• Geotechnical Engineering
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• v.8 no.2
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• pp.5-20
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• 1992

The physical-based and lumped-parameter hydrologic groundwater flow model for predicting the rainfall-triggered rise of groundwater levels in hillside slopes is developed in this paper to assess the risk of landslides. The developed model consists of a vertical infiltration model for unsaturated zone linked to a linear storage reservoir model(LSRM) for saturated zone. The groundwater flow model has uncertain constants like soil depttL slope angle, saturated permeability, and potential evapotranspiration and four free model parameters like a, b, c, and K. The free model parameters could be estimated from known input-output records. The BARD algorithm is uses as the parameter estimation technique which is based on a linearization of the proposed model by Gauss -Newton method and Taylor series expansion. The application to examine the capacity of prediction shows that the developed model has a potential of use in forecast systems of predicting landslides and that the optimal estimate of potential 'a' in infiltration model is the most important in the global optimum analysis because small variation of it results in the large change of the objective function, the sum of squares of deviations of the observed and computed groundwater levels. 본 논문에서는 가파른 산사면에서 산사태의 발생을 예측하기 위한 수문학적 인 지하수 흐름 모델을 개발하였다. 이 모델은 물리적인 개념에 기본하였으며, Lumped-parameter를 이용하였다. 개발된 지하수 흐름 모델은 두 모델을 조합하여 구성되어 있으며, 비포화대 흐름을 위해서는 수정된 abcd 모델을, 포화대 흐름에 대해서는 시간 지체 효과를 고려할 수 있는 선형 저수지 모델을 이용하였다. 지하수 흐름 모델은 토층의 두께, 산사면의 경사각, 포화투수계수, 잠재 증발산 량과 같은 불확실한 상수들과 a, b, c, 그리고 K와 같은 자유모델변수들을 가진다. 자유모델변수들은 유입-유출 자료들로부터 평가할 수 있으며, 이를 위해서 본 논문에서는 Gauss-Newton 방법을 이용한 Bard 알고리즘을 사용하였다. 서울 구로구 시흥동 산사태 발생 지역의 산사면에 대하여 개발된 모델을 적용하여 예제 해석을 수행함으로써, 지하수 흐름 모델이 산사태 발생 예측을 위하여 이용할 수 있음을 입증하였다. 또한, 매개변수분석 연구를 통하여, 변수 a값은 작은 변화에 대하여 목적함수값에 큰 변화를 일으키므로 a의 값에 대한 최적값을 구하는 것이 가장 중요한 요소라는 결론을 얻었다.

• Journal of Korea Water Resources Association
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• v.53 no.9
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• pp.637-646
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• 2020

The shallow landslide-trigerred debris flow in hillslope catchments is the primary geological phenomenon that drives landscape changes and therefore imposes risks as a natural hazard. In particular, debris flows occurring in urban areas can result to substantial damages to properties and human injuries during the flow and sediment transport process. To alleviate the damages as a result of these debris flow, analytical models for flow and damage prediction are of significant importance. However, the analysis of debris flow model parameters is not yet sufficient, and the analysis of the entrainment, which has a significant influence on the flow process and the damage extent, is still incomplete. In this study, the effects of erosion and erosion process on the flow and the impact area due to the change in the soil parameters are analyzed using Deb2D model, a flow analysis model of debris developed in Korea. The research is conducted for the case of the Mt. Umyeon landslide in 2011. The resulting impacted area, total debris-flow volume, maximum velocity and inundated depth from the Erosion model are compared to the field survey data. Also, the effect of the entrainment changing parameters is analyzed through the erosion shape and depth. The debris flow simulation for the Raemian and Shindong apartment catchment with the consideration of entrainment effect and erosion has been successful. Each parameter sensitivity could be analyzed through sensitivity analysis for the two basins based on the change in parameters, which indicates the necessity of parameter estimation.

• Journal of the Korean Geosynthetics Society
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• v.21 no.1
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• pp.1-10
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• 2022

In this study, a model parameter evaluation method using relative density was proposed to utilize applicable UBC3D-PLM for liquefaction behavior. In addition, dynamic effective stress analysis, that is, liquefaction analysis, was performed on the case of the liquefaction occurrence region where acceleration and pore water pressure were measured, and compared with the actual measurement and the existing Finn analysis results. Through this study, it was found that the proposed method can easily evaluate the necessary parameters required by the related model and predict the pore water pressure behavior in the region where liquefaction occurs. In addition, in the case of the study area, both measurements and numerical analysis showed that liquefaction occurred when a certain amount of time elapsed after the earthquake acceleration reached the maximum value. In the case of UBC3D-PLM applied in this study, the excess pore water pressure behavior similar to the actual measurement was predicted, and the occurrence of liquefaction was evaluated in the same way as the actual measurement. In particular, although the excess pore water pressure in the sand layer was greater, the phenomenon in which liquefaction occurred in the silt layer was accurately realized. It is expected that the proposed model parameter evaluation method and finite element analysis applying UBC3D-PLM can be used to select the liquefaction reinforcement region in the future seismic design and reinforcement by evaluating the liquefaction occurrence region similarly to the real one.

