• Geomechanics and Engineering
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• 제2권2호
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• pp.107-123
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• 2010

Ground settlements and pore pressure changes were monitored around a shallow tunnel constructed in clay till during the excavation and primary lining installation. The settlements above the tunnel continued to develop for up to 100 days after the primary lining installation. Triaxial compression tests were carried out to estimate the short-term and long-term deformation characteristics of the till. Numerical simulation was conducted to history match the field measurements, and thus, to quantify the settlements induced by ground stress relief, consolidation and creep. It was found that the surface settlements due to ground stress relief, consolidation and creep are 17, 12 and 71% of total settlement (about 44 mm), respectively. In addition, early installation of rigid concrete lining could be an effective means to reduce the settlement due to creep.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2007년 가을학술발표회
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• pp.692-700
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• 2007

There are several types of foundations for light-weight structures, such as low story buildings, on soft clay deposits. Those foundations, such as piled raft, compensated foundation, mat foundation, floating foundation are commonly used rather then end-bearing piles to get more benefits on the construction and cost savings. In this study, settlement behaviors are computed and compared for several types of foundations on soft clay deposits. Also, theoretical expressions of parameters for piled raft system were provided with co-relations for design purposes. The predictions of settlements of piled rafts foundation are proposed based on the pile dimensions and design loads. From this study, the piled raft foundations is more benefits for reducing the settlement of clay deposits, and it is found that the piled raft system is applicable and effective on thick clay deposits, and that differential settlements of the foundation should be managed by designing the configuration of pile lengths.

• Geomechanics and Engineering
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• 제14권1호
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• pp.43-50
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• 2018

Applicability of constructing piled raft foundations on soft clay has been given attention in recent years. Lack of sufficient stiffness for soil and thus excessive settlements to allow higher contribution of piles is the major concern in this regard. This paper presents a numerical investigation of performance of piled-raft foundations on soft clay with focusing on a case study. A 3D FEM numerical model is developed using ABAQUS. The model was calibrated by comparing physical and numerical modeling results of other researchers. Then the possibility of using piled-raft system in construction of foundation for a water storage tank in Sarbandar, Iran is assessed. Soil strength parameters in the numerical model were calibrated using the instrumentation data of a heavily instrumented preloading project at the construction site. The results indicate that choosing the proper combination of length and spacing for piles can lead to acceptable differential and total settlements while a high percentage of total bearing capacity of piles can be mobilized, which is an efficient solution for the project. Overall, the construction of piled-rafts on soft clays is promising as long as the total settlement of the structure is not imposing restrictions such as the common 25 mm allowable settlement. But instead, if higher allowable settlements are adopted, for example in the case of rigid steel tanks, the method shall be applicable with considerable cost savings.

• 한국지반공학회논문집
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• 제19권1호
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• pp.111-120
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• 2003

본 연구에서는 점성토지반의 침하량 평가에 보다 적합한 새로운 응력경로시험을 소개하였다. 새로운 시험기법에서는 배압평형과정을 채택함으로써 특정 응력경로상의 모든 점에 대응하는 변형특성을 하나의 시험을 통해 파악할 수 있다. 따라서, 제안된 시험기법을 적용하는 경우, 응력경로법의 실용적인 적용을 위해 필요한 지반의 전반적인 변형거동을 몇 개의 시험만으로 예측할 수 있으며 나아가 기존의 시험기법으로는 수행이 불가능했던 이방적 압밀응력 경로에 대한 변형거동의 평가 역시 실험적으로 가능해진다. 이와 함께 본 연구에서는 성형 카올리나이트 시료에 대해 다양한 응력경로시험을 수행하여 제안된 시험기법의 실험적 적용성을 확인하였으며, 그 결과를 활용하여 전반적인 변형거동과 침하량을 평가하는 실제 과정을 제시하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 연약지반처리위원회 학술세미나
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• pp.70-77
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• 1999

Consolidation settlements on soft clay are often large and potentially damaging to structures. Currently, large-scale projects are in progress in Korea. These structures will be constructed on both thick and soft clay layers, and so the accurate evaluation of magnitude of settlement is required at every step in design and construction. Especially, secondary compression play an important role in consolidation settlements on soft clay. Generally, the magnitudes of secondary compression are evaluated by laboratory and in-situ consolidation tests or by empirical $C_{a/}$ $C_{c}$ relationships. The empirical $C_{a/}$ $C_{c}$ may not be only economical, but a fast and powerful tool in estimating secondary consolidation settlement. However, databases of the $C_{a/}$ $C_{c}$ relationship for sites in Korea are currently insufficient. The purpose of this study is to investigate the relationship of $C_{a/}$ $C_{c}$, on marine clay near the southern sea in Korea. In this study a series of incremental loading consolidation tests (measuring base pore water pressure) are performed. It was found that the $C_{a/}$ $C_{c}$ on undisturbed marine clay equaled 0.0397. This value is similar to the value proposed by Mesri and Castro(1987) for inorganic clay and silt. and silt. and silt.

