• Geotechnical Engineering
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• v.7 no.1
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• pp.7-14
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• 1991

Determination of dynamic shear modulus of soil was made by measuring directly the velocity of ultrasonic shear waves transmitted through the specimen. The PUNDIT, a generator and detector of ultrasonic waves, has been used to measure the propagation velocity. Forty -six tests of compacted soil at seven different void ratios and seven varying degrees of saturation with four types of materials were made in this study. The primary importance in this study was the investigation of the relations among the para meters which influenced G-modulus, As a results of analysis, the dynamic shear modulus of soil tends to decrease with an increase of void ratio, and also it is affected by soil types. In case of using PUNDIT, the proper range of the specimen length is from 5cm to 8cm. And the degree of saturation doesn't affect the dyn- amic shear modulus of soil.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.2
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• pp.65-76
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• 1991

A numerical solution method for the evaluation of the static and dynamic horizontal active thrusts exerted by a backfill, consisting of two or three layers of different properties, on a retaining wall is proposed in the present study based on the Mononobe-Okabe analysis. Using the proposed method, the efficient type in forming a backfill with two layers of different properties is analyzed. In addition, for the design examples of a backfill made up of two or three layers of different properties, the static and dynamic horizontal active thrusts computed using the soil property of each layer are compared with those obtained from the proposed method, and also the problems expected in design are presented based on the comparisons.

• Journal of the Korean Geosynthetics Society
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• v.2 no.1
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• pp.27-37
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• 2003

The factors affecting shear strength and friction characteristics of the fiber-mixed soil can be classified into engineering properties of soil; particle-size, distribution, and particle shape, physical and mechanical properties of fiber; shape, length, diameter, tensile strength, elastic modulus, friction coefficient, and mixed ratio and external factors; confined stress and compaction condition. In this study, a series of shear friction tests and pull-out tests were performed to evaluate the friction properties of fiber-mixed soil according to soil type, fiber type, fiber mixed ratio and compaction degree. The materials and test conditions used in this study are as follows. Soils: SM and ML; mixing fibers: three types of polypropylene fibers(net type 38mm and 60mm, and line type 60mm); reinforcement: geogrid; mixing ratio: 0.2% and 0.3%; degree of compaction : 85% and 95%.

• Geotechnical Engineering
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• v.28 no.1
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• pp.39-44
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• 2011

TDR 함수량계는 전자기파를 이용하여 흙의 밀도와 함수비를 비파괴적으로 신속하게 평가하는 유망한 기술이다. TDR 시험법은 10~20cm 길이의 2~3개의 탐침을 지중에 관입시킨 후 전자기파의 이동시간을 측정하여 유전상수($K_a$)를 산정한다. 제안식을 이용하여 유전상수로부터 체적함수비(${\theta}$)의 산정이 가능하므로, 이 시험법은 흙의 함수비를 측정할 수 있는 비파괴시험 장치로 개발되어 활용되고 있다. 또한, 흙의 종류에 따른 보정상수가 파악되어 있는 경우에는 현장 밀도와 현장 함수비를 동시에 평가할 수 있으므로, TDR 함수량계를 이용하여 성토지만비나 노상토에 대한 신속하고 간편한 다짐관리가 기능하다.

• Journal of the Korean Geotechnical Society
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• v.25 no.5
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• pp.47-52
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• 2009

A sand replacement method is commonly used to determine the density of the compacted soils. The density of the test or compacted soil is computed on the assumption that the calibration container has approximately the same size or volume and allows the sand to deposit approximately in the same way as a test hole in the field. The sand filling process is simulated in the laboratory and its effect on the determination of density is investigated. Artificially-made holes with different heights and bottom shapes are prepared to simulate various shapes of the test hole in the field. Three sands with different gradations are used in the testing to examine how sand grain size influences the determination of density in the field. As the height of a test hole increases, the error between known density and calculated density decreases, regardless of the types of test hole and sand used. The results of this study can be used to reevaluate and revise the test method for soil density by the sand replacement method.

