• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.361-368
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• 2000

In other to examine the compressibility characteristics of cohesive soils in the mouth of the Nakdong river, the oedometer tests were peformed on undisturbed and reconstituted samples obtained by continuous boring typically at 3 different sites. It is meaningful to compare the consolidation behavior of natural clays with a reference state because the natural clays are depending on the stress history, sedimentary environment and geological history. In this study, the insitu state of the Pusan clays was investigated using the concepts of ISL(Nagaraj, 2000) and ICL and SCL(Burland, 1990). And for the purpose of confirming the existence of the underconsolidated clays, a standpipe type piezometer test and a dissipation test by piezocone were performed at their sites. Consequently, the Pusan clays were evaluated as normally consolidated clays.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.341-348
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• 2003

In the estuary of Nagdong River thick marine sediments were deposited by the Holocene marine transgression. The sediments largely consist of silty clay, which is called Pusan clays in the geotechnical field. This paper presents engineering geological characteristics of Pusan clays in Beombangdong area. Overall geological environmental changes based on several geological properties are discussed and synthesized as Geological Environmental Zones. And also, engineering properties of the clays in laboratory and field are discussed and synthesized as Engineering Zones. Two zones are correlated and engineering characteristics are evaluated in view of engineering geology.

• Economic and Environmental Geology
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• v.28 no.1
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• pp.1-8
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• 1995

The smectite-rich clays were found locally in Paleozoic calcareous sedimentary rocks in the Samcheok area. Their occurrences were investigated in detail, and the physico-chemical properties of the clays were also determined by X-ray diffraction, chemical analysis, thermal analysis and cation exchanging experiment. The smectite clays occur as the fissure filling dyke developed in calcareous sedimentary rock and as alteration products of intrusive rhyolite. Most of clays occur at the contact between the sedimentary rock and the rhyolite, and the alteration zone was observed only in rhyolite body close to the contact. Judging from their occurrences, it is believed that the smectite-rich clays in this area were formed by the hydrothemal alteration. The smectite clays from the area are mainly composed of Ca-montmorillonite, and associated with small quantities of quartz, opal-CT and feldspar. The montmorillonites from this area are lower in Fe content, and higher in exchangeable Ca ion, compared to those of bentonite from the Yangnam-Yeongil area.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.295-307
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• 2002

In the Nakdong River plain a very thick clayey soils are covered widely. Since the early 1990's, some huge reclamation projects have been performed for the development of industrial and residential complexes and so on. Despite a large number of soil investigations have been carried out for the projects, the geotechnical properties have never been elucidated well, so that the settlements of the ground due to the mischaracterized properties were greatly underestimated. Therefore, it has been needed to evaluate definitely the characteristics of the clayey soils, particularly for the compressibility characteristics to help understand the settlement behavior. For the compressibility characteristics of the Pusan clays, physical index and consolidation tests were conducted on the reconstituted and undisturbed samples. Using the result of physical index, the Pusan clays could be divided into two different units, which have different depositional environments. According to the concepts of Burland (1990) and Nagaraj et. al. (1990), the intrinsic state line and field compression curve of the Pusan clays could be established. It could be found from their concepts that the Pusan clays are under the cemented and young normally consolidated state and largely consisted of two units. The cementation of the clays was as well identified by compression index ratio (Tsuchida et. al.,1991) and sensitivity (Leroueil et. al.,1983).

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.530-535
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• 2006

The Pusan clays are soft and thick deposits and in some places, they reach even up to 50-70m. So, the pile foundations are inevitable in almost all cases. But they are significantly expansive when the length of the pile reaches about 70m. In this study, a comprehensive parametric study has been carried out in order to reduce the pile length and number of piles required in turn the cost of the foundation for particular building. A belled shaft pile has been optimized for a typical soil profile using the PLAXIS (FEM code). These results have shown a new direction of the pile foundation in Pusan, Korea. The results including the variation of contact pressures at the bottom of the bell, optimization of the angle of the bell and height of the bell in terms of the diameter of the shaft. And also, the design curves have been generated so that they can be directly used for design of belled shaft foundations. However, the structural strength criterion is being checked in the concerned laboratory.

