함수특성에 근거한 국내 풍화토의 불포화 투수곡선 추정

김윤기,최경림,이성진,이승래,권형석 한국지반공학회 2010 한국지반공학회논문집 Vol.26 No.10

Unsaturated permeability function is an important factor in the design and analysis of various unsaturated soil structures. Generally the permeability characteristics decrease as the matric suction increases and the trend is similar to water retention characteristics of a soil. The permeability of unsaturated soils can be obtained directly by laboratory tests or indirectly by estimation methods from other soil properties. For unsaturated soils sampled from 7 areas in KOREA, SWCCs and unsaturated permeability functions were obtained by experimental tests. The unsaturated permeability results were also compared with the unsaturated permeability functions derived from the SWCCs theoretically. However, the current estimation models of unsaturated permeability function did not express the unsaturated permeability characteristics. Therefore, the FXK-M permeability function was modified to predict more accurate permeability functions for Korean weathered soils using a correction factor that can be calculated from the air-entry value of SWCC. The new estimation model resulted in good agreements for all tested soils.

중금속 오염 농경지의 식물유효태 예측 모델식 개발: 우리나라 폐광산 인근 농경지 토양 사례 연구

임가희 ( Ga Hee Lim ),김계훈 ( Kye Hoon Kim ),서병환 ( Byoung Hwan Seo ),김권래 ( Kwon Rae Kim ) 한국환경농학회 2014 한국환경농학회지 Vol.33 No.4

BACKGROUND: Application of the transfer functions derived from local soil data is necessary in order to develop proper management protocols for agricultural soils contaminated with heavy metals through phytoavailability control of the heavy metals. The aim of this study was to derive the transfer functions of Korean agricultural soils affected by the abandoned mining sites and evaluate suitability of the derived transfer functions. METHODS AND RESULTS: 142 agricultural soils affected by the abandoned mining sites were collected and analyzed. Two extraction methods, including 1 M NH4NO3 extraction and 0.01 M Ca(NO3)2 extraction were applied to determine phytoavailable metal pools in soils. Multiple stepwise regression of phytoavailable metal pools against the corresponding total metal concentration and soil properties was conducted to derive suitable transfer functions for estimating phytoavailable heavy metal pools. Applicability of the derived transfer functions was examinedby calculating NME and NRMSE. CONCLUSION: Soil pH and organic matter were valid variables for derivation of the transfer functions which were applicable for estimating phytoavailable metal concentrations in the soils being contaminated by heavy metals. In addition, it was confirmed that transfer functions need to be developed based on local soil conditions to accurately estimate heavy metal-phytoavailability.

The Research Review of Soil Ecosystem Services

Byungkeun Hyun,Changhun Lee,Sangho Jeon,Sukyoung Hong,Youngsun Zhang 한국토양비료학회 2018 한국토양비료학회지 Vol.51 No.4

Recently, there is growing interest in agricultural public service function. Studies on soil ecosystem services in addition to its agricultural multi-functionality are underway. Ecosystem services and agricultural multi-functionality have a common denominator of soil. To extend the concept, scope, and context of agricultural public services, it can be extended on the basis of soil functions. Therefore, the results of ecosystem services research related to soil are summarized. Recently, ecosystem services are classified into four categories. Ecosystem services of FAO are divided into provisioning services, regulating services, supporting services, and cultural services. The provisioning services included crop production and water resource. Regulating services are soil related functions such as carbon sequestration, waste treatment, water purification, flood control, erosion prevention, and nutrient supply. Supporting services are biodiversity functions. Ecosystem services can be divided into annual value and total asset value. The nutrient content function and carbon sequestration function can be evaluated at annual value, and also nutrient and carbon contents assessment can be evaluated by stock. They suggest additional soil functions as follows; the energy supply function through biomass, the rare earth supply, the production of medicines, the removing pollutant such as fine dust, drought resistance and soil nitrogen fixation.

