• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.477-477
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• 2018

하천의 제방은 하천수의 범람을 방지하기 위하여 인공적으로 만든 구조물로서, 유수의 흐름을 일정하게 하고 자연재해에 대하여 제내지를 보고하기 위한 목적도 있다. 제방은 제내지와 제외지의 수위차로 인해 발생하는 파이핑, 제방의 월류, 사면의 탈락 등으로 파괴가 발생되고, 제방의 파괴는 제내지의 인명, 토지, 건물 등에 많은 피해가 발생한다. 이러한 제방의 파괴를 방지하기 위하여 제방 사면의 호안, 차수벽, 수제 등을 설치하고 있으며, 구조물 외에도 제방 응급복구를 위한 모래주머니, 비탈면 보호 시설 등을 이용한 피해방지에 대한 대책을 세우고 있다. 제방 구조물의 대부분은 콘크리트를 이용한 고강도 재료를 사용하여 설치되고 있으며, 재료의 환경성에 대한 문제점이 대두되어 왔다. 이에 따라 코코넛껍질을 이용한 사면 보호공, 고강도 식생매트를 이용한 사면 보호 등 친환경 재료를 이용한 사면보호 공법에 대한 연구들이 다양하게 진행되어 왔다. 본 연구에서는 미생물을 이용하여 사면을 보호하기 위한 블록 및 피복기법에 대한 연구를 진행하고 있으며, 다양한 환경성 및 무독성 검증도 병행중에 있다. 그 중 본 연구에서는 신소재와 황토, 모래, 석고를 다양한 비율로 조합하여 블록으로 활용하기 위한 일축압축 강도 실험을 수행하였으며, 신소재의 소류력 저항능력을 실험하기 위하여 안동 하천실증연구센터의 급경사 수로에 신소재를 피복한 시험구를 조성하고 5m/s 이상의 유속에서 저항능력 실험을 수행하였다. 본 연구에서는 본 실험 결과를 기반으로 하여 추후 다양한 친환경 재료를 이용한 조합을 통해 기존 콘크리트 블록에 준하는 강도를 발현할 수 있는 신소재 블록의 개발을 목표로 하고 있다.

• Journal of the Korean GEO-environmental Society
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• v.6 no.4
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• pp.65-71
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• 2005

Recently, difficulties in soft ground improvement that caused by effectiveness of the ground improvement, the durability and environmentally friendliness of the injection material come to the fore. This paper studies the field applicability of the SCM in reinforcement and seepage cutoff of the back of an existing continuous wall. SCM uses double rod which imposes heavy pressure($10-100kgf/cm^2$) to disturbed, cut, discharge, and mix the ground. It is observed that a bulb is formed by using cement paste and environmentally friendly injection materials with minimal alkali leaching. Unconfined compression test and fish poison tests are performed. Test results indicate that the method results in higher durability, less leaching through use of the environmentally friendly injection material, and faster mobilization of the strength. In addition, field tests confirm the formation of the bulb and the seepage cutoff wall.

• Journal of the Korean Geotechnical Society
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• v.23 no.7
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• pp.99-104
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• 2007

The deep soil mixing, on ground modification technique, has been used for many diverse applications including building and bridge foundations, port and harbor foundations, retaining structures, liquefaction mitigation, temporary support of excavation and water control. This method has the basic objective of finding the most efficient and economical method for mixing cement with soil to secure settlements through improvement of stability on soft ground. In this research, the experiments were conducted on a laboratory scale with the various test conditions of mixing method; the angle of mixing wing, mixing speed. Strength and shapes of improved soil of these test conditions of deep mixing method were analysed. From the study, it was found that the mixing conditions affect remarkably to the strength and shapes of improved soils.

• Journal of Soil and Groundwater Environment
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• v.6 no.3
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• pp.53-59
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• 2001

There is a lot of method to manage the insanitary landfill but vertical cutoff walls have been widespreadly used and were installed into the subsurface to act as a barrier to horizontal groundwater flow, The stabilized material such as specialized cement or mixed soil with additives has been generally applied for the materials of the deep soil mixing barrier in korea. The amount of the stabilized material is dependent on the field conditions, because the mixing ratio of the material and the field soil should achieve a requirement in the coefficient of permeability, lower than 1.0$\times$$10^{7}$cm/sec. This study determined the quantity and optimized function ratio of the stabilized material in the formation process of the mixed barrier that was added with stabilized material on the field soil classified into SW-SC under USCS (Unified Soil Classification System). After that the fly ash and lime were selected as an additives an that could improve the function of the stabilized material and then the method to improve the functional progress in the usage of putting into the stabilized material as an appropriate ratio was studied and reviewed. The author used the flexible-wall permeameter for measuring the permeability and unconfined compressive strength tester for compressive strength, and in the view of environmental engineering the absorption test of heavy metals and leaching test regulated by Korean Waste Management Act were performed. As the results, the suitable mixing ratio of the stabilized material in the deep soil mixing barrier was determined as 13 percent. To make workability easy, the ratio of stabilized material and water was proven to be 1 : 1.5. With the results, the range of the portion of the additives(fly ash : lime= 70 : 30) was proven to be 20-40% for improving the function of the stabilized material, lowering of permeability. In heavy metal absorption assessment of the mixing barrier system with the additives, the result of heavy metal absorption was proved to be almost same with the case of the original stabilized material; high removal efficiency of heavy metals. In addition, the leaching concentration of heavy metals from the leaching test for the environmental hazard assessment showed lower than the regulated criteria.

