• Title/Summary/Keyword: 지반고화

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Analysis of Physical and Chemical Properties of CFBC Fly Ash in Vietnam for Solidification (고화재 활용을 위한 베트남 CFBC 플라이애시의 물리적·화학적 특성 분석)

  • Min, Kyongnam;Lee, Jaewon;Lee, Dongwon;Kim, Jinhee;Jung, Chanmuk
    • The Journal of Engineering Geology
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    • v.27 no.3
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    • pp.245-253
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    • 2017
  • Vietnam CFBC fly ash has high CaO content and can be used as a solidification agent for soft ground improvement. However, most fly ash is treated as landfill or waste. In order to utilize fly ash as a solidification agent for soil improvement, the characteristics of fly ash must be accurately determined. In this study, laboratory tests were conducted on fly ash from four CFBC power plants to evaluate the utility of Vietnam fly ash as a solidification agent. As a result of analyzing the physical properties, it was analyzed that all four samples were suitable as material for solidification agent and have suitable particle size for the improvement of soft ground. As a result of analysis of chemical characteristics, it was analyzed that the fly ash of one place could be used as a solidification agent because of the high content of free-CaO. The remaining three fly ash was not suitable for use as a solidification agent due to low Free-CaO content. However, it has a chemical composition similar to that of general fly ash in Korea, so it can be recycled in various ways.

Mechanical Properties of Lean-mixed Cement-treated Soil for Effective Reuse of Dredged Clay (준설점토의 친환경 재활용을 위한 시멘트계 처리토의 장단기 역학거동)

  • Kwon, Youngcheul;Lee, Bongjik
    • Journal of the Korean GEO-environmental Society
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    • v.12 no.9
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    • pp.71-78
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    • 2011
  • Cement treating technique, such as deep mixing method, has been used widely to stabilize the dredged clayey soil for many years. Despite of its effectiveness in treating soil by cement, several efforts have also been made to try to reduce the side effect of the cement that used to stabilize the dredged clay. However, authors considered that more detailed study on the physical and mechanical properties of lean-mixed soil-cement has been required to establish the design procedure to apply the practical problems. Therefore, in this study, the curing time and mixing ratio was used as key parameters to estimate the physical and mechanical properties including long-term behavior. The unconfined strength of lean-mixed soil-cement increase continuously during curing period, 270 days, while increasing rate becomes low in ordinary cement-treated dredged clay. We also concluded that cement-treated dredging clay shows apparent quasi overconsolidation behavior even in low cement proportion. By this study, fundamental approach was carried out for effective reuse of very soft dredged clayey soil both in mechanical and environmental aspect. It can be also expected that this study can propose a basic design data to use the lean-mixed soil cement.

The Optimum Mixture Condition for Stabilization of Songdo Silty Clay (송도 지역 실트질 점성토 고화처리를 위한 최적 배합 조건)

  • Kim, Jun-Young;Jang, Eui-Ryong;Chung, Choong-Ki;Jang, Soon-Ho
    • Journal of the Korean Geotechnical Society
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    • v.27 no.5
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    • pp.5-15
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    • 2011
  • Recent increase of large scale construction near costal area has also increased the application of soft ground treatment. As a result, solidification with cement and lime which increases stability and durability of soils, is frequently used for surface layer stabilization in soft ground site. While stabilization of very soft clay with high plasticity and compressibility has widely been studied, studies on silty clay with low plasticity and compressibility are relatively rare. In this study, after stabilizing low plasticity silty clay of Songdo area with cement and lime under various water contents, mixing ratio, and curing time, uniaxial compression test and plate load test were performed. Strength properties from both tests were considerably consistent. And trackability of construction equipment on the treated surface layer of dredged land was estimated. Finally, optimum mixing condition for Songdo silty clay was proposed.

