• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.6
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• pp.77-87
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• 2012

Recently, Load and Resistance Factor Design (LRFD) based on reliability analysis has become a global trend for economical and rational design. In order to implement the LRFD, quantification of uncertainty for load and resistance should be done. The reliability of result relies on input variable, and therefore, it is important to obtain exact uncertainty properties of load and resistance. Since soil stress is the main reason causing the settlement or deformation of ground and load on the underground structure, it is essential to clarify the uncertainty of soil stress distribution for accurately predict the uncertainty of load in LRFD. In this study, laboratory model test on silty sand bed under probabilistic load is performed to observe propagation of upper load uncertainty. The results show that the coefficient of variation (COV) of soil stress are varied depending on location due to non-linear relationship between upper load increment and soil pressure increment. In addition, when the load uncertainty is transmitted through ground, COV is decreased by damping effect.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.261-273
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• 1993

In order to study hydraulic properties and mechanical properties on unsaturated region, soil-water retention curve was obtained for suction plate method and pressure plate method, respectively. To investigate permeability of unsaturated soil and soil-water retention curve at the same time, unsaturated permeability tests using an improved Richard's method were performed on Joomoonjin Sand. These experimental results were compared with those by empirical equations. The relationship between air entry value and saturated permeability of filter was obtained for selecting a proper filter in unsaturated soil tests.

• The Korean Journal of Ecology
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• v.18 no.1
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• pp.55-62
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• 1995

This study was conducted to investigate the distribution pattern of plants on streamside of Kyonganchon, which is a tributary of the Han River, and to determine the relationships between plant distribution and environmental factors. Fifteen study sites were selected along the Kyonganchon, and vegetation distribution pattern and soil environmental factors were determined. The most frequently ocurring species in the study sites were Persicaria thunbergii, Persicaria hydropiper, Echinochloa crus-galli and Bidens frondosa, and among them the two Persicaria species were dominants of the community. Many species showed different distribution along the stream:Chenopodium album, Equisetum arvense and Setaria viridies occurred in the upstream region, while Rumex crispus, Leonurus sibiricus and Rorippa islandica occurred in the middle and downstream regions. Analysis of soil properties showed that organic matter and clay content were higher in the upstream region while sand content was higher in the downstream region. The results of DCA ordination showed that axis one was positively correlated with organic matter and clay content and negatively correlated with sand content, indicating that the distribution pattern of vegetation along the Kyonganchon was determined by elevational gradient from upstream to downstream region or gradient of stream width and water level, and by soil organic matter content and soil texture related to these gradients.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.619-626
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• 2002

In this study, a correlation among pressure, time and quantity of injection was organized from the laboratory tests, which were executed many times representing in-situ soil conditions carefully and then it would be applied to the in-situ soil injection simulator which will be developed for optimal injection into the ground. The sort of sample soils were both sand(A specimen) and silty sand(B specimen). Injection tests were gone into operation by compaction state, injection velocity and the depth individually. In the ground improved with permeation Infection, the relation among injection pressure of the same depth, the injected quantities and time were systematic by the depth. By defining the limit range of injection pressure and quantity about the variety of a linear equation obtained from lining each of their trend, the application of laboratory injection monitoring program and the data to evaluate its realization were produced. In the ground improved with root type injection, the relation between injection pressure and the injected quantities was irregular because fracture state occurred quickly.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.9
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• pp.32-39
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• 2008

This paper presents the soil ionization phenomena and the parameters with the transient characteristics of model grounding system under lightning impulse voltages. lonization properties of dry and wet sands were investigated by using two test cells of concentric cylindrical electrode system with different dimensions. As a result non-linear electrical behavior of sand under high impulse voltage is caused by ionization process. The transient impedance of sand depends not only on the water content but also on the magnitude of applied impulse voltages. The grounding impedance is decreased with increasing the water content and the magnitude of a lied voltages. The results resented in this paper will provide useful information on the design of high performance grounding systems against lightning surge.

• Geomechanics and Engineering
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• v.24 no.2
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• pp.105-113
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• 2021

Deformations in soils induced by dynamic loads cause damage to the structures above the soil layers. It is important for geotechnical engineering practice that how the soil behaves due to repeated loads and the necessary precautions to be taken accordingly. Turkey is one of the most important seismic regions in Europe and earthquake studies to be conducted in this area are intended to reduce the damage as a result of taking the necessary measures. To determine the properties of soils under dynamic loads, stress-controlled dynamic triaxial and resonant column tests can be performed. In this study, these experiments were implemented in the laboratory on the clayey sand soil samples obtained from Bilecik Söğüt. To evaluate the effects of the confining pressure and rate of loading on the dynamic behavior of soils, samples were dynamically loaded by different rates at varying confining pressures. As a result, the changes in stress-strain properties of soils under dynamic loads were investigated. The alteration in behavior in terms of modulus reduction and damping ratios was obtained to vary a lot with the change of the lateral pressure on soil along with the frequency of the load.