• 한국지반환경공학회 논문집
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• 제20권1호
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• pp.13-17
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• 2019

This paper presents case history of railway embankment excess settlement on soft clay during service in southern region of Korea. A lot of field observations show that the measured settlements are a lot larger than settlements actually calculated in this area. Back analysis is carried out to verify the soil parameters which are intended to investigate in the subsurface exploration phase and later in a laboratory test program. Recommendations and causes for the engineering practice are suggested to review the determination of excess settlements and, consequently, to improve the settlement prediction. This enormous discrepancy is due to the passing over secondary consolidation, and the design filling did not meet to real construction filling. Immediate settlement could be subsidiary factor of excess settlement.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.445-454
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• 2006

Myungji Housing Complex is located in the Nakdong River plain in which the Busan soft clays are developed. It has thick soft soil laver of about GL(-)50m including loose sandy layers, upper and lower clayey layers. The clayey layers have been being consolidated since the land reclamation was completed to build the place for Housing Complex(Apartment) in 1997. Therefore, as one of a series of advance preparations of this project, study was carried on the geotechnical characteristics under the foundation The first part of this paper represents a brief geological history. Then, geotechnical characteristics of clay was analyzed in the classical developments in soft clay. They were based on the geotechnical data obtained by site investigations performed from 1992 to 2005. Finally, we evaluated the average degree of consolidation at this point in time and the residual settlements of upper clayey layer using dissipation and oedometer tests for this project

• 한국지반공학회지:지반
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• 제13권2호
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• pp.137-154
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• 1997

한계상태설계법상에서 말뚝기초는 상부구조물의 안정성과 공용성에 근거하여 지지력과 침하 량을 만족하도록 설계되어야한다. 본 논문에서는 공용성을 검토하기위해 과압밀된 점토지반에 위치한 9본의 군말뚝과 2본의 단말뚝에 대하여 실무에서 많이 이용되고 있는 예측식과 현장에서 수행한 피조콘 자료를 이용하여 침하량을 산정했다. 지반에 따라 공간적으로 변화하는 탄성계수가 침하예측에 미치는 영향을 간략히 조사했다. 예측방법으로는 단순탄성론적 예측식 인 베직법 (Vesic's method)과 풀러스법 (Poulos'B method)을 이용했으며 산정된 침하량을 실지 말뚝재하실험을 통해서 계측한 것과 비교한 결과 대부분 과다하게 예측했고 지반의 탄성계수를 직선적으로 가정한 같파는 침하계산에 큰 영향은 미치지 않는 것으로 판단되었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1992년도 가을학술발표회 논문집
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• pp.11-26
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• 1992

An attempt has been made to summarize some of the unique geotechnical problems encountered during construction of a few large man-made islands recently completed off the coast of Osaka Bay, Japan. Large settlements appear to be the most serious problem both during and after construction. Settlements due to consolidation of a thick layer of soft alluvial clay that constitutes seabed seem to virtually cease within a relatively short period of time when vertical drains are installed adequately prior to fill placement. Settlements due to compression of underlying thick diluvial deposits consisting of layers of stiff clays interbedded with coarse-grained soils, however, continue over a prolonged period of time and call for special provisions for structures built on the artificial islands to cope with relatively large future settlements. Although accurate settlement prediction is not possible, it is both technically and economically feasible, nevertheless, to construct large-scale islands. Partjcularly attractive and promising is creation of sizable new areas for various purposes, immediately adjacent to highly-developed, densely-populated cities situated along the coast such as those around Osaka Bay.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 준설 및 환경매립에 관한 학술세미나
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• pp.35-48
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• 1999

낙동강은 그 하구 근처에서 김해평야하고 부르는 델타지역을 형성하였다. 김해평야에 퇴적된 점성토는 다른 나라의 점토층에 비해 유달리 두껍다 (최대 60m). 이 지역의 일부는 새로운 공업단지의 개발을 위해 연직 배수재를 설치한 후 평균 5-7m의 높이로 매립하였다. 연약 지반 위에 매립작업을 수행하면서 침하량을 측정하였는데, 실측침하량은 이론적으로 예측한 침하량보다 현저히 크다는 것을 알게 되었다. 이 논문은 김해점토의 퇴적환경의 관점에서 과다침하가 발생되는 이유를 기술하고 있다.