• Journal of the Korean Geotechnical Society
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• v.27 no.9
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• pp.67-76
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• 2011

Bearing capacity of pile foundations in cold region is dominated by adfreeze bond strength between surrounding soil and pile perimeter. Adfreeze bond strength is considered to be the most important design parameter for foundations in cold region. Many studies in last 50 years have been conducted to analyze characteristics of adfreeze bond strength. However, most studies have been performed under constant temperature and normal stress conditions in order to analyze affecting factors like soil type, pile material, loading speed, etc. In this study, both freezing temperature and normal stress acting on pile surface were considered to be primary factors affecting adfreeze bond strength, while other factors such as soil type, pile material and loading speed were predefined. Direct shear box was used to measure adfreeze bond strength between Joomoonjin sand and aluminium because it is easy to work for various roughness. Test was performed with temperatures of > $0^{\circ}C$, $-1^{\circ}C$, $-2^{\circ}C$, $-5^{\circ}C$, and $-10^{\circ}C$ and vertical confining pressures of 1atm, 2atm, and 3atm. Based on the test results, the effects of temperature and vertical stress on adfreeze bond strength were analyzed. The test results showed that adfreeze bond strength increases with decreased temperature and increased vertical stress. It was also noted that two types of distinct sections exist, owing to the rate of increase of adfreeze bond strength along the change of freezing temperature: 1)rapidly increasing section and 2)gradually decreasing section. In addition, the results showed that a main factor affecting adfreeze bond strength switches from friction angle to adhesion as freezing temperature decreases.

• Geotechnical Engineering
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• v.10 no.2
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• pp.121-140
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• 1994

This paper presents the probabilistic model to evaluate the three-dimensional stability of layered deposits and c-0 soil slopes. Rotational slides are assumed with a cylindroid control part terminated with plane ends. And the potential failure surfaces in this study are assumed with the logarithmic spiral curve refracted at boundary of layers. This model takes into consideration the spatial variabilities of soil properties and the uncertainties stemming from insufficient number of samples and the discrepancies between laboratory measured and in -situ values of shear strength parameters. From the probabilistic approxi mate method (FOSM and SOSM method), the mean and variance of safety factor are calculated, respectively. And the programs based on above models is developed and a case study is analysed in detail to study the sensitivity of results to variations in different parameters by using the programs developed in this study. On the basis of thin study the following conclusions could be stated : (1) The sensitivity analysis shown that the probability of failure is more sensitive to the uncertainty of the angle of internal friction than that of the cohesion, (2) The total 3-D proability of failure and the critical width of failure are significantly affected by total width of slope. It is found that the total 3-D probability of failure and the critical width of failure increase with increasing the slope width when seismic forces do not exist and the total 3-D probability of failure increases with increasing the slope width and the critical width of failure decreases when seismic intensity is relatively large, (3) A decrease in the safety factor (due to effect such as a rise in the mean ground water level, lower shear strength parameters, lower values for the correction factors, etc.) would result in reduction in the critical width of failure.

• Korean Journal of Agricultural Science
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• v.12 no.1
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• pp.86-100
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• 1985

In order to investigate the strength characteristics of weathered granite soils in unsaturated state, the five physically different weathered granite soils and the common soil (sandy loam) were examined. The disturbed and the undisturbed material were prepared for triaxial compression test. The following conclusions were drawn from the study; 1. Dry density of the undisturbed soil samples was lower than maximum dry density determined from the compaction test and it showed the higher value at the well graded soil. 2. The failure strength of the samples decreased with the increase of moisture content of the soil and these results were highly pronounced at the common soil sample having a good cohesive property. 3. On weathered granite soils, the cohesion was lower measured and the internal friction angle highly, the decrease rate at internal friction angle with increase of moisture content of the soil was more significant than that of cohesion 4. The modulus of deformation of the samples decreased with increase of moisture content of the soil and these phenomena were highly pronounced at the weathered granite soils than common soil. 5. The failure strength of the samples increased with in crease of confining pressure and effect of confining pressure on failure strength was highly significant at the lower moisture content of the soil.