• Journal of the Korean Geotechnical Society
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• v.21 no.1
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• pp.43-50
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• 2005

Jet grouting method is widely being used in many geotechnical problems, especially for the purpose of reinforcement of clayey ground and cut-off wall of sandy ground. However, its design depends on highly empirical method, in which many researches have been undertaken. This study investigated the effect of cavitation on jet grouting. Small-scaled model tests were carried out using specially designed and fabricated device to analyze the effect of cavitation on jet grouting with various test conditions including ground condition, injection pressure, and injection time. The test results show that cavitation has a significant effect on jet grouting, and it has a potential for engineering application.

• Journal of the Korean GEO-environmental Society
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• v.22 no.6
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• pp.27-32
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• 2021

Due to heavy rainfall and typhoons caused by climate change, it has become common to witness heavy rain that exceeds the design frequency of agricultural reservoirs. This has brought greater attention to the safety of irrigation facilities including agricultural reservoirs. Out of approximately 17,740 reservoirs available in Korea, 83.87% were built before 1970. To ensure the safety of these old reservoirs, their embankments are being repaired and reinforced using various techniques. Among these techniques, using the cement-bentonite cutoff wall makes it possible to construct diaphragm walls with slurry composed of cement and bentonite, while excavation. The advantages of this technique include that it is simple and fast, and ensures the uniformity of cutoff walls by enabling the immediate application of the replacement method to excavation areas; thus excellent performance is guaranteed. However, despite these advantages, the technique is not commonly used in Korea. Thus, this study investigated the changes in strength and permeability by varying the mix ratio of cement and bentonite. As a major experimental results, when the cement of 200 kg/m³ and the bentonite of 60 to 80 kg/m³ is most suitable for the repair and reinforcement of the reservoir embankments.

• Journal of the Korea Concrete Institute
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• v.27 no.4
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• pp.419-426
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• 2015

The purpose of this study is to investigate experimentally the optimum mix design and site application case of soil mixing wall (SMW) method which is cost-effective technique for construction of walls for cutoff wall and excavation support as well as for ground improvement before constructing LNG storage tank typed under-ground. Considering native soil condition in site, main materials are selected ordinary portland cement, bentonite as a binder slurry and also it is applied $1,833kg/m^3$ as an unit volume weight of native soil, Variations for soil mixing wall are as followings ; (1) water-cement ratio 4cases (2) mixing velocity (rpm) 3levels (3) bleeding capacity and ratio, compressive strength in laboratory and site application test. As test results, bleeding capacity and ratio are decreased in case of decreasing water-cement ratio and increasing mixing velocity. Required compressive strength (1.5 MPa) considering safety factors in site is satisfied with the range of water-cement ratio 150% below, and test results of core strength are higher than those of specimen strength in the range of 8~23% by actual application of element members including outside and inside in site construction work. Therefore, optimum mix design of soil mixing wall is proposed in the range of unit cement $280kg/m^3$, unit bentonite $10kg/m^3$, water-cement ratio 150% and mixing velocity 90rpm and test results of site application case are satisfied with the required properties.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.1
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• pp.31-48
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• 2019

The artificial ground freezing (AGF) method is a groundwater cutoff and/or ground reinforcement method suitable for constructing underground structures in soft ground and urban areas. The AGF method conducts a freezing process by employing a refrigerant circulating through a set of embedded freezing pipes to form frozen walls serving as excavation supports and/or cutoff walls. However, thermal expansion of the pore water during freezing may cause excessive deformation of the ground. On the other hand, as the frozen soil is thawed after completion of the construction, mechanical characteristics of the thawed soil are changed due to the plastic deformation of the ground and the rearrangement of soil fabric. This paper performed a field experiment to evaluate the freezing rate of marine clay in the application of the AGF method. The field experiment was carried out by circulating liquid nitrogen, which is a cryogenic refrigerant, through one freezing pipe installed at a depth of 3.2 m in the ground. Also, a piezo-cone penetration test (CPTu) and a lateral load test (LLT) were performed on the marine clay before and after application of the AGF method to evaluate a change in strength and stiffness of it, which was induced by freezing-thawing. The experimental results indicate that about 11.9 tons of liquid nitrogen were consumed for 3.5 days to form a cylindrical frozen body with a volume of about $2.12m^3$. In addition, the strength and stiffness of the ground were reduced by 48.5% and 22.7%, respectively, after a freezing-thawing cycle.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.1
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• pp.145-151
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• 1991

