• Proceedings of the Korean Geotechical Society Conference
• /
• 1992.10a
• /
• pp.55-60
• /
• 1992

Hydraulically filled ground is formed by the settling of soil grains from the mixture of soil grains and water. It was generally known that the settling speed of the soil grains in governed by Stokes low. In the case of clayed dredged material, the shape of soil grains is not round, the surface of the soil grains is relatively large compared to the weight of soil grains and inter-grain ionic force is relatively large compared to the wight of soil grains. By this reason the settling and consolidation behavior of hydraulically filled quite different from that of Stokes law. This study investigated the settling and consolidation behavior of hydraulically filled materials of Yeochon industrial complex by large scale laboratory settling & consolidation container. The test results showed tat actual settling speed of soil grains in quite large compared to that of Stokes law. It was turned out that this phenomenon was due to the aggregation of soil grains. Also, it was truned out that the void ration and water content after the completion of settling process was 8.7 and 322% respectively. The consolidtion settlement of clayey hydraulic fill material was predicated better by "incremental small strain" consolidation concept than classical Terzaghj's consolidation concept (infinitesimal strain).

• Geotechnical Engineering
• /
• v.4 no.1
• /
• pp.37-48
• /
• 1988

This is a part of research projects to investigate the several significant statistical correlati- onships among the various physical and engineering properties of alluvial clayey deposits in the estuary area of the great fixe rivers through the South-West coastal districts where are expected to be developed as large ingustrial site or agricultual development projects. As a first trial, the statistical analyses through computer programs were carried out using the results of laboratory and field tests of 227 soil samples from the Seum-Jin river area. When the initial void ratio which plays crucial role to the settlement of foundation is more than 2.5, the compression indices of soil samples are remarkably scattered, but these indices, which are formulated as a general expression, tend to increase as increasing the clay content, liquid limit, plastic limit and initial void ratio.

• Geomechanics and Engineering
• /
• v.33 no.1
• /
• pp.1-9
• /
• 2023

The unconfined compression strength (UCS) of soils is commonly used either before or during the construction of geo-structures. In the pre-design stage, UCS as a mechanical property is obtained through a laboratory test that requires cumbersome procedures and high costs from in-situ sampling and sample preparation. As an alternative way, the empirical model established from limited testing cases is used to economically estimate the UCS. However, many parameters affecting the 1D soil compression response hinder employing the traditional statistical analysis. In this study, gene expression programming (GEP) is adopted to develop a prediction model of UCS with common affecting soil properties. A total of 79 undisturbed soil samples are collected, of which 54 samples are utilized for the generation of a predictive model and 25 samples are used to validate the proposed model. Experimental studies are conducted to measure the unconfined compression strength and basic soil index properties. A performance assessment of the prediction model is carried out using statistical checks including the correlation coefficient (R), the root mean square error (RMSE), the mean absolute error (MAE), the relatively squared error (RSE), and external criteria checks. The prediction model has achieved excellent accuracy with values of R, RMSE, MAE, and RSE of 0.98, 10.01, 7.94, and 0.03, respectively for the training data and 0.92, 19.82, 14.56, and 0.15, respectively for the testing data. From the sensitivity analysis and parametric study, the liquid limit and fine content are found to be the most sensitive parameters whereas the sand content is the least critical parameter.

• Journal of the Korean Geotechnical Society
• /
• v.30 no.3
• /
• pp.47-58
• /
• 2014

To investigate the unsaturated characteristics of the tailings obtained from the waste dump at Imgi mine, matric suction and volumetric water content were measured in both drying and wetting processes using Automated Soil-Water Characteristics Curve Apparatus. Based on the measured result, Soil Water Characteristic Curves (SWCC) were estimated by van Genuchten model. According to the unsaturated soil classification method, the tailings of the waste dump correspond to clayey sand. As a result of Suction Stress Characteristic Curve (SSCC) by Lu and Likos model, SSCC has a shape of S which is similar to SWCC. The hysteresis phenomenon occurred in SSCCs, which means the suction stress of drying path is larger than that of wetting path in the same effective degree of saturation. The effective stress of unsaturated soil is equal to that of saturated soil when matric suction is less than Air Entry Value (AEV). However, the effective stress of unsaturated soil is larger than that of saturated soil when matic suction is more than AEV. Meanwhile, unsaturated hydraulic conductivity by van Genuchten model decreased with increasing matric suction, and the hydraulic conductivity of drying path is larger than that of wetting path.