Estimating soil water retention function from its particle-size distribution

이태규,노희명 한국지질과학협의회 2014 Geosciences Journal Vol.18 No.2

Knowledge of the soil water retention curve (SWRC)is indispensable for characterizing and modeling water flow andsolute transport in soils. However, since direct measurement of theSWRC in a laboratory is expensive, time-consuming, and laborious,the SWRC has been frequently estimated from more easilymeasurable soil properties. Previously, we formulated an asymmetry-based pore-solid fractal (PSF) model that addresses asymmetriesin fractal dimensions between the distributions of particlesize(PSD) and pore-size (POD) to better estimate the SWRC fromthe PSD data of a soil. Despite this effort, however, the asymptoticproblems of a single power-law function when soil water contentsare close to saturation still remains unresolved. To overcome suchdrawbacks, we addressed functional similarities between the cumulativePSD (cPSD) and the SWRC to avoid the asymptotic problemsand the concept of the slope of the SWRC at its inflection point totreat a bimodal POD, and evaluated the performance of both modelsusing experimental PSD and SWRC data from the UNSODAdatabase (103 soils for model calibration and 46 soils for model validation). Some limitations of the performance of the models werediscussed by applying the models to various soils. The fit of the cPSDand the SWRC to the calibration dataset showed that both modelsperformed well irrespective of soil textures and the square of thePearson product-moment correlation coefficient was 0.987 and 0.965,respectively. The values of the inflection points of the cPSD (pc)increased with increasing sand fraction, while those of the SWRC(hc) decreased, indicating that coarse-textured soils had smallerparticle-size and larger suction head at the inflection points thanfiner-textured soils. Quadratic regression relationship between theshape-related parameters (mp for the cPSD and mh for the SWRC)showed that the magnitude of mh changed little in the lower rangeof mp but increased abruptly in the higher range of mp, indicatingthat the slope of the SWRC becomes steeper as the soil texturebecomes coarser. Overall, the cPSD model fitted the measureddata reasonably well, indicating that the residual fraction (Fr) thataccounts for the contribution of fine-size colloidal fraction to soilwater retention was adequate. Validation results with various soilsshowed that the performance of the SWRC model was dependenton the accuracy of the estimated inflection point. Although thecPSD model performed better than the SWRC model, the fittingresults indicated that the adoption of functional similarities betweenthe cPSD and the SWRC and the concept of point of inflection wasadequate.

정화토양의 토양질 평가

이용민(Yong Min Yi),성기준(Kijune Sung) 한국생태공학회 2022 한국생태공학회지 Vol.9 No.1

Since the use of the remediated soil is undetermined, the quality of the soil should be appropriately evaluated according to its future use. In this study, we developed a soil quality assessment method that can be applied to soils after the remediation process. Soil quality was assessed based on soils that require productivity for use in agricultural fields and landscaping in uncontaminated, contaminated, and remediated cases using soil washing, landfarming, and thermal desorption. The results showed that the quality of soil washing treated deteriorated the most compared to landfarming and thermal desorption-treated soil, assessed based on the case of use as field soil. In the case of thermal desorption, the range of reduction was smaller than that of soil washing, but soil quality decreased slightly after remediation. However, in the case of landfarming, there was no change in soil quality after remediation. The soil quality indices calculated for landscaping also decreased the most in the soil washing because organic matter and pH decreased during the process. In the case of thermal desorption and landfarming, all the soil quality decreased due to contamination, but it increased slightly after remediation. The two indices applied in this study, SQIT and SQIA, showed similar trends, suggesting that both can be used for soil quality evaluation. Further research is needed on how much the soil quality evaluation results presented in this study can reflect the various services the soil ecosystem provides, that is, the actual soil functions in these soils.

Seismic equivalent linear response of a structure by considering soil-structure interaction: Analytical and numerical analysis

Maroua Lagaguine,Badreddine Sbartai 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.87 No.2

For a given structural geometry, the stiffness and damping parameters of the soil and the dynamic response of the structure may change in the face of an equivalent linear soil behavior caused by a strong earthquake. Therefore, the influence of equivalent linear soil behavior on the impedance functions form and the seismic response of the soil-structure system has been investigated. Through the substructure method, the seismic response of the selected structure was obtained by an analytical formulation based on the dynamic equilibrium of the soil-structure system modeled by an analog model with three degrees of freedom. Also, the dynamic response of the soil-structure system for a nonlinear soil behavior and for the two types of impedance function forms was also analyzed by 2D finite element modeling using ABAQUS software. The numerical results were compared with those of the analytical solution. After the investigation, the effect of soil nonlinearity clearly showed the critical role of soil stiffness loss under strong shaking, which is more complex than the linear elastic soil behavior, where the energy dissipation depends on the seismic motion amplitude and its frequency, the impedance function types, the shear modulus reduction and the damping increase. Excellent agreement between finite element analysis and analytical results has been obtained due to the reasonable representation of the model.

Estimation of the van Genuchten Parameters of Soil Water Retention Curve with RETC for Ap Horizon Soils of Different Soil Series in Reclaimed Tidal Flat Land

Kyo Suk Lee(이교석),Jin Hee Ryu(류진희),Doug Young Chung(정덕영) 한국토양비료학회 2021 한국토양비료학회 학술발표회 초록집 Vol.2021 No.11

Proper water management strategies are needed for reclaimed tidal flat soils with extremely low permeability, high salinity, and a lack of non-saline water resources. In this study, soil water retention curves were obtained from 150 soil samples collected from the Ap horizon of five soil series. The soil-water retention characteristics between 0 and 50 kPa and 50 and 1500 kPa were measured by the sandbox and kaolin-plate and the pressure chamber method. The estimated volumetric water content (θ<SUB>v</SUB>) was calculated by the van Genuchten (vG) equation using RETention Curve (RETC) based on the soil particle distribution and mean bulk density of all soil series. The mean measured saturated water content (θ<SUB>s</SUB>) and residual water content (θ<SUB>r</SUB>) at 0 and –1500 kPa were slightly higher in soil series with high clay contents (0.479 and 0.159 in Bokchun soil series) than in those with high sand contents (0.439 and 0.072 in Taehan soil series), indicating that measured θ<SUB>v</SUB> and θ<SUB>r</SUB> values were influenced by the soil particle distribution. However, the SD and SE suggested that measured θ<SUB>v</SUB> reflects the actual mean θ<SUB>v</SUB>. The RMSE, MBE, and R² of median, minimum, and maximum θ<SUB>v</SUB> led to the best fit of all soil samples for all soil series. These findings demonstrate the application of the vG model for the estimation of soil water retention in reclaimed tidal flat soils. Improved estimation of θs and θr is needed based on a larger dataset, including subsurface layers, which influence water retention characteristics.