Strength Characteristics of Solidified Soil with Hardening Agents made of Industrial By-Products (산업부산물을 이용한 지반고화제 혼합토의 강도특성)

  • Kim, Youngsang;Yu, Geunmo;Mun, Kyoungju
    • Journal of the Korean GEO-environmental Society
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    • v.13 no.6
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    • pp.19-26
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    • 2012
  • In this study, geotechnical tests including unconfined compression test were carried out to evaluate the ground improvement effect of the hardening agent, which has been developed by using inter-chemical reactions between slag, fly ash, phosphogypsum and bypass dust on the weathered granite soil and dredged marine clay. Test results show that the strength of weathered granite soil mixed with hardening agent B-2, which uses phosphogypsum as an activator, is higher than that of B-1, which uses bypass dust as an activator. Strengths of B-1 & B-2 hardening agent mixed soil show only 44%~60% of strength of OPC(Ordinary Portland Cement, OPC) mixed soil. However, since B-1 and B-2 agents are made of industrial by-products, they seem economically more effective than ordinary portland cement as well as other present hardening agents. Test results on dredged marine clay show that unconfined compression strength increases with amount of agent and curing days. Unconfined compression strength of 14% B-1 agent mixed soil increases linearly with curing days and reaches only 40% of OPC mixed soil. While unconfined compression strength of 14% B-2 agent mixed soil increases exponentially and reaches 133% of OPC mixed soil. Relationship between deformation modulus and unconfined compression strength of B-1 and B-2 mixed soil can be expressed as $E_{50}=(20{\sim}47)_{qu,28}$, which is similar with lower limit of OPC mixed dredged marine clay.

Strength Characteristics of Improved Dredged Clay for Urgent Recovery of Ground Subsidence (함몰지반 긴급복구를 위한 개량준설점토의 강도 특성)

  • Oh, Sewook;Baek, Seungju;Bang, Seongtaek
    • Journal of the Korean GEO-environmental Society
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    • v.20 no.5
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    • pp.31-38
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    • 2019
  • Recently, there has been an increasing number of ground subsidence (sink-hole) in the downtown areas, and in such a case, it is important to minimize accidents and passages through prompt recovery. With respect to the present recovery method for ground subsidence, the methods of applying the back filling after excavating the ground subsidence or using the grouting injected materials to restore the ground are mostly used, but there has been few studies on materials used for recovering the ground subsidence. Therefore, in order to clarify the characteristics of back filling materials used in the ground subsidence, this study uses the environment-friendly hardening agent to improve the dredged clay, and then, the mixture ratio of hardening agent and mixture ratio of decomposed granite soil is changed to cure for 3, 7, 14 and 28 days to analyze the intensity characteristics of the unconfined compression, and it was compared with the unconfined compression intensity for the previously used cement, a hardening agent. In order to evaluate the characteristics of intensity on the back filling materials, the C.B.R test was carried out, and for the review on whether the back filling materials influence on corrosion of water and sewer pipes and others, the soil non-resistance test was carried out. As a result of the test, for the case of the recovery work of the ground subsidence that requires urgency, it is considered as prudent if the hardening agents of 12% are integrated to cure for 3 days or longer, and for not having the influence on the corrosion of the gas tube or water pipes, it is proposed to mix for 30% or more of the decomposed granite soil. Door model test were conducted To confirm the bearing capacity characteristics of the solidified layer.

Mechanical and Germination Characteristics of Stabilized Dredged Soil (고화준설토의 역학적 특성과 식생 발아 특성)

  • Lee, Miji;Mun, Kyoungju;Yoon, Gillim;Eum, Hyunmi;Kim, Yuntae
    • Journal of the Korean GEO-environmental Society
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    • v.15 no.3
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    • pp.33-40
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    • 2014
  • In this paper, mechanical and germination characteristics of stabilized dredged soils were investigated to recycle dredged soil in eco-friendly manner such as waterfront construction. Non sintering binder (NSB), which was developed by using interchemical reactions between slag, high-calcium fly ash, alkali activator on the dredged marine clay, was added to dredged soil. Ordinary portland cement was also used for the comparison of two binders. Experimental tests such as flow test and unconfined compressive test were carried out to evaluate characteristics of stabilized dredged soil. Leaching test, pH measure, vegetation germination test were also conducted to consider environmental applicability. The unconfined compressive tests shows that unconfined compressive strength (UCS) also increases with the increase of curing time and mixed ratio. UCS of NSB mixtures were higher than those of OPC mixtures. Germination tests showed that germination and sprouting date are better in NSB mixture than OPC mixture. It can be explained that germination decreased as pH and 7-day strength increased.

