• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.27-37
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• 2007

The purpose of this study is to propose a method to predict the minimum curing time of early age concrete required to prevent frost damage. Tests were performed to examine major factors, which affect the compressive strength of concrete frozen at early ages and investigate the source of frost damage at early age concrete. The results from the tests showed that the loss rate of compressive strength decreases as the beginning time of frost damage was delayed and water-cement ratio was lower. In addition, the test results also showed that concrete made with type III cement was less susceptible to frost damage than concrete made with ordinary Portland cement and frost damage occurred through the formation of ice lenses. When early age concrete is being damaged by frozen, a phase transition into ice of free water presented at the capillary pores of the concrete gives a reason for the decrease of compressive strength. Accordingly, the frost resistance of fresh concrete can be determined based on the saturation degree of the capillary pores. The method to predict the minimum curing time was suggested using the concept of critical saturation degree of the capillary pores.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1177-1181
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• 2010

Unsaturated soil can describe soil particles, air-water and contact face between air and water. The providing a simple method to predict water content in Geotechnical mechanics is very important. In this experiment, DIP (Digital Image Processing) and electrical resistivity techniques were used simultaneously to predict the saturation degree, and the results of two techniques will be compared each other to get conclusion. The experiment was carried out for Jumunjin standard sand. The picture of experimental column of soil and water was taken at different times, then using DIP technique to measure Color number-the height of capillary in soil column. At the same time, measure electrical resistivity of the soil.

• Journal of the Korean Geotechnical Society
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• v.24 no.6
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• pp.27-35
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• 2008

At low normal stress levels tensile strength of sand varies with either saturation or suction of soil in an up-and-down manner with a peak tensile strength that can occur at any degree of saturation. A theory that accurately predicts tensile strength of wet sand is presented. A closed form expression for tensile strength unifies tensile strength characteristics in all three water retention regimes: pendular, funicular, and capillary. Three parameters are employed in the theory; namely, the Internal friction angle (at low normal stress) ${\phi}_t$, the inverse value of the air-entry pressure ${\alpha}$, and the pore size spectrum parameter n. It is shown that the magnitude of peak tensile strength is dominantly controlled by the ${\alpha}$ parameter. The saturation at which peak tensile strength occurs only depends on the pore size spectrum parameter n.

• Geomechanics and Engineering
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• v.30 no.2
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• pp.211-218
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• 2022

This study characterizes Proctor and geophysical properties in a broad range of grading and fines contents. The results show that soil index properties such as uniformity and fines plasticity control the optimum water content and peak dry unit trends, as well as elastic wave velocity. The capillary pressure at a degree of saturation less than S = 20% plays a critical role in determining the shear wave velocity for poorly graded sandy soils. The reduction in electrical resistivity with a higher water content becomes pronounced as the water phase is connected A parallel set of compaction and geophysical properties of sand-kaolinite mixtures reveal that the threshold boundaries computed from soil index properties adequately capture the transitions from sand-controlled to kaolinite-controlled behavior. In the transitional fines fraction zone between F_F ≈ 20 and 40%, either sand or kaolinite or both sand and kaolinite could dominate the geophysical properties and all other properties associated with soil compaction behavior. Overall, the compaction and geophysical data gathered in this study can be used to gain a first-order approximation of the degree of compaction in the field and produce degree of compaction maps as a function of water content and fines fraction.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.6
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• pp.575-593
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• 2012

This paper briefly introduces the scope and objectives of SKB Task 8, which is an international cooperative research project. In addition, the hydraulic behaviors of bentonite buffer focusing on the interactions between bentonite and a rock mass with a joint were investigated using TOUGH2 code as part of a sub-mission of Task 8a. The effects of a rock joint and high capillary pressure of bentonite on the re-saturation properties and pressure distribution in a buffer were identified and successfully incorporated in the TOUGH2 code. Based on the numerical results, it was found that the speed of re-saturation in bentonite surrounded by a rock mass with a joint is 2.5 to 12 times faster than that in a condition without a rock joint, while the degree of saturation in the lower part of the buffer material is generally higher than in the upper part in both the cases of with and without a joint. It can be anticipated that the results obtained from this study can be applied to an estimation of the full saturation time and a determination of optimum thickness with regard to the design of the bentonite buffer in a high level waste disposal system.