• Elastomers and Composites
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• v.48 no.3
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• pp.225-231
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• 2013

In this study, we observed the effect of carboxylated SBR latex and zinc oxide on styrene-butadiene-styrene( SBS) composites for improving abrasion and debris. SBS composite, which added only silica, showed poor mechanical properties, NBS abrasion, and debris, caused by strong filler-filler interaction of silica. In case of adding carboxylated SBR latex, mechanical properties, NBS abrasion and debris of SBS composite were improved. Because of carboxyl group of carboxylated SBR latex interacted with silanol group of silica. Both carboxylated SBR latex and zinc oxide were added, SBS composite showed highest mechanical properties, NBS abrasion, and debris by forming ion cluster between carboxylated SBR latex and zinc oxide. By FT-IR analysis, ion clusters were confirmed that observed zinc carboxylated group stretch peak at $1550{\sim}1650cm^{-1}$ range. SBS composite, SC-4, showed excellent mechanical properties ; tensile strength $156kgf/cm^2$, elongation 936%, tear strength 59.4kgf/cm ; and excellent abrasion characteristics ; NBS abrasion 338%. Also, debris of SC-4 was minimized and showed wave-shape in fracture surface.

• Journal of the Korean GEO-environmental Society
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• v.11 no.7
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• pp.33-43
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• 2010

The physical characteristics of the marine clay in the Korean Peninsula, specifically Pusan areas of the south coast of Korea, were previously studied and reliable data from harbor construction projects were used for the relationship analysis of geotechnical strength parameters. The sample of marine clay classified to ML, MH, CL, CH and ML-CL from USCS were included for the analysis while the samples classified to SC were excluded in order to raise the degree of data analysis. Geotechnical strength properties, such as undrained shear strength, sensitivity ratio, and effective friction angle were analyzed and evaluated using the data obtained from unconfined compression test, triaxial compression test and field vane test. Abnormal values were extracted through statistical analysis. Moreover, the reliability of the results was improved by performing the evaluation of disturbance. Linear regression analysis was used for the relationship analysis, between undrained shear strength and depth. The relationship equation between undrained shear strength and depth was derived from the analysis of unconfined and triaxial compression test data of samples obtained at same location. Consequently, The relationship between depth and undrained shear strength is $S_u=0.015148D+0.04624$ and the undrained shear strength derived from the triaxial compression test was estimated to be about 1.26 of derived from the unconfined compression test.

• The Journal of Engineering Geology
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• v.11 no.1
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• pp.1-11
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• 2001

The geological characteristics of Korea are that we can encounter the rock layer only after 10m of excavation, methods to presume the rock pressure distribution of the rock layer is urgently needed. When using the existing empiric science of Terzaghi-Peck, Tschebotarioff to measure the rock pressure of the rock layer, underestimate the real strength because of the cohesion is ignored. Therefore calculating the horizontal sliding force of wedge block, which includes the dips and shear strength of discontinuities and surcharge load etc., think to be to getting a closer rock stress of the real rock pressure acting upon the earth structure in rock mass. This research use Coulomb soil pressure theory assuming that the backfill soil will yield wedge failure when it has cohesion, applying Prakash-Saran(l963), and then it uses equilibrium of force and shear strength $\tau$=c+$\sigma$tan $\Phi$ of the cliscontinuities. Analyzing shear strength and dips of cliscontinuities using calculated theory according to the status of discontinuities aperture, we were able to find out that because the cohesion and friction angle of the rock layer itself is large enough, how the dip directions and dips facing the excavation face is the only factor deciding whether or not the rock stress is applied. The evaluated theory of this research should be strictly estimated, so that the many parameters such as c, $\Phi$value, types and structures of rock class, excessive lateral pressure, dynamic load, earthquake, needed later when calculating shear strength of discontinuities and especially the ground water effect acting on rock layer should be coumpted with many measuring data achieve at the insite to study the application.

• Journal of the Korean Geotechnical Society
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• v.33 no.12
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• pp.7-20
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• 2017

In this study, effects of grain size distribution on the shear strength and rheological properties are investigated for coarse- and fine-grained soils by using direct shear apparatus. Shear strengths are estimated for fine-grained soils with the maximum particle size of 0.075 mm and coarse-grained soils with the maximum particle size of 0.425 mm and fine contents of 17% prepared at dry and liquid limit states. The direct shear tests are conducted under the relatively slow shear velocity, which corresponds to the reactivated landslide or debris flow after collapse according to the landslide classification. In addition, for the evaluation of rheological properties, residual shear strengths for both fine- and coarsegrained soils prepared under liquid limit states are obtained by multiple reversal shear tests under three shear velocities. From the relationship between residual shear strengths and shear rates, Bingham plastic viscosity and yield stress are estimated. The direct shear tests show that cohesions of fine-grained soil are greater than those of coarse-grained soil at both dry and liquid limit states. However, internal friction angles of fine-grained soil are smaller than those of coarse-grained soil. In case of rheological parameters, the plastic viscosity and yield stress of fine-grained soils are greater than those of coarse-grained soils. This study may be effectively used for the prediction of the reactivated landslide or debris flow after collapse.