• Geomechanics and Engineering
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• v.31 no.3
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• pp.291-304
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• 2022

Maximum shear modulus (G_max or G₀) is an important soil property useful for many engineering applications, such as the analysis of soil-structure interactions, soil stability, liquefaction evaluation, ground deformation and performance of seismic design. In the current study, bender element (BE) tests are used to evaluate the effect of the void ratio, effective confining pressure, grading characteristics (D₅₀, C_u and C_c), anisotropic consolidation and initial fabric anisotropy produced during specimen preparation on the G_max of sand-gravel mixtures. Based on the tests results, an empirical equation is proposed to predict G_max in granular soils, evaluated by the experimental data. The artificial neural network (ANN) and Adaptive Neuro Fuzzy Inference System (ANFIS) models were also applied. Coefficient of determination (R²) and Root Mean Square Error (RMSE) between predicted and measured values of G_max were calculated for the empirical equation, ANN and ANFIS. The results indicate that all methods accuracy is high; however, ANFIS achieves the highest accuracy amongst the presented methods.

• Geomechanics and Engineering
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• v.38 no.2
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• pp.165-177
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• 2024

Liquefaction phenomenon refers to a phenomenon in which excess pore water pressure occurs when a dynamic load such as an earthquake is rapidly applied to a loose sandy soil ground where the ground is saturated, and the ground loses effective stress and becomes liquid. The laboratory repetition test for liquefaction evaluation can be performed through a repeated triaxial compression test and a repeated shear test. In this regard, this study attempted to evaluate the effects of the relative density of sand on the liquefaction resistance strength according to particle size distribution using repeated triaxial compression tests, and additional experimental verification using numerical analysis was conducted to overcome the limitations of experimental equipment. As a result of the experiment, it was confirmed that the liquefaction resistance strength increased as the relative density increased regardless of the classification of soil, and the liquefaction resistance strength of the SP sample close to SW was quite high. As a result of numerical analysis, it was confirmed that the liquefaction resistance strength increased as the confining pressure increased under the same relative density, and the liquefaction resistance strength did not decrease below a certain limit even though the confining pressure was significantly reduced at a relatively low relative density. This is judged to be due to a change in confining pressure according to the depth of the ground. As a result of analyzing the liquefaction resistance strength according to the frequency range, it was confirmed that there was no significant difference from the laboratory experiment results in the basic range of 0.1 to 1.0 Hz.

• Journal of the Korean Geotechnical Society
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• v.37 no.12
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• pp.73-87
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• 2021

Pile-supported wharf is a structure that can transmit and receive cargo, and it is mainly installed on saturated inclined ground. In the seismic design of these structures, the codes suggest using the response spectrum analysis method as a preliminary design method. However, guideline on modeling method for pile-supported wharf installed in saturated soil is lacking. Therefore, in this study, the dynamic centrifuge model test and response spectrum analysis were performed to evaluate the seismic performance of pile-supported wharf installed into the saturated soil. For the test, some sections (3×3 pile group) among the pile-supported wharf were selected, and they were classified into two model (dry and saturated sand model). Then the response spectrum analysis was performed by using the soil spring method to the test model. As a result of test and analysis, the m om ent difference occurred within a m axim um of 51% in the dry sand m odel and the saturated sand model where liquefaction does not occur, and it was found that the pile moment by depth was properly simulated. Therefore, in the case of these models, it is appropriate to perform the modeling using the Terzaghi (1955) constant of horizontal subgrade reaction (n_h)

• Korean Journal of Soil Science and Fertilizer
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• v.28 no.4
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• pp.340-349
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• 1995

Effects of the zeolite particle size on the soil chemical properties and on rice growth was investigated on the pot with the loamy sand (Sadu series) and silty clay loam(Paju series) soils. All the zeolite treatments brought the increase of unhulled grain yield on the both loamy sand and silty clay loam soils. Unhulled grain yield increased with increasing the amount of zeolite applied and with decreasing the amount of particle size of zeolite applied on both soils. Unhulled grain yield increased significantly by 11.1% (22.79g/head) with 2ton/10a of smaller than $106{\mu}m$ size zeolite on the loamy sand soil and on the silty clay loam soil, yield increased by 9.3% (24.98g/head) with 1.5ton/10a of smaller than $106{\mu}m$ size zeolite. CEC, pH and contents of exchangeable cations of the soil after experiment were raised by increasing the amount of zeolite and also by decreasing the particle size of zeolite at both soil. At the heading stage, the zeolite treatments improved the growth of rice plant compared to control. The nutrient contents(T-N, Ca, Mg, K, Na), except phosphorus, in the rice plant grown on the zeolite treated soils were higher than control plot.