratio for floating fabric.

Detecting and Extracting Changed Objects in Ground Information (지반정보 변화객체 탐지·추출 시스템 개발)

  • Kim, Kwangsoo;Kim, Bong Wan;Jang, In Sung
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.39 no.6
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    • pp.515-523
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    • 2021
  • An integrated underground spatial map consists of underground facilities, underground structures, and ground information, and is periodically updated. In this paper, we design and implement a system for detecting and extracting only changed ground objects to shorten the map update speed. To find the changed objects, all the objects are compared, which are included in the newly input map and the reference map in the integrated map. Since the entire process of comparing objects and generating results is classified by function, the implemented system is composed of several modules such as object comparer, changed object detector, history data manager, changed object extractor, changed type classifier, and changed object saver. We use two metrics: detection rate and extraction rate, to evaluate the performance of the system. As a result of applying the system to boreholes, ground wells, soil layers, and rock floors in Pyeongtaek, 100% of inserted, deleted, and updated objects in each layer are detected. In addition, it provides the advantage of ensuring the up-to-dateness of the reference map by downloading it whenever maps are compared. In the future, additional research is needed to confirm the stability and effectiveness of the developed system using various data to apply it to the field.

A Study on the Topology Optimization of Nail Arrangement using Stiffened Shape Density (보강 형상밀도를 이용한 네일 배치의 위상최적화 연구)

  • Cho, Chung-Sik;Song, Young-Su;Lee, Su-Gon;Woo, Jae-Gyung;Choi, Woo-Il
    • The Journal of Engineering Geology
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    • v.28 no.4
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    • pp.605-618
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    • 2018
  • Korea follows the slope design criteria during construction. It was enacted by the Ministry of Land, Transport and Maritime Affairs. There are cases where the Soil-nail is designed as a measure to secure slope stability. The arrangement of the soil-nail may be arranged at equal intervals or may be arranged differently depending on the soil failure model. The optimum design of the countermeasure method is determined by securing stability of the slope through optimization of dimensions and shape. However, when uniform nails are placed at low elevations in slopes, the standard safety factor is exceeded, which may hinder economic design. It is preferable to arrange the reinforcement of the nails over the entire slope. When the horizontal spacing of the nails was topology optimized according to the slope height, it was possible to minimize the amount of reinforcement while satisfying the standard safety factor. Since the active load is reduced in the section where the slope height is lowered, the safety factor after reinforcement may be excessively increased. Therefore, the phase optimization method is proposed as an economical optimal design method using the reinforcing shape density. In addition, a relational expression was designed to optimize the horizontal spacing by slope height.

Transports of Ferrihydrite Colloids in Packed Quartz Sand Media (석영모래 속에서의 Ferrihydrite 콜로이드 이동)

  • Kim, Seok-Hwi;Gu, Baohua;Lee, Jae-Hoon;Wang, Wei;Park, Ki-Hoon;Kim, Kang-Joo
    • Journal of the Mineralogical Society of Korea
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    • v.19 no.4 s.50
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    • pp.231-238
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    • 2006
  • Transports of heterogeneously charged particles were investigated based on column experiments. Synthesized mono-dispersed ferrihydrite (${\sim}100nm$) and amorphous $SiO_2\;({\sim}40nm\;and\;{\sim}80nm)$ particles, of which surfaces are oppositely charged under pH < 9.0 (ferrihydrite, positive; amorphous silica, negative), were used. $177{\sim}250{\mu}m$ quartz sand was used as a stationary matrix. The results show that even favorable particles (i.e., ferrihydrite) can show a conservative transport through the oppositely charged media (i.e., quartz) when they coexist with humic acid or with much greater number of oppositely charged particles. These results imply that transports of both negatively and positively charged contaminants may be possible at the same time under a condition of heterogeneous colloidal system.

Analysis of the Driving & Loading Pattern of the Construction Waste Collecting Trucks Using IoT On-Board Truck Scale System (IoT 자중계 시스템을 활용한 건설폐기물 수집·운반 차량의 운행 및 적재패턴 분석)

  • Kim, Jong Woo;Jung, Young Woo
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.19 no.6
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    • pp.74-87
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    • 2020
  • Overloaded trucks are the main source that threatens road safety and directly affects the reduction of pavement life. The On-board truck scale is the only equipment that could prevent overloading by measuring and adjusting the loading weight before driving. Legislation is needed to encourage its installation so that the driver can prevent overloading. In this study, an on-board truck scale system was installed on 30 dump trucks for transporting construction waste, such as soil and aggregates, which are major loads of 36.55% for overloading, and the trucks were monitored remotely. The overload prevention effect was analyzed by comparing driving data for 1 month before distribution of the weight display app that can recognize the weight to the driver and 1 month after distribution. After installation, overloading could be 6.1% reduced, and the transportation efficiency could be increased by checking the weight provided from the On-board truck scale system.