• Journal of Korea Water Resources Association
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• v.56 no.8
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• pp.509-520
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• 2023

Various drought indices are widely used for assessing drought conditions which are affected by many factors such as precipitation, soil moisture, and runoff. The values of drought indices varies depending on hydro-meteorological data and calculation formulas, and the judgment of the drought condition may also vary. This study selected four calculation components such as precipitation data length, accumulation period, probability distribution function, and parameter estimation method as the sources of uncertainty in the calculation of standardized precipitation index (SPI), and evaluated their contributions to the uncertainty using root mean square error (RMSE) and linear mixed model (LMM). The RMSE estimated the overall errors in the SPI calculation, and the LMM was used to quantify the uncertainty contribution of each factor. The results showed that as the accumulation period increased and the data period extended, the RMSEs decreased. The comparison of relative uncertainty using LMM indicated that the sample size had the greatest impact on the SPI calculation. In addition, as sample size increased, the relative uncertainty related to the sample size used for SPI calculation decreased and the relative uncertainty associated with accumulation period and parameter estimation increased. In conclusion, to reduce the uncertainty in the SPI calculation, it is essential to collect long-term data first, followed by the appropriate selection of probability distribution models and parameter estimation methods that represent well the data characteristics.

• Geotechnical Engineering
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• v.14 no.3
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• pp.25-46
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• 1998

This paper shows that there are the results of a series of model tests on the behavior of single pipe pile which is subjected to lateral load in, Nak-dong River sand. The purpose of the present paper is to estimate the effect of Non-homogeneity. constraint condition of pile head, lateral load velocity, relative density, and embedded length of pile on the behavior of single pile. These effects can be quantified only by the results of model tests. Also, these are compared with the results of the numerical methods (p-y method, modified Vlasov method; new ${\gamma}$ parameter, Characteristic Load Method'CLM). In this study, a new ${\gamma}$ parameter equation based on the Vlasov method was developed to calculate the modulus of subgrade reaction (E. : nhz.) proportional to the depth. The p-y method of analysis is characterized by nonlinear behavior. and is an effective method of designing deep foundations subjected to lateral loads. The new method, which is called the characteristic load method (CLM). is simpler than p-y analysis. but its results closely approximates p-y analysis results. The method uses dimensional analysis to characterize the nonlinear behavior of laterally loaded piles with respect to be relationships among dimensionless variables. The modulus of subgrade reaction used in p-y analysis and modified Vlasov method obtained from back analysis using direct shear test (DST) results. The coefficients obtained from DST and the modified ones used for the prediction of lateral behavior of ultimate soil reaction range from 0.014 to 0.05. and from 0.2 to 0.4 respectively. It is shown that the predicted numerical results by the new method (CLM), p-y analysis, and modified Vlasov method (new parameter) agree well with measured results as the relative density increases. Also, the characteristic load method established applicability on the Q-Mnu. relationship below y/D=0.2.

• Korean Journal of Soil Science and Fertilizer
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• v.8 no.1
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• pp.1-17
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• 1975

Laboratory experiments on the phosphorus adsorption by soil were conducted to evaluate the parameters for determination of phosphorus adsorption capacity of soil, which serve as a basis for establishing the amount of phosphorus required to improve newly reclaimed soil and volcanic ash soil. The calculated Langmuir adsorption maxima varied from 6.2-32.9, 74.7-90.4 and 720-915mg p/100g soil for cultivated soils, non-cultivated soils, and volcanic ash soils respectively. The phosphorus absorption coefficient ranged from 116-179, 161-259 and 1,098-1,205mg p/100g soil for cultivated soils, non-cultivated soils, and volcanic ash soils respectively. The ratio of the phosphorus absorption coefficient to Langmuir adsorption maximum was low in soils of high phosphorus adsorption capacity (1.3-1.5) and high in soils of low phosphorus adsorption capacity (2.2-18.7). Changes in the amount of phosphurus adsorption induced by liming and preaddition of phosphorus were hadly detected by the phosphorus absorption coefficient, which is measured using a test solution with a relatively high phosphorus concentration. The Langmuir adsorption maximum was a more sensitive index of the phosphorus adsorption capacity. The Langmuir adsorption maxima of the non-cultivated soils, which were treated with an amount of calcium hydroxide equivalent to the exchangeable Al and incubated ($25-30^{\circ}C$) for 40 days at field capacity, were lower than the original soils. The change in the adorption maximum on incubation following the liming of soils was insignificant for other soils. The secondary adsorption maximum of soils, which received phosphorus equivalent to the Langmuir adsorption maximum of the limed soils incubated ($25-30^{\circ}C$) for 50 days at held capacity, was 74.5, 5.6 and 23.8% of the primary adsorption maximum for volcanic ash soils, non-cultivated soils, and cultivated soils respectively. The amount of phosphorus adsorbed by soils increased quadratically with the concentration of phosphorus solution added to the soils. The amount of phosphorus adsorbed by 5-g soil samples from 100ml of 100- and 1,000mg p/l solution for the mineral soils and volcanic ash soils respectively was found to be close to the Langmuir adsorption maximum. The amount of the phosphorus adsorbed at these concentrations is defined as a saturation adsorption maximum and proposed as a new parameter for the phosphorus adsorption capacity of the soil. The evaluation of the phosphorus adsorption capacity by the saturation adsorption maximum is regarded as a more practical method in that it obviates the need for the various concentrations used for the determination of the Langmuir adsorption maximum.

