• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6C
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• pp.259-265
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• 2012

This paper investigates engineering characteristics of lightweight soils mixed with air foam and tire powder. Lightweight soils could be used as foundation materials, back-fills of reducing vibrating or abutment, and so on. Unconfined and triaxial compression tests were carried out to analyze strength and deformation characteristics of lightweight soils by changing target moist unit weight and cement contents. In comparison with strength characteristics of two different kinds of lightweight soils with same most unit weights ($13kN/m^3$), unconfined compression tests showed similar compressive strength, however, triaxial compression tests showed that compressive strength of lightweight soils mixed with waste tire powder was relatively larger strength than that of lightweight soils mixed with air foam because of elasticity of waste tire powder. Also, unconfined and triaxial compressive strengths of most of lightweight soils increase with increases of moist unit weight and cement contents. However, the strength of lightweight soils mixed with air foam under $11kN/m^3$, when moist unit weight exceeds a certain cement contents, decreases even though cement contents increase because of the effect in a void gap of air foam.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.5
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• pp.1486-1494
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• 1991

본 연구에서는 분말단조 공정의 유한요소 컴퓨터 시뮬레이션을 위한 기초연구 로 다공질예비성형체의 기지(matrix)인 합금강의 변형률 속도와 온도에 따른 일축 압 축하의 열-점소성 거동을 조사하였다. 변형률 속도와 온도의 영향을 동시에 고려하 기 위하여 변형률 속도 .epsilon.=$10^{-4}$, $10^{-2}$ 및 $10^{-1S-1}$과 온도범위 800~ 1200.deg. C에 대하여 실험하였다.

• Journal of the Korean Geotechnical Society
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• v.36 no.2
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• pp.17-28
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• 2020

With respect to the tensile strength of volcanic rocks in Jeju Island, a comparative study was conducted using the existing research results and the test results performed in this study. In addition, the characteristics and effectiveness of the cohesion and internal friction angle estimated from the Brazilian tensile strength and unconfined compressive strength of Jeju volcanic rocks were investigated. As results, the Brazilian tensile strength of Jeju volcanic rocks was closely related to absorption, and decreased exponentially as the absorption increased. It was confirmed that the internal friction angle was closely related to the ratio of unconfined compressive strength to Brazilian tensile strength (σ_c / σ_t), and increased logarithmically as the ratio of σ_c / σ_t increased. In addition, the ratios of σ_c / σ_t of Jeju volcanic rocks were in the range of 5~20 depending on the magnitude of internal friction angle. In the case of cohesion, it was closely related to the absorption and Brazilian tensile strength. The cohesion exponentially decreased as the absorption increased, such as the relation between the Brazilian tensile strength and absorption. It was confirmed that there was a linear relation between the cohesion and Brazilian tensile strength.

• Journal of the Korean GEO-environmental Society
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• v.15 no.4
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• pp.61-67
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• 2014

With a view to resolving environmental problems of hazardous cement, this study seeks to identify the unconfined compressive strength and bending strength of the vegetation block designed herein by utilizing high-strength natural soil stabilizer instead of cement. Soil stabilizer is mainly made of mixture of short fiber extracted from natural fiber and lime, etc. Soil stabilizer reinforces the shearing strength of soil to improve block supportive power and durability while preventing flood and frost damages. For the unconfined compressive strength test, test pieces were prepared by mixing soil stabilizer and weathered soil in different ratios of 6 %, 12 % and 18 %. Experiments were carried out according to curing periods of 5th, 7th, 14th and 28th of the day. For bending strength test, blocks were made in the same mixture ratios as for the unconfined compressive test and tested for each stage. Also, to evaluate for the field applicability, proposed optimum water content considering the characteristics of the soil stabilizer. Permeability test result for the vegetation block, satisfied by the KS F 4419 quality standards.

• The Journal of Engineering Geology
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• v.18 no.2
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• pp.227-232
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• 2008

In this study, the pull out resistance characteristics of an anchor bar to support a spillway installed in a slope are investigated by field tests. The injection materials were a cement mortar and cement milk. Unconfined compression strengths of those materials under several conditions were measured. As the result of compression test, the unconfined compression strengths of the cement mortar and the cement milk have positive proportional relation-ship with the water-cement ratio. They also have negative proportional relationship with increasing the curing time. In the same condition of water-cement ratio and curing time, the unconfined compression strength of cement milk is larger than that of cement mortar. In order to reduce the eccentricity in anchor bar during pull-out test in the field, the installation apparatus was improved by inserting a nut type of steel fixing coupling into the anchor bar. As the result of the pull-out test, the strength modification of cement milk was increased steeply at the early curing time. However, that of cement mortar was increased gradually with passing the curing time. Therefore, the cement milk has to use as the injection material for a prompt construction of anchor bar because the strength modification of cement milk is occurred at the early curing time.

