• Geomechanics and Engineering
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• 제35권5호
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• pp.511-523
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• 2023

Canal-side roads frequently collapse due to an unexpectedly greater soft-clay thickness with a rapid drawdown situation. This causes annually increased repair and reconstruction costs. This paper aims to explore the effect of soft-clay thickness on the failure in the canal-side road in the case study of Phra Nakhon Si Ayutthaya rural road no. 1043 (AY. 1043). Before the actual construction, a field vane shear test was performed to determine the undrained shear strength and identify the thickness of the soft clay at the AY. 1043 area. After establishing the usability of AY. 1043, the resistivity survey method was used to evaluate the thickness of the soft clay layer at the failure zone. The screw driving sounding test was used to evaluate the undrained shear strength for the road structure with a medium-stiff clay layer at the failure zone for applying to the numerical model. This model was simulated to confirm the effect of soft-clay thickness on the failure of the canal-side road. The monitoring and testing results showed the tendency of rapid drawdown failure when the canal-side road was located on > 9 m thick of soft clay with a sensitivity > 4.5. The result indicates that the combination of resistivity survey and field vane shear test can be successfully used to inspect the soft-clay thickness and sensitivity before construction. The preliminary design for preventing failure or improving the stability of the canal-side road should be considered before construction under the critical thickness and sensitivity values of the soft clay.

• Current Research on Agriculture and Life Sciences
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• 제2권
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• pp.98-108
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• 1984

Generally, in case of constructing the embankments on the soft clay layers, one-dimensional consolidation settlement under the assumption of a middle position stress in a single layer makes a great difference with the integral value, ie. the final settlement. Consequently, to find how many equal segments of the soft clay layer are needed to converge into the integral value and which position should be taken as a position of mean stress, authors compared the theoretical value of the settlement due to one-dimensional consolidation with the practical value of the settlement due to two dimensional consolidation. The obtained results are as follows. 1) The practical value of the two-dimensional consolidation settlement can be estimated by the 74-83% theoretical value of the one-dimensional consolidation settlement. 2) When the soft clay layer was cut into 8-16 equal segments according to the depth, one-dimensional consolidation settlement converge into the integral value. 3) Assuming a total soft clay layer as a single one, the depth of a mean stress position is 0.29-0.37 of the thickness of the total soft clay layer. 4) The Hyperbola Method which presumes the long-term settlement from the short-term practical value of settlement is credible, because all practical value of the settlement are in safe side of the standard error of estimation and the correlation coefficient is up to 0.95.

• 한국안전학회지
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• 제16권1호
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• pp.53-58
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• 2001

Constructions on the soft clay layer of low strength and high compression bring out many problems. Recent studies show that strength of the soft clay layer could be substantially improved by mixing quicklime. For the purpose, a series of uniaxial compression tests were performed, using quicklime, in order to analyze strength characteristics. The major test results are summarized following : When water content is 90%, the strength is observed to precipitously increase between 3～14 days, then, the extent slowly increase in relative terms. When water content is 130%, the strength is observed to precipitously increase up to 28 days. When the strength of water content 90% is compared to that of water content 130%, the initial strength of the former is higher than that of the latter. The analyses show that the improvement of soft clay layers can be realized by the mixture of both quicklime and sand, and by the mixture of quicklime only.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.731-738
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• 2002

Recently, as large constructions on the coast are performed frequently, surface layer stabilization method which Is one of the improvement methods for dredged soft clay has been applied. However, there have been few studies about the surface layer stabilization method. The purpose of this study is to clarify characteristics of ultra-soft marine clay and hardening agent. Also, optimal mixture ratio of hardening agent was verified through the laboratory tests such as statistical analysis and pilot tests. Laboratory tests were performed with proper hardening agent and test soil and standard mixing tables of hardening agent were determined according to ground conditions through statistical analysis. Also, applicability of surface layer stabilization method to field was verified by pilot tests. From the results of the tests, it was found that hardening agent materials such as cement, slag, fly-ash, inorganic salts, arwin, gypsum etc. affect on the appearing compressive strength. It was defined optimal mixture ratio which satisfies the required compressive strength from the statistical analysis. Also, It was compared the effect of ground improvement by cements and hardening agents through the pilot tests. This study will serve as data for design or construction criteria of stabilization of surface layer on ultra-soft marine clay.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2007년 가을학술발표회
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• pp.3-38
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• 2007

The depositional characteristics of Busan clay are initially described in this paper. The deposits of the Nakdong River estuary are composed of some different layers, which have been affected by marine transgression and regression. The upper clay layer is thick and soft. The lower clay layer and some depth of the upper clay layer have been leached by artesian pressure existing in an aquifer below. The clay shows unique physical and engineering characteristics due to leaching. Several large-scale reclamation projects have been performed in this delta area. The preloading method using long vertical drains has been applied for soft ground improvement. Experiences obtained from ground improvement are mentioned in connection with the depositional characteristics of the clay layers.

