• Journal of the Korean Geotechnical Society
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• v.23 no.4
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• pp.91-100
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• 2007

In most design codes, soils are classified as either sand or clay, and appropriate design equations are used to represent their behavior. For example, the behavior of sandy soils is expressed in terms of the relative density, whereas consistency limits are often used for clays. However, sand-clay mixtures, which are typically referred to as intermediate soils, cannot be easily categorized as either sand or clay and therefore a unified interpretation of how the soil will behave at the transition point, i.e., from sandy behavior when fines are low to clay behavior for high fines content, is necessary. In this study, active natural clays are mixed with sand, and the fines content varied in order to produce different structures, ranging from one state where only sand particles form the soil structure to another where the matrix of fines make-up the structure. While paying attention to the granular void ratio in order to clarify the shear properties of sand-clay mixtures with increasing fines content monotonic, shear tests were performed on isotropically, and anisotropically consolidated specimens. From the test results, it was observed that the monotonic shear strength of sand-clay mixtures is dependent on the granular void ratio.

• Korean Journal of Agricultural Science
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• v.10 no.2
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• pp.277-291
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• 1983

In order to investigate the shear characteristics of earth structure after construction. Four sample soils with different gradation were selected and compacted under the optimum moisture content and the maximum dry density. And the direct shear test and the triaxial compression test were performed with those sample soils under various pre-compression loads. The results were summarized as follows; 1. With the increase of the percent passing of No. 200 sieve, the cohesion of soil increased regularly and the internal friction angle of soil decreased with slow ratio. 2. The pre-compression increased the shear strength of compacted cohesive soil. The increase of cohesion was very apparent but the internal friction angle didn't show such regular tendency. 3. With the increase of pre-compression load, the slope of stress-strain curve showed steep at the early stage of horizontal strain. The vertical strain was small at the compression stage and big at the expansion stage. 4. When the vertical stress of shear test with increase in the horizontal strain was small, stress ratio(shear stress vs. vertical stress) of sample showed the largest value and the slope of stress ratio curve showed also steep. 5. When the sample was had the same condition, the cohesion of soil showed bigger value in the triaxial compression test and the internal friction angle of soil showed bigger value in the direct shear test.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.717-726
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• 2005

Shear test data have been extracted from previous experimental research and compiled into a database that may be the largest ever made. In this paper, the shear database (SDB) was used for evaluating shear design provisions for both reinforced concrete (RC) beams and prestressd concrete (PSC) beams. A discussion on the use of the results of this evaluation related to calibration and strength reduction factor for the shear design provisions was also provided. It was observed that the shear design provisions did not provide good predictions for RC members and gave very poor predictions especially for RC members without shear reinforcement. On the other hand, the limit on shear strength contributed by transverse reinforcement was observed to be lower than necessary. The shear design provisions gave very unconservative results for the large RC members (d>700mm) without shear reinforcement having light amount of longitudinal reinforcement $(\rho_w<1.0\%)$. However, for PSC members the shear design provisions gave a good estimation of ultimate shear strength with a reasonable margin of safety. Despite of a large difference of accuracy in prediction of shear strength for RC members and PSC members, the shear design provisions used a same shear strength reduction factor for these members. As a result, the shear design provisions did not provide a uniform factor of safety against shear failure for different types of members.

• The Korean Journal of Rheology
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• v.6 no.2
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• pp.157-164
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• 1994

인체 동맥혈관내 혈액의 유동현상을 수치적으로 해석하기 위해서는 혈액의 유변학 적 성질을 구성방정식으로 나타내어야한다. 본 연구에서는 혈액의 점성계수를 표현하기 위 하여 비뉴턴유체의 점성을 나타내는 식으로서 Carreau 모델, 수정 Cross 모델, 수정 Powell-Eyring 모델과 수정멱법칙모델을 사용하였고 원형관내 혈액의 정상유동을 수치모사 하기 위하여 겉보기점성계수를 이용하는 구성방정식을 운동량방정식에 적용하였다. Carreau 모델과 수정멱법칙모델을 적용할 때 레이놀즈수의 변화가 중심선상의 속도와 길이방향의 압 력변화에 미치는 영향을 고찰하였다. 전단율이 높은영역에서 혈액의 겉보기점성계수를 효과 적으로 나타낼수 있는 수정멱법칙모델을 제시하였다.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.3
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• pp.29-35
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• 2000

The present numerical study investigates heat transfer enhancement mechanism for suspensions of polystyrene particles in water. Numerical simulations were done for turbulent hydrodynamic fully developed flows in a circular duct with constant wall heat flux. The experimental result of microparticle suspensions show 25∼45% heat transfer enhancement over those of water. The present numerical results show the main parameter for the heat transfer enhancement of microparticle suspension in a circular duct is the change of velocity profile by the non-Newtonian fluid behavior.