Environmental Assessment of $Cr^{6+}$ Occurring in Stabilizing Processes of Soft Sea-Bottom using Cement Stabilizers (시멘트 고화제 고결공법에서 발생하는 $Cr^{6+}$의 환경영향 검토)

  • 오영민;김경태
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.14 no.4
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    • pp.319-321
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    • 2002
  • Recently, the injection of cement stabilizer is used as one of ways to improve soft sea-bottom. However, this method makes an argument with $Cr^{6+}$subject to emerge to the seawater from the cement stabilizer. To investigate the amount of$Cr^{6+}$field measurements were carried out in Ochun harbor of Chunsoo Bay. The analysis shows the amount of $Cr^{6+}$in the seawater met the demand of environmental criterion.

A Constitutive Model for Cemented Clay in a Critical State Framework (한계상태이론을 이용한 시멘트 고화처리 점토에 대한 구성 모델)

  • Lee, Song;Lee, Kyu-Hwan;Yi, Chang-Tok;Jung, Dae-Suk
    • Journal of the Korean Geotechnical Society
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    • v.17 no.1
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    • pp.119-129
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    • 2001
  • 연약지반 개량을 위한 시멘트의 사용은 깊은 심도의 점토 지반을 개량하는데 일반적으로 사용되는 기술이 되었다. 시멘트는 지반의 강도를 증가시키고 압축성을 감소시키는 역할을 한다. 시멘트-흙 혼합물의 강도 증가에는 여러 가지 요소가 있는데 이중 대표적인 것은 시멘트량, 흙의 종류, 함수비, 양생시간 등을 들 수 있다. 시멘트 첨가량이 적은 경우, 전단 강도증가는 기본적으로 시멘테이션 효과로 인한 점착력의 증가에 의한 입자들간의 마찰력으로부터 발생한다. 이러한 거동은 과압밀된 흙의 거동과 유사함을 볼 수 있다. 시멘트량이 많은 경우, 강도 증가의 주원인은 입자간의 물리적 결합에 기인하는데 이는 연약한 암석과 비슷한 거동을 한다. 시멘트 고화처리 흙의 응력-변형 거동을 분석하기 위해 한계상태 이론을 적용하였다. 그리고, 토립자간의 시멘테이션 효과를 반영하기 위해 새로운 한계상태 파라메타를 도입하였으며 시멘트 고화처리 점토의 거동을 분석하기 위한 새로운 한계상태 모델을 제시하였다.

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A Study of Relationship Between Engineering and Germination Characteristics of Stabilized Soils with Various Organic Contents (유기질 함량에 따른 고화토의 역학적 특성과 식생발아 특성과의 관계 분석)

  • Yun, Daeho;Kim, Yuntae
    • Journal of the Korean GEO-environmental Society
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    • v.15 no.12
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    • pp.43-51
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    • 2014
  • Organic matter in dredged soil has a lot of engineering problem in ground including a large settlement, crack propagation, low bearing capacity and low friction angle. From an agricultural point of view, however, organic matter contributes greatly soil quality and plant health. This paper investigated the relationship between engineering and germination characteristics of stabilized mixture consisting of different ratios of organic content (0 %, 10 %, 20 %, 30 %) for recycling dredged soil including organic matter. Several series of laboratory tests such as flow test, unconfined compressive test and consolidation test were performed to find out engineering characteristics. pH, percent of germination and growth of plants were also measured to investigate the germination characteristics. The experimental results indicated that, as organic content increased, unconfined compressive stress decreased and compression and swelling indices increased. However, percent of germination and plant growth increases as organic content increases.