• Geotechnical Engineering
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• v.14 no.2
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• pp.79-92
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• 1998

Parametric studies based on laboratory pilot tests were performed to investigate the relationships between electrical resistivity and properties of contaminated soils. Three kinds of sandy soils sampled and leachate from an industrial waste landfill were mired to model the contaminated soils. Electrical resistivity of soils was measured by using a simulated resistivity cone penetrometer probe. In the experiments. the electrical resistivity was observed by changing the water content, void ratio, unit weight, degree of saturation, and concentration of the leachate. The test results show that the electrical resistivity of soils depends largely on the water content and the electrical property of pore water rather than unit weight and types of soils.

• Geotechnical Engineering
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• v.14 no.4
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• pp.163-176
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• 1998

To apply piezocone test to soil classification, several classification charts based on correlations between its results and basic characteristics of soils have been developed. However, it is necessary to investigate their applicability to Korean soil, since they were the results obtained from the limited number of foreign sites. In this study, 41 piezocone penetration bests for various sixtes spreading widely over Korean territory were carried out. Correlations between piezocone teat results and basic characteristics and the applicability of existing classification charts were investigated. Conclusively, new classification charts based, on Unified Soil Classification System were developed with a local confidence.

• Journal of the Korean Geosynthetics Society
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• v.5 no.3
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• pp.25-30
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• 2006

Large-scale direct shear tests were conducted in order to evaluate both the shear strength of soil itself and the interface shear strength between soil and woven geotextile. Two types of soil (sand and clay) with a woven geotextile were used in the experimental program. Total nine tests were conducted in this study. It has been found from the experimental results that the friction angle of sand itself were $30^{\circ}$. Interface friction angle between woven geotextile and sand showed $26^{\circ}$ indicating an efficiency of 87%. Similarly, interface friction angle between woven geotextile and clay showed $7.7^{\circ}$.

• Journal of the Korean Geotechnical Society
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• v.17 no.1
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• pp.119-129
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• 2001

연약지반 개량을 위한 시멘트의 사용은 깊은 심도의 점토 지반을 개량하는데 일반적으로 사용되는 기술이 되었다. 시멘트는 지반의 강도를 증가시키고 압축성을 감소시키는 역할을 한다. 시멘트-흙 혼합물의 강도 증가에는 여러 가지 요소가 있는데 이중 대표적인 것은 시멘트량, 흙의 종류, 함수비, 양생시간 등을 들 수 있다. 시멘트 첨가량이 적은 경우, 전단 강도증가는 기본적으로 시멘테이션 효과로 인한 점착력의 증가에 의한 입자들간의 마찰력으로부터 발생한다. 이러한 거동은 과압밀된 흙의 거동과 유사함을 볼 수 있다. 시멘트량이 많은 경우, 강도 증가의 주원인은 입자간의 물리적 결합에 기인하는데 이는 연약한 암석과 비슷한 거동을 한다. 시멘트 고화처리 흙의 응력-변형 거동을 분석하기 위해 한계상태 이론을 적용하였다. 그리고, 토립자간의 시멘테이션 효과를 반영하기 위해 새로운 한계상태 파라메타를 도입하였으며 시멘트 고화처리 점토의 거동을 분석하기 위한 새로운 한계상태 모델을 제시하였다.

• Geotechnical Engineering
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• v.11 no.4
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• pp.87-98
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• 1995

Laboratory tests were performed on modeling of in situ remediation of contaminated soils by aqueous solution extraction, thus investigating the feasibility of in situ treatments of soil to promote desorption of organic hazardous wastes. The investigation was conducted using phenol, aniline, quinoline, and 2-napthol adsorbed onto a UH40 soil, and various aqueous solutions were used to desorb, or otherwise remove, these organic contaminants. Decontaminants consisted of deionized water as a reference, hydrogen peroxide, acidy, bases, and surfactants. In situ conditions were modeled in the laboratory by permeating potential extracting liquids through reconstituted, contaminated soil specimens under controlled hydraulic gradients and stress condition through flexible wall permeameter tests. Sodium hydroxide desorbed phenol effectively. Aniline was effectively descorbed by nonionic surfactant. Anionic surfactant remediated quinoline and 2-napthol.