• Journal of Chest Surgery
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• v.45 no.6
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• pp.380-389
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• 2012

Background: Bovine pericardium is one of the most widely used materials in bioprosthetic heart valves. Immunologic responses have been implicated as potential causes of limited durability of xenogenic valves. This study aimed to determine the effectiveness of decellularization and ${\alpha}$-galactosidase (${\alpha}$-gal) to remove major xenoreactive antigens from xenogenic tissues. Materials and Methods: Recombinant Bacteroides thetaiotaomicron (B. thetaiotaomicron) ${\alpha}$-gal or decellularization, or both were used to remove ${\alpha}$-gal from bovine pericardium. It was confirmed by ${\alpha}$-gal-bovine serum albumin-based enzyme-linked immunosorbent assay (ELISA), high-performance anion exchange chromatography, flow cytometry, 3,3'-diaminobenzidine-staining, and lectin-based ELISA. The mechanical properties of bovine pericardium after decellularization or ${\alpha}$-gal treatment were investigated by tests of tensile-strength, permeability, and compliance. Collagen fiber rearrangement was also evaluated by a 20,000${\times}$ transmission electron microscope (TEM). Results: Recombinant B. thetaiotaomicron ${\alpha}$-gal could effectively remove ${\alpha}$-gal from bovine pericardium B. thetaiotaomicron (0.1 U/mL, pH 7.2) while recombinant human ${\alpha}$-gal removed it recombinant human ${\alpha}$-gal (10 U/mL, pH 5.0). There was no difference in the mechanical properties of fresh and recombinant ${\alpha}$-gal-treated bovine pericardium. Furthermore, the TEM findings demonstrated that recombinant ${\alpha}$-gal made no difference in the arrangement of collagen fiber bundles with decellularization. Conclusion: Recombinant B. thetaiotaomicron ${\alpha}$-gal effectively removed ${\alpha}$-gal from bovine pericardium with a small amount under physiological conditions compared to human recombinant ${\alpha}$-gal, which may alleviate the harmful xenoreactive immunologic responses of ${\alpha}$-gal. Recombinant ${\alpha}$-gal treatment had no adverse effects on the mechanical properties of bovine pericardium.

• Journal of the Korean Geosynthetics Society
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• v.10 no.2
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• pp.67-72
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• 2011

CMDS (Coal Mine Drainage Sludge) is mainly generated from acid mine drainage during physicochemical treatment or electrical purification. CMDS is well worth considering on recycling possibilities in various areas. This research applies the liner and cover materials using waste disposal landfill generally to treat acid mine drainage sludge. In this Part I of the two parts paper, physico-chemical characteristics of CMDS, bentonite and cement to prepare the liner have been identified using XRD, XRF, FESEM. In addition, combining their physicochemical characteristics, the optimum mixing ratio has been determined to be 1: 0.5: 0.3 for CMDS: bentonite: cement by the batch tests. Initial permeability of CMDS was $7.10{\times}10^{-7}cm/s$. Through the leaching test, it was confirmed that its mixture was environmentally safe. In the Part 2, a large-scale Lysimeter was used to simulate the effects of the layer on the freeze/thaw for evaluation on field applicability and stability.

• Geotechnical Engineering
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• v.14 no.4
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• pp.151-162
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• 1998

The compressibility and the permeability of organic soil are so high that they cause many engineering problems when constructing a structure on the soil. If the organic content of the soil could be reduced by any applicable engineering technique, the engineering properties of the soils can be improved to some extent. The purpose of this study would thus be focused on how to decrease the amount of organic matters by applying aerobic biodegradation for eliminating post-construction settlement problems. To enhance the aerobic decomposition, oxygen was supplied to the soil samples prepared by the mixture of kaolinite and sawdust as organic matter. The dissolved oxygen and the organic content of the soil samples were measured, in accordance with the passage of time through the bests. As oxygen suppliers, HaOa liquid and pure oxygen gas were compared to meet the requirement of the test purposes. Newly manufactured oedometer with the diameter of 130 mm and the height of 300 mm was used for 100 days to perform the compressibility tests for the soils. Based on the results of this experiment, the oxygen gas-treated samples with nutrient settled 30% more than the samples untreated. This confirmed the efficiency of the aerobic biodegradation. $NaNO_3$ added into the soils as nutrients was proved more effective than $K_2HP0_4$. To confirm the activity of micro-organisms, sodium azide was also added to the soils.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.217-225
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• 2003

