• 한국지반신소재학회논문집
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• 제22권1호
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• pp.87-96
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• 2023

상부에 준설매립점토층이 존재하고 점토층이 두껍게 분포되어 있는 부산항 신항만에서 측정된 지표침하 값과 층별침하 값은 많은 차이가 있다. 이런 결과의 원인과 해결방안을 찾기 위하여 연약지반 개량에 사용된 층별침하계의 실태, 층별침하계 형식별 특성, 설치방법, 계측 빈도, 계측데이터 관리방안, 결과의 정리 및 분석 등에 대해 고찰해 보았다. 대변형이 발생하는 대심도 연약지반 개량공사에서 스크류타입의 층별침하계의 경우 휨 변형이 다른 형식의 계측기에 비해 적어 망실의 우려도 적고 각 지층별로 천공하여 계측기를 설치하므로 데이터의 신뢰도도 상대적으로 높다. 정도 높은 침하계측 자료의 양이 많을수록 침하분석 정밀도는 높아지므로 표준시방서에서 제시한 계측빈도보다 기준을 강화하여 관리가 필요하다. 층별침하계 계측데이터의 관리는 측점별 지표침하량, 층별침하량, 간극수압계 침하량과 같이 해당 구간의 침하량과 성토고의 경시 그래프 작성하여 관리하는 것이 바람직하다. 침하분석은 압축특성이 다른 다층지반일 경우 층별침하 데이터를 이용하여 각 지층별 압밀특성을 각각 산정하여 침하분석이 이루어지는 게 더 타당하다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 가을 학술발표회 논문집
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• pp.147-158
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• 2001

In general, two methods have been used to predict settlement of soft ground. One method is Terzaghi's one dimensional consolidation theory which gives time-settlement relationship using the standard consolidation test results. The other is forecasting method of ground settlement to be occured in the future using in-situ monitoring data. The above both methods have some defects in application manner or in itself especially in very deep and soft clayey ground. In view of the lessons and experiences of soft ground improvement projects, several techniques were proposed for more accurate theorectical calculation of consolidation settlement as follows ; ① Subdivision of soft ground, ② Consideration of secondary compression, ③ Using the modified compression index, etc. And also, revised hyperbolic fitting method was suggested to minimize the error of predicted future settlement. In addition, revised De-Beer equation of immediate settlement of loose sandy soil was proposed to overcome the tendency to show too small settlement calculation results by original De-Deer equation. And also, considering the various effects of settlement delay in the improved ground by vertical drains, time-settlement caculation equation(Onoue method) was revised to match the tendency of settlement delay by using the characteristics of discharge capacity decreases of vertical drain with time elapse by the pattern of hyperbolic equation.

• 한국지반공학회논문집
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• 제24권6호
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• pp.85-93
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• 2008

대심도 연약지반에 설치되는 말뚝은 말뚝의 길이가 길어져 지반지지력이 크므로 극한 지지력의 확인이 힘들고, 부마찰력에 의해 큰 잔류하중이 발생하기 때문에 하중전이시험을 수행하더라도 정확한 하중전이곡선을 산정하기 어렵다. 본 연구에서는 연약지반에 설치된 PHC 항타 말뚝을 대상으로 선단지지력과 주면마찰력을 분리측정할 수 있고 극한 지지력을 확인하기 용이한 하중전이 양방향 재하시험을 수행하였다. 말뚝설치 직후부터 말뚝변형률을 지속적으로 계측하여 잔류하중을 결정하였다. 잔류하중의 영향을 고려하여 참지지력과 참 하중-변위 곡선을 분석하였다. 이를 바탕으로 잔류하중이 포함된 주면마찰력에 대한 하중-변위 거동모형을 제안하였다. 결과적으로, 점토지반에 설치되는 장대말뚝의 재하실험 결과에 대한 정확한 분석을 위해서는 잔류하중을 고려하여야 한다는 것을 입증하였다.

• 한국지반환경공학회 논문집
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• 제13권6호
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• pp.83-90
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• 2012

일반적으로 심층혼합공법에 의한 점토지반의 개량효과는 물리적 개량효과에 비해서 훨씬 크며 조기에 큰 개량 강도를 얻을 수 있으나, 국내 시공실적이 부족하고 시멘트-점토의 혼합방법에 따른 품질관리에 문제점이 있는 것으로 알려져 있다. 본 연구에서는 시멘트, 모래, 점토의 배합비에 따른 강도특성과 연직MAT의 형태에 따른 연약지반의 개량특성을 파악하기 위해 해성점토를 이용하여 일축압축 강도시험과 모형토조시험을 수행하였다. 일축압축강도 시험을 위한 공시체는 시멘트와 물의 중량비를 기준으로하여 모래를 일정 비율로 혼합하였고, 시멘트는 점토중량대비 각각 10%, 20%, 30%, 40%를 혼합하였고 대상지반토의 함수비는 40%, 60%, 80%로 조정하여 제작하였다. 공시체는 습윤방법을 이용하여 7일, 14일, 28일간 양생하여 양생기간에 따른 일축압축강도시험을 수행하였다. 지지력시험은 모형토조를 제작하고 Mat식으로 개량한 지반을 형성한 다음 개량률에 따른 지지력을 비교하고 연직MAT 장벽 상호간의 간섭효과를 분석하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 가을 학술발표회 논문집
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• pp.577-584
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• 2002

