• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.3 no.2
• /
• pp.45-59
• /
• 1983

This study aims at investigating the deformation and strength characteristics on reconsolidated-remoleded saturated clay sampled at the downstream of Young-san river, in Cheollanamdo through a series of both drained and underained triaxial tests by means of the critical state concept. Among several constitutive equations developed so far, the Cam-clay model, the modified Cam-clay model and the dilatancy model are used. The prediction of strains is obtained and the value of prediction is compared with that of observation. For the clay specimen, the prediction of volumetric strain on the dilatancy model is well consistent with the observation and the prediction of shear strain on the modified Cam-clay model coincides exactly with the observation.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.5
• /
• pp.89-98
• /
• 2008

In this study, the behaviour of an unsaturated soil was analyzed by performing $K_0$ consolidated triaxial tests. Unsaturated triaxial tests were performed with matric suctions for weathered soils and stress paths under consolidation and stress-strain relationships under shear were obtained. As a result, the $K_0$ value decreased as the matric suction increased. Besides, both isotropic and $K_0$ conditions had similar shear strength envelopes at the same matric suction. Especially, strength parameters could be obtained by stress variables used in the critical state theory more reasonably than by those of Mohr circles at failure.

• Geotechnical Engineering
• /
• v.5 no.4
• /
• pp.37-46
• /
• 1989

The object of this paper is to study the general characteristics of overconsolidated silty clays subjected to repeated loading. The samples are first remolded. overconsolidated and a series of strain - controlled triaxial repeated tests are carried out. Generally the relationship of deviator stress - axial strain of overconsolidated clay is similar in pattern to the normally consolidated clay under single load. But the behavior of the pore water pressure build up in the sample subjected to repeated loading is dependent upon the consolidation history and the level of repeated stress. Therefore through the series of the tests, the characteristics of stress -strain relationship of soils which are differentlly overconsolidated are investigated, analysed and then compared with each soils. And also, from the relationship of test results, the strength and strain characteristics of soils are obierved. The equilibrium lines which presents the critical repeated stress and equilibrium state in the sample under repeated loading, are often straight, but may be curved. And the tendency of the equilibrium lines is observed as to the variation of overconsolidation ratio.

• Journal of the Korean Geotechnical Society
• /
• v.20 no.9
• /
• pp.105-114
• /
• 2004

Consolidation characteristics have been investigated by using Rowe cell consolidation tester for dredged soil, which is more than two times as much as the liquid limit. To examine the effects of variation of water content on consolidation characteristic, tests were carried out varying the initial water content from $100\%\;to\;150\%.$ The results were compared with the consolidation characteristics of remolded clay. The test results showed that the hither the initial water content of dredged clay was, the more noticeable the non-linear behavior of e-log P curves occurred. The variation of the gradient was apparent to load stage 40kPa and became less apparent after load stage 80kPa on the e-log P curves. Ratio of compression index stayed within the range suggested by Mesri and variation of initial water content has hardly influenced the coefficient of consolidation. On the contrary, it was found that the magnitude of consolidation load affects the vertical coefficient of consolidation. The variation of stratum thickness during consolidation processing needs to be taken into consideration since hydraulic fill would go through a much larger scale strain than land soil when it is subject to a load. In this study, the consolidation period considering the variation of stratum thickness was analyzed and the results were compared with those of existing consolidation studies which did not consider the variation of stratum thickness. According to the results of the study, the consolidation period of the ground with a larger strain was calculated more close to observed value in case of Mikasa theory which takes the variation of stratum thickness into consideration.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.29 no.6
• /
• pp.257-263
• /
• 2019

Lightweight geopolymers were fabricated with non-milled IGCC slag and Si sludge as a bloating material. The relationship between addition amount of Si sludge and physical/chemical properties of lightweight geopolymers was investigated. When the geopolymers were made by mixing IGCC slag, alkali activator, and more than 10 wt.% Si sludge, the temperature of the geopolymer pastes reached higher than 130℃ in a few minutes. This exothermic reaction accelerated the geopolymer reaction; however, it was difficult to make geopolymer specimens because of a rapid bloating reaction. Both compressive strength and density of the specimens tend to decrease with an addition of Si sludge; however, there was little difference in both compressive strength and density with addition of Si sludge more than 10 wt.%. Because there was a limit to get low density geopolymers by simply increasing the addition of Si sludge, the control of pore size and distribution of geopolymer is more important by controlling flow rate of the paste through the control of W/S ratio. Therefore, it is important to control process conditions, appropriate W/S ratio for the bloating than the control of Si sludge. The optimum W/S ratio was 0.20 for the addition of Si sludge less than 30 wt.% and W/S ratio should be more than 0.28 for the addition of Si sludge more than 30 wt.%, although there was no practical application in fact.