Unsaturated Characteristics of Acid Sulfate Soils before and after Neutralization Treatment

송영석 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.12

Acid sulfate soils (ASSs) are naturally formed soils or sediments that are produced under waterlogged and poorly drained conditions. The sulfides can move to the surface water and into subsurface water and cause loss of nutrients in the soil and destroy the soil structure. To perform effective management of the ASSs located above and under the groundwater table, the unsaturated characteristics of ASSs before and after neutralization treatments should be investigated. An ASS was sampled from the natural soil layer around Ilkwang mine in Busan, South Korea, and CaCO3, which is a neutralizer, and polyacrylamide (PAM) which is a soil stabilizer, were mixed with the ASS in the neutralization treatment. The soil-water characteristics curves (SWCCs) and hydraulic conductivity functions (HCFs) of the drying-wetting processes of the ASS before and after the neutralization treatment were measured and assessed using the van Genuchten model. According to the assessment results of the SWCCs and HCFs, the matric suction of the ASS after the treatment was smaller than that before the treatment at the same volumetric water content (VWC). Additionally, the hydraulic conductivity of the ASS after treatment was larger than that before treatment at the same effective degree of saturation because the effective particle size of the ASS increased and the pore size among particles increased due to soil aggregation. It was confirmed that the neutralization treatment improved the hydrological properties of the ASS and the ASS after treatment may be utilized as sound materials for various fields.

교란 정도에 따른 토양 미소절지동물의 구성 및 날개응애류 군집 구조 비교

김지원 ( Ji Won Kim ),금은선 ( Eun Sun Keum ),정철의 ( Chul Eui Jung ) 한국토양동물학회 2011 한국토양동물학회지 Vol.15 No.1

An ecological disturbance is an event that often results in a prolonged disruption of ecosystem structure and function. This study was to relate the disturbance gradient to soil microarthropod compositions and orbatid mite communities. Soil Sample was taken from annual plant of milk vetch (Astragalus sinicus), perennial plant of grassland, and perennial nut pine (Pinus koraiensis). Mean abundance of soil arthropods were not significant different in grassland and nut pine. However, significant difference was found in milk vetch. Collembola was the dominant group (71%), which was followed by gamasid mites (10%) in highly disturbed site of milk vetch. In grassland with mid disturbance, abundance of oribatida, collembola, and gamasida was 66%, 30% and 4% respectively. In nut pine with low disturbance, collembola (34%), oribatid mite (26%) and gamasid mite (17%) was found. Abundance and species richness, diversity index of oribatid mite was very lower in high disturbance site. Oppiella acuminata and Boreozetes donghaksaensis was the dominant species in nut pine. Scheloribates sp. was dominant in grassland and only Ceratozetes mediocris was found in milk vetch. We shows that clear distinction of soil microarthropod abundance and composition as well as the community structure of the most dominant group of soil microarthropod, Oribatida relative to the disturbance gradient. Further study is demanded for the factorial influence on soil faunal behavior and functional aspect of soil faunal system relative to the disturbance and recovery process.

Sediment Erosion and Transport Experiments in Laboratory using Artificial Rainfall Simulator

Ram Krishna Regmi,Kwansue Jung,Hajime Nakagawa,Jaewon Kang,Giha Lee 한국지반환경공학회 2014 한국지반환경공학회논문집 Vol.15 No.4

Catchments soil erosion, one of the most serious problems in the mountainous environment of the world, consists of a complex phenomenon involving the detachment of individual soil particles from the soil mass and their transport, storage and overland flow of rainfall, and infiltration. Sediment size distribution during erosion processes appear to depend on many factors such as rainfall characteristics, vegetation cover, hydraulic flow, soil properties and slope. This study involved laboratory flume experiments carried out under simulated rainfall in a 3.0 m long × 0.8 m wide × 0.7 m deep flume, set at 17° slope. Five experimental cases, consisting of twelve experiments using three different sediments with two different rainfall conditions, are reported. The experiments consisted of detailed observations of particle size distribution of the out-flow sediment. Sediment water mixture out-flow hydrograph and sediment mass out-flow rate over time, moisture profiles at different points within the soil domain, and seepage outflow were also reported. Moisture profiles, seepage outflow, and movement of overland flow were clearly found to be controlled by water retention function and hydraulic function of the soil. The difference of grain size distribution of original soil bed and the out-flow sediment was found to be insignificant in the cases of uniform sediment used experiments. However, in the cases of non-uniform sediment used experiments the outflow sediment was found to be coarser than the original soil domain. The results indicated that the sediment transport mechanism is the combination of particle segregation, suspension/saltation and rolling along the travel distance.