An experimental study was conducted to evaluate the smeared effect due to mandrel penetration into soft ground for a vertical drain installation. Laboratory tests were performed to investigate the formation of a smear zone, the variations of strength, and the consolidation characteristics in the disturbed zone using two types(CL at Yangsan site and OH at Pohang site) of soft clayey soils. The smear zone effect was evaluated focusing on mandrel shape, mandrel size, penetration speed, and ground condition. Based on laboratory test results, the diameter of the smear zone$(d_s)$ ranged from 3.08 and 3.92 times that of mandrel$(d_m)$. It was also found that the $(d_s/d_m)$ value of the circular shape of the mandrel is smaller than those of square and rectangular shapes. The value of $(d_s/d_m)$ decreased with larger mandrel size, lower penetration speed in the CL soil, and higher penetration speed in the OH soil. However, natural water content was minimally affected by $(d_s/d_m)$. Respectively, the coefficients of horizontal consolidation$(C_{hs})$ and horizontal Permeability$(K_s)$ of smear zone ranged from 0.81 to 0.87 times, and 0.73 to 0.83 times those of the undisturbed zone. Based on this study, the values of $C_{hs}, K_s$ and unconfined compressive strength$(q_{us})$ in the smear zone were the lowest at close vicinity of the mandrel and increased linearly with distance from the mandrel. Further, the $(q_{us})$ varied from 0.5 to 0.9 times that of the undisturbed zone strength.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.5
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• pp.1073-1082
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• 2015

The behavior of the unsaturated soil slope can be influenced by the various factors such as the hydraulic characteristics, the mechanical characteristics, the coefficient of conductivity, the stratifications, the rainfall conditions i.e. the rainfall intensity, the rainfall pattern, the duration time of the rainfall and the antecedent rainfall etc. It is known that the slope failure is influenced greatly by the antecedent rainfall rather than the rainfall condition at the failure time, so the antecedent rainfall is supposed to be a very important factor in slope stability analysis among these factors. To predict and to prevent the slope failure by the rainfall, the distribution of the matric suction by the antecedent rainfall must be considered first of all and the slope stability analysis should be carried out by considering the successive rainfall characteristics. In this research, 3 samples with different quantity (5%, 10%, 20%) of silts were prepared and the SWCC (Soil-water characteristic curve) tests were carried out and the associated parameters were analyzed. After analyzing the distribution of the matric suction and the change of the mechanical characteristics such as the stress and the strength when applying the antecedent rainfall for one month and the successive intensive rainfall for 12 hours, the slope stability analyses were carried out numerically. And the influence of the antecedent rainfall for one month and the SWCC on the stability of a slope were compared and analyzed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.5
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• pp.485-500
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• 2020

Due to various advantages such as small facilities, ease of construction and so on, the grouting technology which is widely used in construction field has developed remarkably compared with the past. However, the efforts to improve the homogeneity of quality, long-term durability and environmental problems have been continued. In recent years, new grouting method has been developed in order to solve problems such as low strength, durability and leaching phenomenon of liquid glass (sodium silicate) grouting material in Korea. A newly developed method integrates the injection material with the ground by the self-healing material of crystallization growth type. For this reason, it is known that improvement of the durability and water quality of the ground, prevention of leaching, and environment friendliness can be expected. The present study applied a newly developed method to test sites and verified its effect such as injection range, improvement effect, waterproofing performance and so on. Standard penetration test, field permeability test, borehole shear test, pressuremeter test and pH test were conducted, and the results were compared between before and after developed method application. As results of tests, the field applicability and improvement effect of developed method were proved to be excellent.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6C
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• pp.213-220
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• 2011

Fines such as silt or clay are usually mixed with granular particles in natural or reclaimed soils which are slightly cemented. Such fines contained within weakly cemented soils may influence permeability and also mechanical behavior of the soils. In this study, a series of unconfined compression tests on weakly cemented sands with fines are carried out in order to evaluate the effect of fines on unconfined compressive strength (UCS) of cemented soils. Two different cement ratios and fine types were used and fine contents varied by 5, 10, and 15%. Two types of specimens were prepared in this testing. One is the specimen with the same compaction energy applied. The other is the one with the same dry density by varying compaction energy. When the same amount of compaction energy was applied to a specimen, its density increased as a fine content increased. As a result, the UCS of cemented soils with fines increased up to 2.6 times that of one without fines as an amount of fines increased. However, when the specimen was prepared to have the same density, its UCS slightly decreased and then increased a little as a fine content increased. Under the same conditions, a UCS of the specimen with silt was stronger than the one with kaolin. As a cement ratio increased, a UCS increased regardless of fine type and content.