The final purpose of this study is to examine the uses of coal ash, by-product from thermal power plant as a type of filling-embankment materials and the reuses of ash ponds. In this time, to investigate the dynamic properties, we made the test piece specimen with coal ashes, and obtained the damping ratio. In place(ash pond), the damping property by underground wall was investigated before and after soil improvements. The damping ratio of coal ash test piece specimen of 12% cement is the highest and that of 9% cement or chemical grout, that of 6% cement is in order. In same coal ash test piece, the damping ratio increases with decreasing the void ratio. In conclusion, it could be said that the damping ratio increases with the stiffness of materials. In the ash pond, the damping effect is the most when trench is set through the vibration wave propagation course, and when soil is improved the higher stiffness of the improved soil is, the more damping effect appeared. It is justified to obtain not only the dropping of permeability and the strength increase, but also the damping effect fairly by soil improvements.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.419-419
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• 2011

이상호우, 사막화, 빙하융해, 생태계 먹이사슬 변화, 이상기온 등 기후변화의 행태는 지구 곳곳에서 다양하게 발발되고 있으며 그로인해 발생되는 인적 물적 피해가 심각하다. 1996년 집중호우에 의한 연천댐체 파괴, 2002년 8월의 낙동강 유역 장기홍수, 2002년 태풍 루사 및 2003년 태풍 매미 등 국내에서는 기후변화 중에서도 주로 이상호우로 인해 발생하는 피해가 많았으며 이들은 주기성이나 특성을 갖지 않아 예측이 어려운 관계로 망양보뢰 식의 후처리에 급급한 실정이었다. 최근 기후변화에 따른 지역별 홍수량, 가뭄량 등에 관한 연구가 가속화되고 있으며, 이와 더불어 해당 기후모델 발현 시 기존 구조물에 미치는 영향에 대한 연구도 필수적이다. 나아가 기존 구조물 뿐 아니라 새로 시공되는 구조물의 설계에서 기후변화에 대한 안정성을 위해 추가적으로 포함해야 할 요소가 있는지에 대한 연구도 필요하다. 본 연구에서는 가상 기후모델에 대해 그 모델이 예측하는 홍수량이 실제 발현되었을 경우를 가정하여, 기존 수공구조물의 안정성에 미치는 영향을 살펴보고 영향인자의 민감도를 분석하고자 한다. 대상 수공구조물은 붕괴 시 영향력이 큰 정도를 기준으로 필댐, 콘크리트차수벽형석괴댐(CFRD), 콘크리트중력식댐, 제방으로 그 범주를 제한 하였으며 대상유역은 한강으로 가정하였다. 구조물의 안정성 검토방법은 각 구조물의 종류에 따라 상이하다. 흙이 주 재료인 제방과 필댐의 경우, 침투(Piping)와 비탈면(Sliding)에 대한 안정성 평가가 이루어지며 CFRD는 댐체와 벽체로 나누어 안정성평가를 하며 댐체 안정성 평가방법은 필댐과 유사하다. 본 연구에서는 하천설계기준(2009)과 댐설계기준(2005)에 따라 각 구조물의 기준안전율을 책정하였으며 점착력, 내부마찰각, 단위중량 등의 물성치는 해당 지역의 토질특성에 따라 여러 문헌을 참고하여 설정하였고 이를 SEEP/W, SLOPE/W 프로그램을 이용하여 구조해석을 실시하였다. 콘크리트중력식댐은 활동, 전도, 지지력에 대해 각각 안정성을 평가하며 MIDAS와 ABAQUS 프로그램을 병행하여 해석하였다. 민감도(Sensitivity)란 안정성에 영향을 미치는 설계인자들의 변화에 따라 안정성이 어떻게 변화하는 지를 말한다. 기후변화에 의한 수공구조물 설계인자 민감도 연구를 통해 기존 설계과정 또는 안정성 검토 시 해당인자의 기여도를 높이거나 새로운 설계인자를 추가하여 미래 상황에 대한 구조물의 위험 정도를 과거대비 상세히 예측할 수 있으며 나아가 적절한 대응 방안 제시에 기여하여 기후변화에 따른 피해를 감소할 수 있을 것이라고 생각된다.