• Journal of the Korean GEO-environmental Society
• /
• v.10 no.2
• /
• pp.5-12
• /
• 2009

Soil samples from the King Sejong Station in Antarctic and Vladivostok were tested in the laboratory and specific gravity, compaction curve, grain size distribution were determined. The effect of temperature change on the thermal conductivity, unfrozen water content, compressive strength were investigated. In addition, the change of tensile strength with temperature of the soil from Vladivostok was measured. Samples for the compressive strength test and tensional strength test were prepared in a mould with a fixed volume to prevent swelling. Also the effects of temperature and water content change on those strength were compared. Results from the thermal conductivity test showed that thermal conductivity values for both soils was larger at temperatures below freezing than those above freezing. The unfrozen water content dropped rapidly within a temperature range of $0{\sim}-5^{\circ}C$ and then gradually decreased further $-20^{\circ}C$. Compressive strength test results showed various stress/deformation curves with a change in water content. Sandy soil of the King Sejong Station had a much larger strength than ice at an identical temperature, while clayey soil of Vladivostok had a smaller strength than ice in the initial stage, but showed a larger strength at temperatures belows $-15^{\circ}C$. Tensile strength tests revealed an increase in the strength with a decreasing temperature.

• Korean Journal of Soil Science and Fertilizer
• /
• v.18 no.3
• /
• pp.289-296
• /
• 1985

To clarify the soil characteristics and genesis of the clayey terrace soils distributed in Yeongcheon (inland region) and Yeongil (coastal region), 9 typifying pedons including a recent local deposits were studied. The physico-chemical properties found were summarized as follows; 1. The contents of available water of the terrace soils were ranged from 12.0 to 20.3%. They were increased with increaseing clay content up to 35%, and then decreased at clay content of 35 to 55%, but were maintained about 12 to 13% when the clay content exceeds 55%. 2. The amount of water stable aggregates in the surface soils were ranged from 55.0 to 81.1%, and were low in cultivated upland where water erosion were accelerated while high in the paddy where the double cropping were practiced. The index of aggregate in cultivated upland were higher in the surface soils but the paddy soils were higher in subsoils. 3. The colloidal reactions checked by the differences between pH in $0.01N-Na_2SO_4$ and $H_2O$ indicate exchangeable acidity to exchangeable neutrality, which means a sort of Red-yellow soil forming process had been prevailed during genesis of the terrace soils. 4. Cation exchange capacity of the clayey terrace soils were averaged about 15.8-20.2me/100g of fine earth and 35.6-52.6me/100g of clay. The rates of base saturation were 32.7 to 57.6% and the rates decreased with increasing the elevations of terraces. 5. The activities of free iron oxides were 0.061 to 0.739 and the values decreased with increasing elevation while the crystallinity index of iron oxides positively correlated with elevations the values ranged from 0.067 to 0.537.

• Korean Journal of Soil Science and Fertilizer
• /
• v.7 no.1
• /
• pp.17-21
• /
• 1974

This study was performed to find out the organic matter content, and what is more, the relation between its content and major morphological properties of cultivated upland soils in Korea. The results were as follows. 1. The average organic matter content of cultivated upland soils was 1.73 percent, mostly ranging from 0.6 to 2.5 percent. 2. Examining the organic matter content by subgroup of cultivated upland soils. It was found 13 percent in volcanic ash yellowish brown Cambisols and 6.3 percent in Humic yellowish brown Entisols, Fluventic yellowish brown Entisols was found 1.0 percent, lowest one. The average organic matter content of Entisols, Cambisols, and Argillisols was 1.1, 2.1, and 1.8 percent respectively. 3. According to organic matter content by texture of profile, the average content of sandy soils was 1.0 percent; 1.5 percent in coarse loamy soils; and 1.8 percent in fine loamy soils. The organic matter content increased with an increased clay content in coarse texture group, but there was no significant difference between fine loamy and clayey soil group. This tendency was also observed in surface soil texture. 4. In the relation between slope and organic matter content, its content in flat area was 1.3 percent that is rather low compared to 1.6 percent of sloping area. Especially, cultivated upland soils ranging brown 15 to 30 percent in slope were 1.8 percent which is relatively high. 5. The organic matter content have nothing to do with suitability groups. Itss ontent of I, II, III, IV and V class was 1.3, 1.6, 1.7, 1.2 and 2.0 percent respectively.