• Journal of the Korean GEO-environmental Society
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• v.11 no.3
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• pp.43-51
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• 2010

In the downstream areas of the Nakdong river, Pusan clays are commonly found and thickness may reach to maximum of 100m. From geological point of view, Pusan clay are characterized as holocene clays, deposited for approximately 20,000 years ago. Recently, there have been many construction projects based on these soft ground areas. It is needed to know clearly soil properties of the areas for design and safety analysis, especially undrained shear strength of soft clays. However, Pusan clay have not been studied systematically because the clay layers are usually very deep, having high sensitivity characteristic. In this study, undisturbed UD samples obtained from the downstream areas of the Nakdong river were researched using laboratory tests (CthUE, CKcUC, CIUC, UU and UC) and in-situ tests (Field Vane, CPTu). The undrained shear strength characteristics of the samples were depicted using stress-strain relationship.

• Journal of the Korean Geotechnical Society
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• v.22 no.11
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• pp.133-142
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• 2006

Pusan clay, which is distributed in the Nakdong River estuary, is unusually soft and thick compared with other clays in the world. Because the consolidation settlement of the clay was significantly underestimated in several recent reclamation projects, it has been emphasized particularly on the need of studying the permeability characteristics. This study carries out vertical and horizontal permeability tests on undisturbed and consolidated samples from two sites of the area. The results of the study show the peculiar permeability anisotropy and the relationships with other indexes on Pusan clay and also comparison with those of other world clays.

• Korean Journal of Materials Research
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• v.23 no.7
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• pp.366-372
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• 2013

Flexible polyurethane/clay porous nanocomposite foams were synthesized using natural and organically modified montmorillonite clays such as bentonite, closite 10A and closite 30B. The content of nanoclays was varied from 1 to 5 wt% of polyol. Dispersion of clay in Polyurethane(PU) matrix was investigated by X-ray diffraction(Cu-$K{\alpha}$ rays of wavelength $1.54{\AA}$) using an X-ray diffractometer. Also, we determined that the thermal resistance of PU foam increased with added clay, compared to that of pure PU foam. The cell size and the fraction of open cells of the precursor foam were controlled by the addition of clay to the polyurethane foam. Modified clays were found to be more efficient cell openers than the unmodified clay. In addition, the tensile strength and elongation of the polyurethane/clay porous nanocomposites were examined. Increasing clay content increased the mechanical properties of the composites, such as tensile strength, and elongation at break. However, increasing the content over 5 wt% deteriorated the properties of the composites. We found that the nanofillers(bentonite, closite 10A and closite 30B) improved the thermal stability of the nanocomposite foam. The nanocomposite foam containing 3 wt% of closite 30B exhibited the best tensile strength and thermal stability.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.10a
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• pp.57-64
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• 1998

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.391-398
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• 2000

The index properties of cohesive soils play an important role to examine entire tendency of soil properties. Especially, the Atterberg limits have a good correlation with compression and shear strength of cohesive soils. However, these values strongly depend on their testing methods. In this study, for Pusan clays the Atterberg limits were peformed under different conditions; for example, four kinds of specimen preparation, two kinds of testing equipment, and four kinds of estimating method. And a laboratory vane test was peformed to compare the undrained shear strength with that of the fall cone test. As experimental results, the value of liquid limit performed for oven-dried sample, followed in ASTM D4318, underestimated by about 10% compared to those of another three methods, irrespective to the used equipments. But the value of plastic limit was not influenced by sample preparation methods and equipments. The liquid limits by one-point methods(Leroueil et al., 1996; Nagaraj et al., 1981) were agreed well with those of different methods. Finally, the undrained shear strength by laboratory vane test was relatively larger than that of fall cone test, and the relationship between both showed a bad trend.