• 한국지반환경공학회 논문집
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• 제25권4호
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• pp.5-12
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• 2024

간석지(공유수면) 내 단지를 조성하는 경우, 해안 퇴적지반 특성상 대규모 성토재가 필요하고, 단지공사 시 불가피하게 발생되는 연약점성토를 성토재료로 활용하는 것이 자원재활용 및 경제적 측면(소요토량감소)에서 필요한 실정이다. 본 연구에서는 연약점성토의 성토재활용에 따른 절취교란된 점성토의 압밀특성변화를 파악하고, 압밀침하량 설계방안에 대하여 제안하였다. 연구 대상지의 압밀시험결과를 통해 교란(절취)에 따른 압밀특성치 변화(압축지수감소, 선행하중산정불가)를 확인하였고, 점성토 성토층을 복합대상층(압밀대상 및 상재하중층)으로 산정(압밀침하량)하는 방안이 실제거동과 부합한 결과로 분석되었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.499-506
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• 2004

The use of dredged soft marine clay is increasing due to a shortage of coarse material available. This paper presents a stabilization method that can increase shear strength of the surface layer of a dredged clay deposit at dates much earlier than usual. The desiccation of the upper soft 1-2m layer can be accelerated by interrupting water seeping from its bottom with impervious geotextile. Just below the geotextile, enough pervious material is provided so that the underlying deposit can be drained through it. This scheme is proved to be effective through theoretical analysis.

• 한국지반환경공학회 논문집
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• 제9권1호
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• pp.41-46
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• 2008

본 연구에서는 대심도 연약지반에서 PHC말뚝을 항타관입한 후 일정기간 이후 정재하시험을 통한 하중전이분석을 실시하였다. 하중전이분석에서 단위주면마찰력은 상부의 사질토에서 $7.4t/m^2$, 심도 14m에서 33m의 점성토구간에서는 $6.4t/m^2$, 말뚝선단부가 근입된 사질토에서는 $23.3t/m^2$이 발휘되었으며, 단위선단지지력은 $955t/m^2$으로 실측되었다. 전이된 단위주면마찰력과 국내외에서 알려져 있는 정역학적 지지력산정식과의 비교를 해본 결과 토층별로 가장 적합한 공식을 선정한다면, 사질토의 단위주면마찰력의 경우 한국지반공학회의 구조물기초설계기준 및 해설이, 점성토의 단위주면마찰력의 경우 철도청의 철도설계기준이 가장 실측치에 근접한 값을 나타내었다.

• 한국지반공학회논문집
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• 제35권11호
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• pp.15-23
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• 2019

본 연구에서는 수치해석을 이용해 격벽형 중력식 2열 합성소일벽(BSCW) 공법의 변위에 대해 분석하고 고찰하였다. 수치해석 모델은 BSCW 앞면 중심부의 현장 변위 데이터를 통하여 검증되었고 세 가지 다른 점토지반(soft, medium, stiff)의 점착력 및 탄성계수에 대한 매개변수 해석을 수행하였다. 또한 Jumbo Special Pattern 공법을 이용한 저면 시멘트 칼럼의 Center-To-Center 간격에 대한 매개변수 해석도 수행하였다. 매개변수 해석 결과, BSCW의 변위는 연약 점토 지반에서 가장 크게 나타났고, 낮은 탄성계수를 가진 지반인 경우 낮은 Center-to-Center 간격이 요구되었다.

• 한국해양공학회지
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• 제10권4호
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• pp.141-148
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• 1996

Use of stone column for deep ground treatment in soft clay soils is an effective method. The stone column significantly increases load carrying capacity of the soft clay soil. A analysis method for bearing capacity of stone column in soft clay soil is developed. The capacity made by developed method are compared wity observed values from field load test and a reasonable correlation is noted.