• 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.

• Journal of the Korean Geotechnical Society
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• v.26 no.12
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• pp.61-70
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• 2010

A series of shaking table tests were conducted to estimate the seismic performance of soft ground deposits improved by stone column. The amplification of acceleration, shear strain, and shear wave velocity were evaluated to compare the seismic response of unimproved ground deposits with that of improved ground deposits. From the test results, it was shown that the stone column can prevent large shear deformation in ground deposits. However, it was also found that the acceleration of improved ground deposits may be amplified more than that of unimproved ground deposits when it was subjected to short periodic seismic wave. The results suggest that it is necessary to perform the ground response analysis with model experiments for both unimproved and improved ground deposits to evaluate the effect of stone column on the seismic performance of improved ground deposits.

• Journal of the Korean Geotechnical Society
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• v.26 no.11
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• pp.47-61
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• 2010

To predict the settlement rate of a ground area that incorporates vertical drains, it is desirable to conduct various kinds of advanced field and laboratory tests for hydraulic properties. However, it is urgently needed to appropriately evaluate the hydraulic properties using the results of conventional soil tests which are extensively used for local practice. To achieve this purpose, a number of CPT dissipation test, laboratory permeability and consolidation tests were performed at five sites in the floodplain of the Nakdong River delta, and the test data were comprehensively analyzed. As a result, it is found that the coefficients of horizontal consolidation ($C_{h,NC}$) and permeability ($k_{h,OC}$) of the clay agreed well with those of the CPT-based methods proposed by Baligh and Levadoux (1986). The values of $C_{h,NC}$ and $k_{h,OC}$ were in the range of $0.4{\sim}3.0\;cm^2/sec$ and $0.40{\sim}2.50\;cm^2/sec$, each of which slightly increases or decreases with depth, respectively. It was also inferred that these trends seem to reflect the depositional environments of the clay.

• Journal of the Korean Geosynthetics Society
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• v.15 no.1
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• pp.47-57
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• 2016

Many researchers reported that artesian pressure exists in thick soft ground of Busan Nakdong river estuary. Artesian pressure in soft ground could affect rate of consolidation, settlement and drainage capasity of prefabricated vertical drain(PVD). This paper investigated consolidation behaviors of soft ground with partially penetrated PVD subjected to artesian pressure. Laboratory tests with 1-dimensional large column equipment and their numerical analyses were carried out. Test results showed that the consolidation settlement of clay ground with artesian pressure was higher than that without artesian pressure. Due to artesian pressure, the dissipation rate of excess pore water pressure was reduced in soft ground with artesian pressure, especially at bottom part of clay ground. Numerical results were in good agreement with experimental test results.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.747-752
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• 2003

This study was carried out to understand the stratigraphy and depositional environment of clayey soils that distributed in the Gadeok-do area, Kimhae plain (Nakdong estuary). For the study, SPT core sampling and magnetic susceptibility analysis were conducted. Soils in study area is classified into five sedimentary facies ascending order; sand/gravel. clay, sand/gravel, clay, interbedded sand and silty clay. Analysis of magnetic susceptibility for Gadeok-do clayey soil reveals that depositional process and environment can be divided into upper, middle and lower layer, and they are closely related to the sea level change since late Quaternary.

• 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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• 2005.03a
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• pp.240-247
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• 2005

In order to analyze effects of strain rate on consolidation characteristics on Busan clay, a series of constant rate of strain(CRS) consolidation tests with different strain rate and incremental loading test(ILT) were performed. From experimental test results, it was found that the preconsolidation pressure was dependent on the corresponding strain rate occurred during consolidation process. Also, consolidation curves normalized with respect to preconsolidation pressure gave a unique stress-strain curve. Coefficient of consolidation and permeability estimated from CRS test had a tendancy to converge to a certain value at normally consolidated range regardless of strain rate. An increase in excess pore pressure without change of total stress was noted on the incremental loading test after the end of loading.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.320-325
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• 2009

The constrained modulus, representative property to evaluate compressibility of soil, is needed to estimate the settlement of ground structure. A series of lab and field cone penetration tests for clayey soil of Busan new-port and Noksan industrial area were conducted to evaluate the estimation method of constrained modulus. Since CPT generates large deformation of ground, it is difficult to correlate the cone resistance with the constrained modulus. Therefore, appropriate correlation between them is essential to estimate the constrained modulus based on CPT results. The test results show that the ratio of the constrained modulus to the cone resistance is inversely proportional with plasticity index. Based on this result, the estimation method of constrained modulus for Busan clay is suggested.

• 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.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.472-472
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• 2015

토양수분은 수문학에서의 물 순환을 비롯한 여러 다양한 자연과학적 분야에 중요한 인자로 활용되고 있다. 본 연구의 대상사면인 지형학적, 토양학적으로 복합적이고, 불균질한 작은 산지사면에서 토양수분의 시공간적 분포에 대한 지형, 토성인자의 영향에 대해 파악하고자 한다. 토양수분은 TDR방식의 모니터링 시스템을 통해 안정적으로 측정이 되었으며, 각 영향인자들은 사면의 지형분석 및 토성분석을 실시하여 확보되었다. 지형인자는 습윤지수, 기여사면면적, 지역적 경사 그리고 토양깊이 인자이며, 토성은 모래, 실트, 점토함량, 가밀도 값을 이용하였다. 사면의 측정된 토양깊이별 토양수분의 시공간적 변동에서의 각 인자와의 상관분석 및 다변량 분석을 통해, 각 영향인자들의 관련성 평가하였다. 사면 전체측정지점들의 토양수분의 시공간적 분포와 영향인자의 상관분석을 통해서 토양수분의 결정에는 지형보다는 토성의 영향이 지배적으로 나타났지만, 모래함량이 높은 토성을 가진 측정지점들에 한해 분석한 결과에서는 지형의 영향은 증가하였고, 토성의 영향은 오히려 줄어들었다. 토양깊이별 상관분석에서는 토양깊이 10cm의 각 인자와의 관련성이 30, 60cm보다 높은 것으로 나타났다. 토양수분변화에 따른 각 인자와의 상관계수 변화는 토양수분이 약 28~32%정도의 포화되기 전의 습윤한 조건일 때, 각 인자들과의 상관성이 증가한 것으로 나타났다.