• Geotechnical Engineering
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• v.6 no.1
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• pp.7-14
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• 1990

The two degree of freedom model is proposed to study the effects of imperfect fixing at the active end of spring-top resonant column apparatus. A computer program using the SYMPHONY spreadsheet is developed to calculate the dimensionless frequency, F, from which modulug can be determined. It is found that the effect of reaction mass through the parameter Tr on dimensionless frequency, F, can not be ignored if Tr$\leq$20. As To increases, the variation of F increases. But for Tr$\geq$ 20, the effect of To becomes small. It is recommended that T. be greater than 20 if single degree of freedom model is rosed to determine modulus of soil. It also is found that damping ratios of specimen and apparatus do not strongly affect the dimensionless frequency, F.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.4
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• pp.9-19
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• 2014

The objective of this study was to evaluate of the Tank model in simulating runoff discharge from rural watershed in comparison to the SWAT (Soil and Water Assessment Tool) model. The model parameters of SWAT was calibrated by the shuffled complex evolution-university Arizona (SCE-UA) method while Tank model was calibrated by genetic algorithm (GA) and validated. Four dam watersheds were selected as the study areas. Hydrological data of the Water Management Information System (WAMIS) and geological data were used as an input data for the model simulation. Runoff data were used for the model calibration and validation. The determination coefficient ($R^2$), root mean square error (RMSE), Nash-Sutcliffe efficiency index (NSE) were used to evaluate the model performances. The result indicated that both SWAT model and Tank model simulated runoff reasonably during calibration and validation period. For annual runoff, the Tank model tended to overestimate, especially for small runoff (< 0.2 mm) whereas SWAT model underestimate runoff as compared to observed data. The statistics indicated that the Tank model simulated runoff more accurately than the SWAT model. Therefore the Tank model could be a good tool for runoff simulation considering its ease of use.

• Clean Technology
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• v.3 no.2
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• pp.57-73
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• 1997

Metal cleaning process is a technology which removes oil, dust and soil etc. on the surface of metal utilizing cleaning agents. These contaminants disturb the following processes such as plating and painting etc. if they are not removed. Thus, metal cleaning is typically an environmentally hazardous activity. Until recently, vapor degreasers as utilizing chlorinated solvents have been relatively cheap, extraordinarily versatile and waste disposal costs have been perceived as insignificant. Today, however, it is readily apparent that Industry's reliance upon chlorinated solvents as metal cleaners have resulted in a myriad of environmental, health and safety concerns. Therefore, this paper studies on a parameter and a sort of the alternative cleaning agents for the optimum cleaners. Also, a great deal of effort has been devoted to developing alternative metal cleaning technologies in advanced countries and some processes are being commercialized among them. We are going to consider alternative aqueous cleaning agents replacing organic chlorinated solvents and to pursue a domain application through a successful improvement case.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.9
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• pp.67-74
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• 2009

For the surge currents like lightning currents containing high frequency components and the abnormal currents having high frequencies which cause the EMI(Electromagnetic interference) problems for the electronic devices and communication instruments, the linear grounding electrodes have the significantly composite impedance characteristics which are dependent on the frequency of the applied current. The impedance of a grounding electrode is not lowered by expanding the dimension of the grounding electrode, and the length of grounding electrode having the minimum value of the grounding impedance for each condition of frequency and soil characteristics is existent, and it is defined as Critical length. In this paper, the critical lengths for the vertically and horizontally-buried grounding electrodes are calculated by using the distributed parameter circuit model. The propriety of the simulations has been confirmed by comparing the simulated results with the measured results.