• Journal of the Korean Geotechnical Society
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• v.37 no.11
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• pp.23-36
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• 2021

In this paper, the effect of shear rate on internal friction angle and unconfined compressive strength of non-cemented and cemented sand was investigated. A dry Jumunjin sand was prepared at loose, medium, and dense conditions with a relative density of 40, 60 and 80%. Then, series of direct shear tests were conducted at shear rates of 0.32, 0.64, and 2.54 mm/min. In addition, a cemented sand with cement ratio of 8% and 12% was compacted into a cylindrical specimen with 50 mm in diameter and 100 mm in height. Unconfined compression tests on the cemented sand were performed with various shear rates such as 0.1, 0.5, 1, 5 and 10%/min. Regardless of a degree of cementation, the unconfined compressive strength of the cemented sand and the angle of internal friction of the non-cemented sand tended to increase as the shear rate increased. For the non-cemented sand, the angle of internal friction increased by 4° at maximum as the shear rate increased. The unconfined compressive strength of the cemented sand also increased as the shear rate increased. However, its increasing pattern declined after the standard shear rate (1 mm/min). A discrete element method was also used to analyze the crack initiation and its development for the cemented sand with shear rate. Numerical results of unconfined compressive strength and failure pattern were similar to the experimental results.

• Journal of the Korean Geotechnical Society
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• v.17 no.1
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• pp.5-13
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• 2001

강도 또는 변형 이방성은 층리진 최적암, 박층모양의 변성암, 균일하게 절 리가 나있는 암석에서 흔히 볼 수 있다(Amadei, 1982, 1996). 특히, 대구지역은 퇴적암의 일종인 셰일로 구성되어 층리면의 각도에 따라 역학적인 특성이 달리 산정되어져야 한다. 이에 본 연구에서는 층리면의 각도를 달리하여 시료를 성형한 후 각종 시험을 수행하였다. 그 결과 일축 압축강도는 수평면과 층리면이 이루는 각이 0$^{\circ}$, 90$^{\circ}$에서 최고 강도를, 60$^{\circ}$에서 최저 강도를 나타내었다. 또한 간접 인장시험과 점 하중시험, 탄성파시험에서는 90$^{\circ}$에서 최고값을, 0$^{\circ}$에서 최저값을 보였다. 그리고, 층리에 따른 퇴적압의 일축 압축강도를 간접 인장강도, 점하중강도와의 상관성을 분석하여 각각의 관계를 회귀분석을 통한 상관식으로 나타내었다. 추가적으로 층리에 따른 공학적특성을 정량적으로 나타내었다.

• The Journal of Engineering Geology
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• v.2 no.1
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• pp.36-46
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• 1992

Granite core samples and bulk samples were first subjected to petrographic examination to determine weathering degrees. Secondly, their physical or mechanical properties including specific gravity, porosity, sonic wave velocity and uniaxial compressive strength were measured. The results were correlated to investigate the influences between properties including physical and mechanical properties, weathering degrees, and rock textures. Porosity and P wave velocity were found the most useful indices in determining the weathering degrees of granites.

• Tunnel and Underground Space
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• v.19 no.5
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• pp.450-462
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• 2009

To analyze the behavioral characteristics of rocks on indirect tests and uniaxial compressive strength, researchers have investigated 1417 pieces of rock block, which include igneous, metamorphic and sedimentary rocks in Korea. The same behavioral characteristics have been shown in every type of sedimentary rock and in the same species of rock in the case of Brazilian strength application. This suggests that correlations of rocks for geological considerations can lead to high reliability of the experimental results in case of an indirect method.

• Proceedings of the KSEG Conference
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• 2002.04a
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• pp.211-218
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• 2002

TBM 터널굴진시 공법적합성을 평가하기 위한 현장조사 및 물리탐사와 세부지질조사를 수행하였다. 해당지역은 부산시 진구 가야동과 동구 수정동이며 인근 수원지인 덕정정수장에서 생산하는 수돗물을 수정산 배수지까지 확대 공급함으로서 송수공급 계통의 이원화로 안정적인 수돗물공급을 수행하기 위한 배수지터널이다. 이론적으로 굴착속도는 암반의 반발경도, 일축압축강도, 석영함량 및 각종 지질특성에 의하여 좌우되는데, 실지 시공에 있어서는 현장여건상 지질조건이나 일축압축강도등 한정된 자료들을 토대로 시공에 임할 수밖에 없다. 이러한 한계를 극복하기 위한 모형개발을 목표로 본 연구에서는 다양한 현장시험을 토대로 한 TBM 굴진 적합성을 검토하고자 하였다. 국내 시공경험상 및 지질특성만을 고려 할 때 본 과업구간의 TBM 적용성은 양호할 것으로 판단하였으나, 뚜렷한 근거에 의거하지 않은 설계는 시공단계에서 엄청난 손실을 야기하게 되므로 보다 상세한 검토를 수행하게 되었다. 본 연구에서는 TBM 공법선정의 적합성을 검토하기 각종 조사 자료들을 정리하였고, 국내시험의 한계점들을 극복하기 위한 적합한 모형개발의 필요성을 제시하고자 하였다.