• Journal of the Korean Geotechnical Society
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• v.34 no.5
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• pp.53-63
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• 2018

Dynamic soil-pile interaction is the main concern in the design of group piles under earthquake loadings. The lateral resistance of the pile group under dynamic loading becomes different from that of a single pile due to the group pile effect. However, this aspect has not yet been properly studied for the pile group under seismic loading condition. Thus, in this study the group pile effect was evaluated by performing a series of dynamic centrifuge tests on $3{\times}3$ group pile in dry loose sand. The multiplier coefficients for ultimate lateral resistance and subgrade reaction modulus were suggested to obtain the p-y curve of the group pile. The suggested coefficients were verified by performing the nonlinear dynamic analyses, which adopted Beam on Nonlinear Winkler Foundation model. The predicted behavior of the pile group showed the reasonable agreement compared with the results of the centrifuge tests under sinusoidal wave and artificial wave.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.1
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• pp.109-115
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• 2008

Malfunction of gutter systems in the slope area accelerate to percolate surface flow into underground and to cause the decrease of soil strength, Overflowing from gutter causes soil erosion from slope surface, secondary it is one of the main reasons to cause disaster in the hillside area. Much researches were reported and are undergoing about flood disaster in the down stream area, but rare in the upper reach(hillside). It is considered that improving function of gutter in the hillside is very important to prevent the disaster caused by rainfall. In this paper, After analyzing relationship between rainfall and disaster on the hillside in Busan, researches about having surface flow run into gutter effectively and preventing from overflowing outside of gutter on the hillside in Busan were carried out. Improved design methods of gutter are suggested to mitigate disaster in the sloping area by analysis of collected data and hydraulic model test.

• Economic and Environmental Geology
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• v.41 no.4
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• pp.443-451
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• 2008

Memon(1995) pointed out that the groundwater recharge from the precipitation is affected by various factors such as the occurrence, intensity, duration, and seasonal distribution of rainfall; air temperature, humidity, and wind velocity; the character and thickness of the soil layer above the water table; vegetated cover, soil moisture content, depth to the water table, topography; and land use. To reflect above factors, groundwater recharge in Chungju basin is computed by using the SWAT-K which is a longterm continuous watershed hydrologic model. Frequency analysis is adopted to evaluate the existing values of potential amount of groundwater development which is made by the 10 year drought frequency rainfall multiplied by recharge coefficient. In this work, the recharge rates of 10 year drought frequency in subbains were computed and compared with the existing values of potential amount of groundwater development. This process could point out the problems of existing precesses used for computing potential amount of groundwater development.

• Journal of Soil and Groundwater Environment
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• v.8 no.1
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• pp.81-86
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• 2003

Understanding the penetration behavior of the spilled oil is very important to remove itself and to minimize its impact on intertidal biological communities by earlier treatment of the oil. The purpose of this study is to clarify the effects of wave and tidal actions on the penetration of spilled oil and to evaluate main factors of oil penetration using a sandy-beach model. Infiltration processes into the sediments showed significant difference between seawater and crude oil. Seawater was infiltrated by both wave action and tidal fluctuation into the sediments in sandy beach. However, spilled crude oil penetrated into the sediments only by falling tides and not by wave action, and the first tide is most important for the penetration of stranded oil. Over 70% of bulk fraction in penetrated crude oil was concentrated to the top 2 cm sediment-layer when spilled oil volume was 1 L/$\textrm{m}^2$. Moreover, the penetration of stranded oil into the sandy beach sediments was strongly correlated with the oil viscosity affected by temperature.

• Journal of Korea Water Resources Association
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• v.51 no.7
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• pp.585-597
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• 2018

This study aims to investigate the variation of water quality and discharge under the condition of climate change and Best Management Practices (BMPs), which is one of the reduction methods for non-point source pollution. Soil and Water Assessment Tool (SWAT) model is applied to case in Cheongmicheon watershed. The coefficients required for SWAT model were calibrated using SWAT Calibration and Uncertainty Program. Climate change is considered by using Representative Concentration Pathway (RCP) scenarios, RCP 4.5 and RCP 8.5. It is known from simulation results that the non-point source pollutant increases under the climate change scenario assuming worse condition. It is also found in this study that an appropriate application of BMPs is able to reduce the quantity and temporal variation of non-point source pollutant effectively.

• Journal of Korea Water Resources Association
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• v.34 no.2
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• pp.131-140
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• 2001

The present study is focused on improving the methodology for the determination of parameters involved in USLE(Universal Soil Loss Equation) based on distributed system concept and investigation of sediment delivery ratio. Generally the distributed system concept consists of grid networks throughout the watershed and sediment can be traced from grid to rid in the direction of the steepest descent. The sediment yield data together with physical data of 10 small irrigation reservoirs in Kyounggi-Do are collected. After the sediment delivery ratio of a grid is defined to be related tothe fraction of forested or covered with delivery proofing area of the grid, the preportionality coefficient(C$_1$) is introduced. The distributed system model is calibrated using the available data for 8 reservoirs and is verified with the data for the ramaining 2 reservoirs, and regression analysis is made to express the proportionality coefficient $C_1$ in terms of watershed physical characteristics. By applying this results the verification of the distributed system model for 2 reservoirs showed a fair result, which justifies the applicability of the proposed method in the present study.