• Journal of the Korean Geosynthetics Society
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• v.11 no.4
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• pp.17-25
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• 2012

In this study, it was carried out reliability analysis and slope stability analysis in a standard cross-sectional embankment on high speed railway. It was confirmed that changing tendency of safety factor with various parameter of each soil materials properties and trends of the probability of failure according to the reliability index. The results have shown that a safety factor were relatively large affected an cohesions and internal friction angle of soil compared to the unit weight of soil. Also, most of the standard cross-sectional embankment in high speed railway was generally evaluated the level of below average (below average) by the reliability analysis according to criterion in US. Army but the 12m height of dry embankment case was shown bad condition as Poor.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.395-399
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• 2009

현재 계획 또는 설계단계에서 수행되고 있는 우수 관거 시스템의 수리계산에서는 연결관의 마찰손실만을 감안하여 수행하고 있으며, 맨홀에서의 수두손실은 고려되지 않는 실정이다. 특히 과부하 $90^{\circ}$ 접합맨홀 내부에서의 복잡한 흐름 현상에 의하여 발생하는 에너지 손실은 일반적인 직선 연결 맨홀에 의해서 발생하는 에너지 손실과 큰 차이를 보이지만 현재 우수 관거 설계 및 관리에서는 이를 대부분 고려하지 않는 실정이다. 또한 직선으로 연결된 맨홀보다 $90^{\circ}$ 접합 맨홀은 유수교란에 의한 에너지 손실이 커지므로 이에 대한 $90^{\circ}$ 접합 맨홀에서의 에너지 손실 저감에 대한 연구가 필요하다. 그러므로 본 연구에서는 합류 맨홀 중 $90^{\circ}$ 접합 맨홀에서의 에너지 손실 저감 방법의 분석을 위하여 하수도시설기준(환경부, 2005)의 표준 1호(원형), 특 1호(사각형) 맨홀을 각각 축소 제작하고, 수리실험 장치를 제작하여 수리 실험을 실시하였으며, 실험결과를 benching을 사용하지 않은 $90^{\circ}$ 접합 맨홀의 평균 손실계수를 산정한 윤세의 등(2008)의 실험 결과와 비교하였다. 접합위치를 변경한 원형 맨홀 CASE B에서의 평균 손실계수는 1.1로 산정되어 CASE A의 1.6보다 크게 감소하였다. 접합위치를 변경한 사각형 맨홀 CASE B에서는 1.5로 산정되어 손실계수의 감소폭이 적었으나, 접합위치를 변경하고 side benching을 설치한 CASE C에서의 평균 손실계수는 1.1로 산정되어 CASE A의 사각형 맨홀의 손실계수 1.6에 비하여 큰 감소 효과를 나타내었다. 따라서 $90^{\circ}$ 접합 원형 맨홀에서는 접합 위치를 변경시킨 CASE B의 형태를 사용하고, 사각형 맨홀에서는 접합 위치를 변경시키고 side benching을 설치한 CASE C의 형태를 사용하면 우수 관거 시설의 배수능력을 향상 시킬 수 있을 것으로 판단된다.

• Journal of the Korean GEO-environmental Society
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• v.3 no.1
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• pp.5-12
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• 2002

The effects of ground water level, shear strength parameters of refuse, and geological condition of ground on the slope stability of uncontrolled waste landfill were studied. The Janbu method of slices based on the limit equilibrium method was used to calculate the minimum factor of safety with respect to slope stability of landfill. The analytical results showed that the factor of safety for a fully dried condition of landfill increased 2.4~2.8 times as great as that for a fully saturated condition of landfill. Under the condition of actual ground water level, the factor of safety linearly increased with increasing both cohesion and internal friction angle of refuse. Also, when the potential failure surface passed through the underlying layer, the factor of safety and shape of potential failure surface were found to depend on geological conditions of underlying layer.