• Journal of the Korean Geotechnical Society
• /
• v.29 no.1
• /
• pp.23-27
• /
• 2013

The risks of debris flows caused by climate change have increased significantly around the world. Recently, landslide disaster prevention technology is more focused on the failure and post-failure dynamics to mitigate the hazards in flow-prone area. In particular, we should define the soil strength and flow characteristics to estimate the debris flow mobility in the mountainous regions in Korea. To do so, we selected known ancient landslides area: Inje, Pohang and Sangju debris flows. Firstly we measured physical and mechanical properties: liquidity index and undrained shear strength by fall cone penetrometer. From the test results, we found that there is a possible relationship between liquidity index and undrained shear strength, $C_{ur}=(1.2/I_L)^{3.3}$, in the selected areas, even though they were different in geological compositions. Assuming that the yield stress is equal to the undrained shear strength at the initiation of sliding, we examined the flow characteristics of weathered soils in Korea. When liquidity index is given as 1, 1.5 and 3.0, the debris flow motion of weathered soils is compared with that of mud-rich sediments, which are known as low-activity clays. At $I_L=1$, it seems that debris flow could reach approximately 250m after 5 minutes. As liquidity index increased from 1 to 3, the debris flow propagation of weathered soils is twice than that of low-activity clays. It may be due to the fact that soil masses mixed with the ambient water and then highly fragmented during flow, thereby leading to the high mobility. The results may help to predict the debris flow propagation and to develop disaster prevention technology at similar geological settings, especially for the weathered soils, in Korea.

• Geotechnical Engineering
• /
• v.13 no.4
• /
• pp.37-54
• /
• 1997

This paper is to investigate the bearing capacity and the failure mechanism of slope subjected to strip surcharges adjassent to embankment slope of sandy soil. Parametric model tests under plain strain condition were performed by changing width of footing, relative density of slope materials, and position of footing from the crest of slopes. For model tests, Jumunjin standard sand was used as the slope material and its relative density was 45% and 70%, respectively. The angle of slope was formed with 1 : 1.5 and 1 2. Rigid model footings, made of aluminuu were used with their widths of 4, 7, 10 and 12cm. For the position of model footing, position ratios, distance of model footing from the crest of slope divided by footing width, were 0, 0.5, 1, 2, 3, 4, 5. Failure mechanism was observed by using ink colored sands and markers inserted in model slopes. Ultimate bearing capacity obtained from tests was analyzed and compared with limit equilibrium method, limit analysis method and empirical equation. Characteristics of load-settlement curves and failure mechanism were also analyzed and compared with the existing theories. Thus, their effects on ultimate bearing capacity of model footing adjacent to slope were assessed.

• Applied Chemistry for Engineering
• /
• v.29 no.6
• /
• pp.696-702
• /
• 2018

Recently, the current thermal battery technology needs new materials for electrodes in the power and energy density to meet various space and defense requirements. In this paper, to replace the pellet type Li(Si) anode having limitations of the formability and capacity, electrochemical properties of the lithium anode with high density for thermal batteries were investigated. The lithium anode (Li 17, 15, 13 wt%) was fabricated by mixing the molten lithium and iron powder used as a binder to hold the molten lithium at $500^{\circ}C$. The single cell with 13 wt% lithium showed a stable performance. The 2.06 V (OCV) of the lithium anode was significantly improved compared to 1.93 V (OCV) of the Li(Si) anode. Specific capacities during the first phase of the lithium anode and Li(Si) were 1,632 and $1,181As{\cdot}g^{-1}$, respectively. As a result of the thermal battery performance test at both room and high temperatures, the voltage and operating time of lithium anode thermal batteries were superior to those of using Li(Si) anode thermal batteries. The power and energy densities of Li anode thermal batteries were also remarkably improved.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.37 no.7
• /
• pp.865-873
• /
• 2013

The deep drawing and ironing (DDI) process involving the use of a high-capacity horizontal press is used for manufacturing acompressed natural gas (CNG) pressure vessel. However, some variables of the DDI process have been determined based on the experiences of workers, and the short die life needs to be improved for manufacturing the pressure vessel withhighquality and lowcost. In this study, process variables such as the draw ratio, distance between dies, radius of rounding of drawing die, and angle of ironing die are chosen to enhance the reliability and improve the die life based on previous studies and experiences. The draw ratio limits at which no tearing or wrinkling occurs are determined using FEA, and the distances between dies, radius of rounding of drawing die, and angle of ironing die are optimized by the DOE method. The results of the optimal process variables are compared with those of the existing DDI process for verifying their effectiveness.

• The Korean Journal of Rheology
• /
• v.11 no.1
• /
• pp.18-27
• /
• 1999

Predicting the deformation behaviors of sheets in thermoforming processes has been a daunting challenge due to the strong nonlinearities arising from very large deformations, mold-polymer contact condition and hyperelasticity constitutive equations. Nonlinear numerical analysis is always required to face this challenge especially for realistic processing conditions. In this study a 3-D algorithm and the membrane approximation are developed for thermoforming processes. The constitutive equation is expressed in terms of the 2nd Piola-Kirchhoff stress tensor and the Cauchy-Green deformation tensor. The 2-term Mooney-Rivlin model is used for the material model equation. The algorithm is established by the finite element formulation employing the total Lagrangian coordinate. The deformation behavior and the stress distribution results of 3-D algorithm with various point boundary conditions are compared to those of the membrane approximation algorithm. Also, the slip boundary condition and the no-slip boundary condition are applied for the systems that have molds. Finally, the effect of sheet temperatures on the final thickness distribution is investigated for the ABS material.