We have employed two methods to remove slime at the end of the sampler in clay layers. The first method is a sampling process that harnesses low pressure to clean up the ground around the sampler tip. The second method, in consideration of a disturbed layer, involves a technique of inserting the sampler 50 cm deep into the ground before cleaning up the verge of the sampler by using high pressure. Physical and mechanical properties of these two methods have been compared and analyzed to investigate how different sampling methods affect degree of disturbance. The first method shows little disturbance since the unconfined compression test results in quite greater E$\_$50//q$\_$u/ in the first method than in the second method. On the other hand, the consolidation test results in a slightly greater compression index in the second method than in the first method, when their indexes are compared in the same depth. This suggests that the second method demonstrates less disturbance than the first method does. It is assumed that the second method may reduce disturbance slightly, However, we suspect that choosing any of the two methods would not obtain a considerable difference in sampling.

• Geomechanics and Engineering
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• 제18권2호
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• pp.189-203
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• 2019

Brine leakage is a common phenomenon during construction facilitated by artificial freezing technique, threatening the stability of frozen wall due to the continual thawing of already frozen domain. This paper takes the frequently encountered soft clay in Wujiang District as the study object, and remolded specimens were prepared by mixing calcium chloride solutions at five levels of concentration. Both the deformation and pore water pressure of frozen specimens during thawing were investigated by two-stage loading tests. Three sections were noted from the changes in the strain rate of specimens during thawing at the first-stage load, i.e., instantaneous, attenuated, and quasi-stable sections. During the second-stage loading, the deformation of post-thawed soils is closely correlated with the dissipation of pore water pressure. Two characteristic indexes were obtained including thaw-settlement coefficient and critical water content. The critical water content increases positively with salt content. The higher water content of soil leads to a larger thaw-settlement coefficient, especially at higher salt contents, based on which an empirical equation was proposed and verified. The normalized pore water pressure during thawing was found to dissipate slower at higher salt contents, with a longer duration to stabilize. Three physical indexes were experimentally determined such as freezing point, heat conductivity and water permeability. The freezing point decreases at higher salt contents, especially as more water is involved, like the changes in heat conductivity. The water permeability maintains within the same order at the considered range of salt contents, like the development of the coefficient of consolidation. The variation of the pore volume distribution also accounts for this.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.1164-1169
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• 2009

Piled raft foundation is commonly used for structure on deep soft soil deposit rather than end bearing piles to control differential settlement. However, it is still expensive for light weight structures. Wing-wall type foundation has been successfully applied to reduce average settlement for light weight structure. This study will further investigate this type of foundation using bench scale experiments on clay and sand. Numerical analysis and approach method are used to verify load settlement curve of wing-wall foundation on experimentally study. Furthermore, normalized settlement curves are applied to define prediction of settlement on wing-wall foundation. In the result settlement on wing-wall foundation can be effectively done by increasing the length of wall instead of number of walls and equation for calculating average settlement can be derived using normalized load settlement curve.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 추계 학술발표회
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• pp.497-508
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• 2006

Busan-Geoje Fixed Link, total length of 8.2km, consist of bridge and immersed tunnel connects Gaduk island, Busan and Jangmokmyon, Geoje, in extension of the $58^{th}$ local road. The immersed tunnel, a total length of 3.7km within Busan-Geoje Fixed Link, was planed first timein domestic but the deep water depth like maximum of 50m with offshore conditions and the 35m thickness of soft clay layer under the immersed tunnel, migth be some problems like the differential settlement during or after works. So it was designed to install SCP(Sand Compaction Pile) column partially to improve the soft ground under the immersed tunnel. In this paper, it is presented to illustrate the design including ground condition under the immersed tunnel, improvement design, upheaval shape and ratio due to SCP test construction.

• Bulletin of the Korean Chemical Society
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• 제23권11호
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• pp.1531-1540
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• 2002

With the invention of the inlaying technique for celadon in the latter half of the 12th century, the Koryo potters reached a new height of artistic and scientific achievement in ceramics chemical technology. Inlaid celadon shards, collected in 1991 during the surface investigation of Kangjin kilns found on the southwestern shore of South Korea, were imbedded in epoxy resin and polished for cross-section examination. Backscattered electron images were taken with an electron microprobe equipped with an energy dispersive spectrometer. The spectrometer was also used to determine the composition of micro-areas. Porcelain stone, weathered rock of quartz, mica, and feldspar composition were found to be the raw material for the body and important components in the glaze and white inlay. The close similarity between glaze and black inlay in the microstructure suggests that the glaze material was modified by adding clay with high iron content, such as biotite, for use as black inlay. The deep soft translucent quality of celadon glaze is brought about by its microstructure of bubbles, remnant and devitrified minerals, and the schlieren effect.

• 한국안전학회지
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• 제14권2호
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• pp.116-121
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• 1999

When plate anchors are embedded in soft clay, they may undergo a deformation under the pressure of sustained load. The critical depth at which the transition from a shallow to a deep anchor takes place depends on the properties of soil. Laboratory model tests were performed for the short-term net ultimate uplift capacity of a circular anchors with respect to various embedment depths and moisture content in saturated kaolinite. The tests have been conducted with the anchor at two different moisture contents. Based on the model test results, empirical relationships between the net load, rate of strain, and time have been developed. In creep tests of kaolinite for load versus ultimate uplift capacity, the displacement of plate anchors rapidly increases during the primary stage but thereafter becomes constant over a period of time.