• Geotechnical Engineering
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• v.14 no.4
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• pp.33-46
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• 1998

Anisotropy of stiffness, from extremely small strains to post-failure strains, of isotropically consolidated air-pluviated sands in plane strain compression was studied by using the newly developed instrumentation for small strain measurements. Seven types of sand of the world-wide origins were tested, which have been extensively used for research purposes. Stress-strain at the specimen boundaries. It was found that the maximum Young's modulus $E_{max}$ was irrespective of the angle $\delta$ of the $\delta_1$ direction relative to the bedding plane. However, the normalized$ E_{max}$ was varied with the types of sand. Furthermore, the dependency of the strain and stress level on the stiffness was increased as $\delta$ decreased.

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.589-599
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• 2007

For the preliminary judgement on the chemical stability of concrete aggregates mixed with cement paste, ASTM C 295 method can be applied prior to the long-term chemical test methods. By using this standard test method, the petrographic study on the appropriateness of natural KEDO aggregates for concrete was carried out. With the natural gravel and sand aggregates, the polarized microscope, stereoscopic microscope, and X-ray diffractometer were used for examination. The result shows the 23% of gravel aggregates and 5.1% of sand aggregates are chemically unstable. To select the favorable KEDO concrete aggregates, it is required to exclude the highly metamorphosed rocks, acidic volcanic rocks, highly foliated rocks, and expansive rocks identified from mortar-bar test. Further chemical test and mortar-bar test method integrated with this study is recommended for the suitability assessment of natural KEDO concrete aggregates.

• Geotechnical Engineering
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• v.14 no.1
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• pp.59-70
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• 1998

Samples of silty sands and hydraulic fill ground were investigated by dynamic triaxial teats in order to evaluate the liquefaction strengths. In the tests, (1) undisturbed and disturbed samples were prepared, (2) dynamic shear strengths were measured under isotropic and anisotropic condition, and (3) the test results were compared with the other results which were tested by domestic and foreign researchers. The liquefaction shear strengths under ismtropic test condition were presented in terms of the relative densities. The amount of silt under 30o hardly influenced on the liquefaction strength. In the test results of anisotropically consolidated samples the liquefaction strength was dependent on the magnitude of the effective consolidation ratio. These teat results show that the liquefaction strength of the silty sand in Korea went coast exists within the boundary of the values suggested by Seed and Peacock(1971).

• Asian Journal of Turfgrass Science
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• v.17 no.1
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• pp.13-17
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• 2003

This study was conducted to figure out the effect of KOB Soil on creeping bentgrass‘Cobra’, Kentucky bluegrass (KB)‘Midnight’75% + Perennial ryegrass (PR)‘Palmer III’25%. This experiment was conducted from September 1, 2001 to August 31, 2002 at Hwajoulryong in Jeongsun County, Gwangwon-do. Treatments were Sand 80% + Peatmoss 20%, Sand 80% +KOB-Soil (No. 1) 20%, and Sand 80% +KOB-Soil (No. 2) 20%. Treatments with KOB Soils was superior to control fer the leaf length, number of leaf, turf quality and root length in Creeping bengrass and Kentucky bluegrass + Perennial ryegrass.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.4
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• pp.509-515
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• 2010

In this paper, the mechanism that can walk efficiently in wet land or sand area is proposed. A vision camera is attached to the mechanism, which makes a kind of biologically inspired robot for coast guard. This visionary information enables the biologically inspired robot to react in peripheral environment by a soft-computing algorithm. In addition, the biologically inspired robot can achieve the mission appointed by a programmer connecting with outside, based on RF and Blue-tooth communication module. Therefore, the purpose of this research is the implementation of the biologically inspired robot that can operate most adaptively in sand and wet surface based on Theo Jansen mechanism.

• Journal of the Korean GEO-environmental Society
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• v.12 no.2
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• pp.23-33
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• 2011

In this paper, we got soil-water characteristic curve(SWCC) of Nak-Dong River's sand respectively as relative density 40%, 60%, 80% and content of silt 0%, 10%, 20%, 30%. As a result, the more the sand densify in the same silt content and the more the sand has silt in the same relative density, the change of volume water content was decreased. we have known effect of silt contents for SWCC and verified existing empirical formula of SWCC. As experiment results of soil-water characteristic curves compared to the empirical solutions, the results of van Genuchten(1980) and Fredlund & Xing(1994) were well-matched showing S type curves with experiment results. Especially the empirical solution of Fredlund & Xing showed almost same results of the coefficient of correlation($R^2$) equal to 0.99.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.3
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• pp.217-226
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• 2003

This study is focused on the finding out load transfer mechanism in the ground near the tunnel during tunnel excavation in the jointed sandy ground. Laboratory model tests were performed on various cases of the overburden heights above tunnel crown, location, and degree of discontinuity planes. For model tests, a movable plate was installed in the midst of the bottom of sandy ground. This plate, moving downwards, was intended to model the stress relaxation during tunnel excavation. The load transfer was measured at the fixed separated bottom plates adjacent to the movable plate. As the result, the loosening zone and the load-transfer form around the tunnelling site were affected by the overburden height and the characteristics of discontinuous planes. And large loosening zone was developed along the discontinuous planes which were close to the tunnel.

• Journal of Wetlands Research
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• v.12 no.3
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• pp.57-65
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• 2010

This study was conducted to present primary data on the change of the physical characteristics of reservoir sediments for understanding the sedimentation. The records of the annual summation of the precipitation of >50mm per day (AP50) were compared with changes of bulk density, organic matter, mean grain-size, and sand ratio in sediment cores sampled from three reservoirs without dredging record. Reservoir sediments, characterized by mineral soil, contained organic matters originated from the debris of terrestrial plants, and changes of organic matter were related to changes of grain-size flowing into reservoirs when sediments of fine sandy loam showed 10% of organic matter contents. Rapid changes of grain-size and sand ratio in the sediment cores were associated with the increase and decrease of precipitation, and fluctuation of water level and water flow in reservoirs might have influenced on the formation of sediments in reservoirs. Records of AP50 suggested that sediments could accumulate more than about 30 within the short period of 10 years. The accumulated sediments in a short time can reflect the effect of natural and anthropogenic events on the physical characteristics of sediments.

• Journal of Bio-Environment Control
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• v.12 no.1
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• pp.38-44
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• 2003

This work was conducted to estimate amounts of irrigating water during the growing periods of pepper after estimating water consumption in the plastic film house in 1997 and 1998. Evapo-transpiration (ET) under conditions of a black and white PE mulch and sandy or clay loam soil which enhanced the growth and yield of red peppers was greater than that at the bare and sand soil. Average ET of pepper grown in pots accounted for 56.5%∼79.7% of total supplying water in 1997 and 1998. Most of ET was proportioned to the transpiration amount (91∼94%), but there was some difference between amounts of ET and transpiration plus evaporation. Although 57 depended on conditions of the soil texture and plant growth, transpiration for pepper growing periods was amounted to 337.7∼774.3 m in the clay soil,910.6 m in the sandy loam soil, and 253.1 mm in the sandy soil.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.3
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• pp.63-69
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• 1983

A theoretical equation is presented to estimate the lateral earth pressures acting on piles in a row in cohesionless soil. Then, a series of model tests are carried out for various kinds of pile diameters and pile intervals, followed by very good agreements between the experimental and theoretical values of the lateral earth pressures on piles. The experimental results prove the validity of an assumption on the plastic condition of soil around piles set up in the theoretical derivation. And also the significance of the theoretical values by the presented theoretical equation is clarified.