• Proceedings of the SCSK Conference
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• 2003.09a
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• pp.162-177
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• 2003

It has been known that the color of skin reflects the blood flow within. In lips, the capillaries close to the skin surface are numerous; hence lips are redder than the rest of face. However, dermatological research on lips is not as advanced as research on facial or body skin, and little was known about the relationship between relatively dull-colored lips and skin blood flow. The physiological differences between colorful and dull-colored lips were studied by a two-dimensional laser Doppler blood flow analyzer, a spectrometer for the measurement of the degree of oxygen saturation, and a confocal microscope for observing inside lips non-invasively. Dull-colored lips and the corner of lips (dull-colored compared to the center) showed relatively poor blood flow and lower oxygenated hemoglobin. It was found that colorful lips (generally the young) had a blood flow that tended to run straight in parallel with the skin surface. This unique blood-capillary structure can express clear red blood. Those with dull-colored lips had lost this unique structure. Their blood ran perpendicularly from the deep of the skin and down back again into the deep part as like the blood circulation patterns of facial skin. Therefore, the lips of the latter group had fewer blood capillaries near skin surface in the lips than that of the colorful-lips group. A lipstick containing a-glucosyl-hesperidin, which is derived from certain citrus fruits and can enhance blood circulation, was applied for evaluating its effects. Blood flow was increased 30 min after the application. After two weeks of daily application, the lips' condition became noticeably less dull. These findings suggest that the decrease of blood flow in dull-colored lips is caused by the loss of the unique capillary structure and the use of the lipstick to increase blood flow can give a vivid color to lips.

• Journal of the Korean Geotechnical Society
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• v.32 no.1
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• pp.55-62
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• 2016

This study presents the numerical results of soil-water characteristic curve for sandy soil by pore network model. The Jumunjin sand is subjected to the high resolution 3D X-ray computed tomographic imaging and its pore structure is constructed by the web of pore body and pore channel. The channel radius, essential to the computation of capillary pressure, is obtained based on the skeletonization and Euclidean Distance transform. The experimentally obtained soil-water characteristic curve corroborates the numerically estimated one. The pore channel radius defined by minimum radii of pore throat results in the slightly overestimation of air entry value, while the overall evolution of capillary pressure resides in the acceptable range. The relative permeability computed by a series of suggested models runs above that obtained by pore network model at high degree of saturation.

• Tunnel and Underground Space
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• v.26 no.3
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• pp.212-219
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• 2016

The sprayable waterproofing membrane is installed between shotcrete to provide crack bridging and hence prevent flow of liquid water as a waterproofing system. Because of its material characteristics, the sprayable membrane can be constructed at more complex structure than sheet membrane. The main component of the sprayable waterproofing membrane is a polymer-based material, therefore, moisture can migrate through sprayable waterproofing membrane materials by capillary and vapor diffusion mechanisms. The moisture transport mechanisms can have an influence on the degree of saturation and may influence the pore pressure and risk of freeze-thaw damage on concrete linings and membrane. In this study, long-term hygrothermal behavior was simulated with considering moisture transport and long-term effects on saturation of tunnel linings. From the simulation, due to water absorption and vapor transport properties of sprayable membrane, change of relative humidity and water content in tunnel lining can be evaluated.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.175-183
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• 1999

Recently, problems related to vibrations of decomposed granite soils have acquired increasing attention in Korea because those soils cover approximately one third of the country. Both resonant column and cyclic triaxial test were performed to investigate deformation characteristics of unsaturated and cement-mixed decomposed granite soils in Suwon region. The important soil parameters in this respect are the shear moduli, dynamic moduli of elasticity and damping ratios. The dynamic parameters are influenced by variables such as strain amplitude, ratio of loading cycles, and degree of saturations, etc. Test results and data have shown that the optimum degree of saturation to the maximum shear modulus due to a capillary menisci effect was about 17~18 % at low strain amplitude and 10~15 % at intermediate strain amplitude. This paper suggests the range of threshold strain and mean shear modulus of decomposed granite soils in Suwon region. It also proposed the empirical relationship between the dynamic parameters for cement-mixed and non-mixed decomposed granite soils.

• Journal of the Korea Concrete Institute
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• v.20 no.2
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• pp.131-138
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• 2008

Humidity and strain were estimated for understanding the relation between humidity change by self-desiccation and shrinkage in high-performance concrete with low water binder ratio. Internal humidity change and shrinkage strain were about 10%, 4% and $320\times10^{-6}$, $120\times10^{-6}$ respectively on concrete with water binder ratio 0.3, 0.4 and from the results, humidity change and shrinkage represented the strong linear relation regardless of mixture. For specifying the relation on internal humidity change and autogenous shrinkage strain, shrinkage model was established which is driven by capillary pressure in pore water and surface energy in hydrates on the assumption of a single network and extended meniscus in pore system of concrete. This model and experimental results had a similar tendency so it would be concluded that the internal humidity change by self-desiccation in HPC originated in small pores less than 20 nm, therefore controlling plan on autogenous shrinkage might be focused on surface tension of water and degree of saturation in small pore.