Analysis of Consistency and Accuracy for the Finite Difference Scheme of a Multi-Region Model Equation (다영역 모델 방정식의 유한차분계가 갖는 일관성과 정화성 분석)

  • 이덕주
    • Journal of Korea Soil Environment Society
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    • v.5 no.1
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    • pp.3-12
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    • 2000
  • The multi-region model, to describe preferential flow, is an equation representing solute transport in soils by dividing soil into numerous pore groups and using the hydraulic properties of the soil. As the model partial differential equation (PDE) is solved numerically with finite difference methods. a modified equivalent partial differential equation(MEPDE) of the partial differential equation of the multi-region model is derived to analyze the accuracy and consistency of the solution of the model PDE and the Von Neumann method is used to analyze the stability of the finite difference scheme. The evaluation obtained from the MEPDE indicated that the finite difference scheme was found to be consistent with the model PDE and had the second order accuracy The stability analysis is performed to analyze the model PDE with the amplification ratio and the phase lag using the Von Neumann method. The amplification ratio of the finite difference scheme gave non-dissipative results with various Peclet numbers and yielded the most high values as the Peclet number was one. The phase lag showed that the frequency component of the finite difference scheme lagged the true solution. From the result of the stability analysis for the model PDE, it is analyzed that the model domain should be discretized in the range of Pe < 1.0 and Cr < 2.0 to obtain the more accurate solution.

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An experimental study for the effect of soil plug on the basal heave stability for the vertical shaft excavation in clay (점성토 지반 수직구 굴착 중 히빙 안정성 증가에 대한 관내토 효과에 대한 실험적 연구)

  • Kang, Seok-Jun;Cho, Gye-Chun;Kim, Jung-Tae;Cha, Yohan;Hong, Eun-Soo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.1
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    • pp.183-195
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    • 2018
  • Recently, the need for research on vertical shaft excavation is increasing with the increase of the demands for the underground and utility tunnels. As a part of the R&D project of the Ministry of Land, Infrastructure and Transport, CUT (center for utility tunnel) has developed "Ring cut method". "Ring cut method" is a method to improve the stability of the ground against the basal heave by excavator wall pre-penetration during vertical shaft excavation. In this study, the basal heave was simulated by centrifugal model test. The basal heave, ground subsidence, and ground deformation of surrounding ground were analyzed by soil plug effect from wall pre-penetration. It was found that the soil plug could control the basal heaving and ground subsidence, and verified that the 'Ring cut method' could be a good countermeasure for the ground stability against the basal heave.

Concentration Variations of Persistent Organic Pollutants in Gosan, Jeju during the Polluted Period in November 2001 and the Yellow Sand Period in Spring 2002 (2001년 11월 오염시기와 2002년 봄 황사시기 제주도 고산에서의 잔류성 유기오염물질 농도 변화)

  • 김영성;김진영;김연제;문길주;문광주;한진석;김상우;윤순창;권성안
    • Journal of Korean Society for Atmospheric Environment
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    • v.19 no.5
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    • pp.469-490
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    • 2003
  • Atmospheric concentrations of persistent organic pollutants (POPs) were measured at Gosan, Jeju in November 2001 and spring 2002, each time for two weeks. Primary target pollutants were organochlorine pesticides, coplanar polychlorinated biphenyls (co- PCBs), and dioxin/furans listed in the Stockholm Convention adopted in May 2001. Polycyclic aromatic hydrocarbons (PAHs) were also measured in order to understand the overall characteristics of the POPs distribution as well as PM$_{2.5}$, a potent carrier of POPs. In the latter part of the measurement period of November 2001, almost every pollutant of combustion origin including dioxin/furans went high probably due to influence of emissions in the nearby area. The characteristics of atmospheric environment at Gosan in this period were rather close to urban areas far from those of a background area. A severe dust storm swept for three days at the end of the measurement period of spring 2002. However, changes in pollutant concentrations were relatively small except PM$_{10}$. Nevertheless, increases in particulate PAHs and OCDD (octachlorinated dibenzo-p-dioxins), mostly present in fine particles, were observed. Trends in organochlorine pesticide variations were mixed although possible volatilization of DDT residues from soil was inferred from the measurements of spring 2002.2.2.