• Journal of the Korean Geotechnical Society
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• v.34 no.2
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• pp.5-17
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• 2018

In this study, the in-situ stress, strength and stress-strain characteristics with shear parameters (UU, CU, ${\bar{CU}}$) are analytically evaluated and the stability analyses are carried out under loading/unloading conditions. The in-situ stress and the stress-strain behaviour may become different according to input shear parameters in finite element analyses with construction step, Especially, if the internal friction angle in Mohr-Coulomb model is set to zero, the in-situ stress and the stress-strain behaviour might not be properly predicted. The results from CU parameter of total stress analysis have no significant difference with the results from CU of effective stress analysis. Therefore, in the numerical analysis for soft ground, CU parameters can be applied to predict in-situ stress and stress-strain behaviors. In addition, the calculation method was proposed to determine the shear parameter of Mohr-Coulomb model, which is corresponding to the shear strength equivalent to that of in-situ soil.

• Advances in environmental research
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• v.6 no.1
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• pp.67-81
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• 2017

Mining activities play a significant role in environmental pollution by producing large amounts of tailings which comprise heavy metals. The impressive increase in mining activities in recent decades, due to their high influence on the industry of developing countries, duplicates the need for a substantial effort to develop and apply efficient measures of pollution control, mitigation, and abatement. In this study, our objective was to investigate the effect of simulation of the leachate, pH and inflow intensity of transport of $Pb^{2+}$, $Zn^{2+}$, and $Cd^{2+}$ through Lakan lead and zinc plant tailings, in Iran, and to evaluate the modeling efficiency by comparing the modeling results and the results obtained from previous column studies. We used the HP1 model and the PHREEQC database to simulate metals transport through a saturated soil column during a 15 day time period. The simulations assumed local equilibrium. As expected, a lower pH and inflow intensity increased metal transport. The retardation of heavy metals followed the order $Zn^{2+}$ > $Pb^{2+}$ > $Cd^{2+}$ and the removal concentrations of Cd, Pb, and Zn at the inflow intensity critical scenario, and Cd and Pb at inflow acidity critical scenario exceeded the allowable EPA and Iranian's 1053 standard thresholds. However, although the simulation results generally agreed well with the results of the column study, improvements are expected by using multi-dimensional models and a kinetic modeling approach for the reactions involved. The results of such investigations will be highly useful for designing preventative strategies to control reactive transport of hazardous metals and minimize their environmental effects.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.5
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• pp.542-548
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• 2015

This study investigated methane productions and a degradation rate of organic matters by German standard method, VDI4630 test. In this study, 4 livestock byproducts from livestock farm were selected for the investigation. The objective of this study was to estimate a distribution of organic matters by using the double first-order kinetics model in order to calculate the rate of biodegradable organic matters which degrade rapidly in the initial stage and the persistently biodegradable organic matters which degrade slowly later. As a result, all the byproducts applied in this study showed rapid decomposition in the initial stage. Then the decomposition rate began to slow down for a certain period and the rate became 5 times slower than the initial decomposition rate. This trend of decomposition rate changes is typical conditions of organic matter decompositions. The easily degradable factors ($k_1$) ranged between $0.145{\sim}0.257day^{-1}$ and persistent degradable factors ($k_2$) were $0.027{\sim}0.080day^{-1}$. Among these results, greater organic matter decomposition rates from VDI4630 had greater $k_1$ values (0.257, $0.211day^{-1}$) and smaller $k_2$ values (0.027, $0.030day^{-1}$) for dairy wastewater and forage byproduct, respectively.

• Geomechanics and Engineering
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• v.28 no.3
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• pp.265-281
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• 2022

A set of slurry shield test system capable of cutter cutting and slurry automatic circulation is used to investigate the deformation characteristics, the evolution characteristics of support resistance and the distribution and evolution process of earth pressure during excavating and collapsing of slurry shield tunneling in circular-gravel layer. The influence of cover-span ratio on surface subsidence, support resistance and failure mode of excavation face is also discussed. Three-dimensional numerical calculations are performed to verify the reliability of the test results. The results show that, with the decrease of the supporting force of the excavation face, the surface subsidence goes through four stages: insensitivity, slow growth, rapid growth and stability. The influence of shield excavation on the axial earth pressure of the front soil is greater than that of the vertical earth pressure. When the support resistance of the excavation face decreases to the critical value, the soil in front of the excavation face collapses. The shape of the collapse is similar to that of a bucket. The ultimate support resistance increase with the increase of the cover-span ratio, however, the angle between the bottom of the collapsed body and the direction of the tunnel excavation axis when the excavation face is damaged increase first and then becomes stable. The surface settlement value and the range of settlement trough decrease with the increase of cover-span ratio. The numerical results are basically consistent with the model test results.