• Geotechnical Engineering
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• v.4 no.2
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• pp.45-55
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• 1988

Chemical grouting is one of the ground.improvement methods for the purpose of cutting o($\boxUl$ water and increasing the strength of soil. It has ben reported that the effect of strength increasement of groued roils is due to increase of cohesion. In this study, the effect of cohesion on the shearing resistance of grouted soil 9.as intr.estigated tall.ouch triaxial compression test. According to the result of this research, It is found that the improved cohesion increases rapidly up to the maximum value at a small strain and subsequent decrease of cohericn is due to the breaking of grout chemical at a larger strain.

• International Journal of Highway Engineering
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• v.10 no.3
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• pp.1-10
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• 2008

Conventional RC/TS(resonant column and torsional shear) device usesa specimen with an aspect ratio(height-to-diameter) of 2:1 and this generates a maximum shear strain in the sample of about 1.5% at the maximum rotation of the drives system. The objective of this study is to modify RC/TS device to generate higher strain amplitude. The modifications include a new base pedestal to overcome the limitations in the travel of the drive system and modification of coil wiring to increase torque. The effects of the new coil wire on torque in the electro magnetic drive system were evaluated and the application of modified device was illustrated using sand soil.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.7-14
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• 2003

In this study, undrained shear test was performed$K_o$ consolidation in order to study the shear strength characteristics of oysters-marine clay mixtures for three mixed ratios(0%, 25% and 50%). And, in order to study shear strength characteristics of oysters-marine clay mixtures, three different effective vertical stresses(200, 300 and 400kPa) were applied for the $K_o$ consolidation tests. In addition three different axial strain rates(0.005%/min, 0.05%/min, 0.5%/min) were applied for the case of effective vertical stress, 300kPa. According to experimental results, the more mixed ratios were increased, the more deviator stress was increased by crushing effect of oysters particles. especially, when effective vertical stress is 300kPa and mixed ratio increase from 25% to 50%, Test shows the increase of shear strength. But axial strain rate was not effect on the undrained shear strength. In the comparison and analysis that are based on the values of tests on the oysters-marine clay mixtures and the Mayne & Bishop's empiric formula, the undrained shear strength ratio shows a similar pattern of the tests. But for the prediction of the coefficient of the pore water pressure, the value of empiric formula shows more overestimated than the values of the tests at 0%, mixture ratio.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.2
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• pp.109-117
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• 1983

Dynamic shear modulus of the compacted clayey soil was determined by the resonant column test to study the parametric effects of confining pressure, shear strain amplitude, molding water content, compaction energy, void ratio and the degree of saturation. The effect of each of these parameters on the dynamic shear modulus found to be significant and can be explained in terms of the changes in soil by compaction. Dynamic shear modulus of the compacted soil is increased significantly by compaction and compaction at the dry side of the optimum moisture content is much more effective. It is also found that the dynamic shear modulus showes a good correlation to the static shear strength of the compacted soil. Therefore the dynamic shear modulus of the compacted soil for a certain confining pressure may be obtained ea8i1y from the unconfined compression strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.95-102
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• 2021

Elastometic bearings using flexible rubber materials have recently been widely applied for seismic retrofit of bridges. However, due to various factors, the aging of the rubber material progresses, which causes the shear stiffness change of the bearing, which affects the seismic performance of the bridge. For natural rubber, accelerated heat aging test was performed with variables of heating temperatures and exposure time to analyze shear characteristics. As aging progresses (i.e. increase of temperature and exposure time), the maximum shear stress and shear strain decrease. Also, the shear stiffness is greatly increased at the same shear strain. This means that the rubber material is hardened, implying that the seismic performance of the elastomeric bearing becomes poor.