• Applied Biological Chemistry
• /
• v.20 no.1
• /
• pp.147-155
• /
• 1977

In this experiment, we expected yield increase depending on the control of ineffective tiller, heightening of effective tillering ratio and continuous supply of nitrogen until later growth stage of rice plant by deep layer split application. Treats were applied at Tongil and Jinheung variety, clayey loam and sandy loam soil, and drained and non-drained condition. Nitrogenous fertilizer application wab adopted as liquefied(50%) and lumped (50% and 80%) fertilizer at 12cm depth of soil before 35 days of rice heading time against the standard soil surface application. The results are summarized as follaw. 1. a. Jinheung showed great variant width of tiller numbers per rice plant growth stage, and low effective tillering ratio at soil surface dressing. But in the case of deep layer split application, the number of tiller increased normally, and effective tillering ratio was high. b. At Tonsil, the width of increase and decrease range of effective tiller number between soil surface dressing and deep layer split application was not so high as Jinheung. Deep layer split application of 80% lumped fertilizer showed maximum effective tillering ratio ($83%{\sim}93%$). C. In the case of Jinheung, it was supposed that deep layer split application of 80% lumped fertilizer was excessive nitrogen quantity. d. Effective tillering ratio was higher than Tonsil at Jinheung. 2. The number of grains per hill was increased by the deep layer split application, but the ripening ratio was decreased inversely with the increase of total grain number. 3. Length of top leaves was elongated at Jinheung by deep layer split application. It showed significant correlation between top leaves length and grain yield. 4. Deep layer split application inclosed N content of harvested straw. Yield and N content of straw showed possitive correlation. 5. The ratio of unhulled grain yield per straw weight was increased by deep layer splication. This ratio was higher at Jinheung than Tonsil. 6. Grain yield was appeared in order of 80% lumped fertilizer>50% lumped fertilizer>50% liquefied fertilizer>surface dressing by the deep layer split application. The yield increasing factors were the increasing of effective tillering ratio, number of panicles per hill and number of ripening grains per hill. 7. Grain yield was increased at Tongil in sandy loam soil and at Jinheung in clayey loam soil by deep layer split application. 8. The grain yield was increased at drained conditions of clayey loam soil and non-drained conditions of sandy loam soil. But in the case of 80% lumped fertilizer of deep layer split application at the sandy loam soil, the yield was not increased at non-drained conditions. 9. The effect of yield increase by deep layer split application comparing with the surface dressing was higher at Tonsil than ginheung, in spite of low ripening ratio of Tonsil caused by low temperature at heading and harvesting time.

• Korean Journal of Soil Science and Fertilizer
• /
• v.20 no.1
• /
• pp.23-28
• /
• 1987

A series of field and laboratory experiments were conducted to find out the changes of some soil chemical constituents in different soil depth with three different soil textures as Bongnam-clayey, Gwanghwal-silty loam and Mangyeong fine sandy soil on the assessment of reclamation duration in Fluvio-marine soil. The result obtained were summarized as follows; 1. Exchangeable potassium, calcium, magnessium, sodium with manganes, silica and cation exchange capacity were remarkably decreased with assessment of reclamation duration. Decreasing tendency was pronounced more in sandy soil than silty loam or clayly soil. 2. Soil organic matter content in top soil was increased with increasing of reclamation years. From reclamation time, about 30 years in clayly and about 80 years in silty loam and sandy soil were necessary for the maintanance of averaged organic matter content to 2.5%. 3. Potassium activity ratio ($K/{\sqrt{Ca+Mg+Na}}$) was differed with soil depth, soil texture and assessment of reclamation duration. About 50 years is may be necessary for the maintanance of potassium activities ratio in ordinary paddy soil of 0.05-0.2. 4. Percent of adsorbed sodium (PAS), ratio of adsorbed sodium (RAS) and ratio of sodium adsorbtion(RSA) were remarkably decreased with assessment of reclamation duration. Specially, decreasing tendency was pronounced more in sandy soil than silty loam and clayly soil 5. Amount of clay content in subsoil was appearently decreased during 30 years of reclamation, but clay contents in top soil was appearently decreased 50 years after reclamation.

• Korean Journal of Soil Science and Fertilizer
• /
• v.16 no.1
• /
• pp.1-6
• /
• 1983

The results of COLE(Coefficient of Linear Extensibility) measurement on various paddy soils in Korea are summarized as follows; 1. The COLE values of paddy soil in Korea varied from 0.024 to 0.094 in the surface soil while in the sub-surface soils those were ranging from 0.022 to 0.115. The poorer the relative drainage and the finer the texture caused, the greater the COLE values. 2. The matured clayey soils on fluvio-marine plains and local alluvium derived from the Tertiary materials have COLE values more than 0.09 which is demonstrated that the necessity of COLE measurement throughout profiles so that could be considered the characteristic in the characteristic of those soils. 3. The clay content has the highest positive correlation (r=0.81~0.76) values. The content of organic matter, water content at 1/3 bar, Atterberg limits, water stable aggregate etc. also have significant positive correlation with COLE values while the context of sand and silt show negative correlation. 4. Although the COLE values measured on horizontal linear bases were slightly greater than those measured on volume bases practicability was for granted. For more accurate measurement of COLE, it is reasonable to have the average values of COLE calculated from the horizontal and vertical bases.