• International Journal of Highway Engineering
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• v.10 no.4
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• pp.189-198
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• 2008

Generally, UFF A(Ultra Fine Fly Ash) has merit that advances a greater concrete workability and activates a greater pozzolanic reaction than common fly ash due to its ultra fine particle size. These properties enhance concrete durability by reducing permeability and increasing resistance of alkali silica reaction(ASR) and sulfate attack, etc. Due to these reasons, UFFA can be used in a rapid setting concrete. The purpose of this study is to develop and evaluate the rapid setting concrete with UFF A as a repair material for early-opening-to-traffic. In previous studies, if only UFFA is added to the rapid setting concrete mixture, pozzolanic reaction doesn't happen actively. Therefore, in this study, the chemical and physical tests were performed for rapid setting concrete with UFFA including calcium hydroxide and the activity of pozzolanic reaction was evaluated. Finally, the effectiveness of this mixture on enhancing concrete durability was investigated. As results, adding UFF A decreased the water/cement ratio of concrete, and compensated the reduced portion of the early strength of concrete. Also, rapid setting concrete with UFFA including calcium hydroxide activated a greater pozzolanic reaction than normal-UFF A concrete. As calcium hydroxide increases, electrical indication of concrete's ability to resist chloride ion penetration is promoted significantly.

• The Journal of Engineering Geology
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• v.25 no.3
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• pp.377-385
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• 2015

We constructed a model test apparatus to evaluate the dependence of the saturation velocity (V_s) in soils on rainfall intensity (I_R). The apparatus comprises a soil box, a rainfall simulator, and measuring sensors. The model grounds (60 cm × 50 cm × 15 cm) were formed by Joomunjin standard sand with a relative density of 75%. The rainfall simulator can control the rainfall intensity to reenact the actual rainfall in a soil box. Time Domain Reflectometer (TDR) sensors and tensiometers were installed in the soils to measure changes in the volumetric water content and matric suction due to rainfall infiltration. During the tests, the soil saturation was determined by raising the groundwater table, which was formed at the bottom of the soil box. [Please check that the correct meaning has been maintained.] The wetting front did not form at the ground surface during rainfall because the soil particles were uniform and the coefficient of permeability was relatively high. Our results show that the suction stress of the soils decreased with increasing volumetric water content, and this effect was most pronounced for volumetric water contents of 20%-30%. Based on a regression analysis of the relationship between rainfall intensity and the average saturation velocity, we suggest the following equation for estimating the saturation velocity in soils: V_savg (cm/sec) = 0.068I_R (mm/hr).

• Journal of the Korean Geotechnical Society
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• v.31 no.6
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• pp.45-58
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• 2015

The aim of this study is to suggest a semi-empirical equation for estimating the hydraulic conductivity of sands using geoelectrical measurements technique. The suggested formula is based on the original Kozeny-Carman equation; therefore varying factors affecting the Kozeny-Carman equation were selected as the testing variables, and six different sands with varying particle sizes and particle shapes were used as the testing materials in this study. To measure both hydraulic and electrical conductivities, a series of constant head permeameter tests equipped with the four electrodes conductivity probe was conducted. Test results reveal that the effects of both pore water conductivity and flow rate in relation between hydraulic conductivity and formation factor (=pore water conductivity / measused conductivity of soil) of tested materials are negligible. However, because the variations of hydraulic conductivity of the tested sands according to particle sizes are significant, the estimated hydraulic conductivity using the formation factor varies with particle sizes. The overall comparison between the measured hydraulic conductivity and the estimated hydraulic conductivity using the suggested formula shows a good agreement, and the variation of hydraulic conductivity with varying Archie's m exponents is smaller compared with varying porosities.