• Title/Summary/Keyword: 차수벽

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An Experimental Study on the Effect if Fiber Reinforced on CFRD Face Slab Concrere (CFRD 차수벽콘크리트에서의 섬유보강효과에 관한 실험적 연구)

  • 최세진;임정열;김완영;김무한
    • Proceedings of the Korea Concrete Institute Conference
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    • 2000.04a
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    • pp.122-125
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    • 2000
  • CFRD (Concrete Faced Rockfill Dam) face slab concrete has a much capability to occur crack due to drying shrinkage, hydration heat and bas compaction etc. Because of crack of concrete induce structural problem and decrease durability of concrete, it is need to reduce crack of concrete. This is an experimental study to analyze the effect of fiber reinforced on CFRD face slab concrete. for this purpose, it was investigated and analyzed the engineering properties of plain concrete and polypropylene fiber reinforced concrete (PFRC) according to test result ; the test include slump, air content, compressive strength, tensile strength, drying shrinkage and permeability etc. As the results, it was found permeability and drying shrinkage of PFRC less than that of plain concrete.

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Study on Seepage Behavior of Concrete Faced Gravel-Fill Dam (표면차수벽형사력댐의 침투거동에 관한 연구)

  • Cho, Sung-Eun;Kim, Ki-Young;Park, Han-Gyu;Ha, Ik-Soo
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.10a
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    • pp.836-841
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    • 2008
  • CFRD (Concrete Faced Rockfill Dam) has been world-widely constructed due to a lot of advantages compared with rockfill dam and recently, sand/gravel materials, instead of crushed rock materials, are also utilized as a main rockfill material to overcome geological and environmental problems. In this paper, the process of water infiltration into the originally unsaturated sand/gravel-fill dam is studied using two-dimensional saturated-unsaturated seepage theory. According to the results of seepage analysis, if the effective drainage zone is installed in the dam, the reservoir water infiltrate into the dam along a downward flow path towards the lower drainage area. The main body constructed with sand/gravel materials, therefore, remains unsaturated.

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Evaluation of Freezing Rate of Marine Clay by Artificial Ground Freezing Method with Liquid Nitrogen (액화질소를 이용한 인공동결공법 적용시 해성 점토지반의 동결속도 평가)

  • Choi, Hyun-Jun;Lee, Dongseop;Lee, Hyobum;Choi, Hangseok
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.38 no.4
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    • pp.555-565
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    • 2018
  • Nowadays, the artificial ground freezing (AGF) method has been used in many geotechnical engineering applications such as temporary excavation support, underpinning, and groundwater cutoff. The AGF method conducts the freezing process by employing a refrigerant circulating through a set of embedded freezing pipes to form frozen walls serving as an excavation support and cutoff wall. Two refrigerants of brine with the freezing temperature of $-20{\sim}-40^{\circ}C$ and liquid nitrogen with the freezing (evaporating) temperature of $-196^{\circ}C$ are commonly being used in geotechnical applications. This paper performed a series of field experiments to evaluate the freezing rate of marine clay in application of the AGF method. The field experiments consisted of the single freezing-pipe test and the frozen-wall formation test by circulating liquid nitrogen, which is a cryogenic refrigerant, into freezing pipes constructed at a depth of 3.2 m in the ground. The temperature of discharged liquid nitrogen was maintained through the automatic valve, and the temperature change induced by AGF method was measured at the freezing pipes and in the ground with time. According to the experimental results, the single freezing-pipe test consumed about 11.9 tons of liquid nitrogen for 3.5 days to form a cylindrical frozen body with the volume of about $2.12m^3$. In addition, the frozen-wall formation test used about 18 tons of liquid nitrogen for 4.1 days to form a frozen wall with the volume of about $7.04m^3$. The radial freezing rate decreased with increasing the radius of frozen body because the frozen area at a certain depth is proportional to the square of the radius. The radial freezing rate was formulated as a simple equation.

Groundwater Contamination at the Seokdae Waste Landfill Area of Pusan City (부산 석대 폐기물 매립장 일대의 지하수 오염)

  • 정상용
    • Journal of the Korean Society of Groundwater Environment
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    • v.2 no.1
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    • pp.1-8
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    • 1995
  • Wastes produce groundwater contamination, offensive odor, and hazardous gases. This study investigates the contamination of groundwater at the Seokdae waste landfill area and seeks the desirable ways to minimize the groundwater contamination. Groundwater levels, water chemistry and aquifer characteristics of wells were examined around the Seokdae waste landfill. The water chemistry of the Dong stream, the groundwater distribution and flow were also studied. The results of this research show that the estimated quantity of the percolation from the landfill base to the ground is 520 ㎥/day and the extent of groundwater contamination is about 1-1.5 km from the center of the waste landfill. The groundwater contains heavy metals and other toxic elements. The conservation and management of the groundwater of the waste landfill need several monitoring wells to check the quantity and quality of groundwater, pumping wells to extract the contaminated groundwater, and slurry walls to protect the movement of contaminated groundwater.

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A Study on Flexural Rigidity of Two-row Overlap Pile Wall for Deep Excavation Support (대심도 굴착면 지지를 위한 2열 겹침말뚝의 휨 강성에 관한 연구)

  • Choi, Won-Hyuk;La, You-Sung;Kim, Bum-Joo
    • Journal of the Korean Geosynthetics Society
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    • v.17 no.1
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    • pp.33-43
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    • 2018
  • Two-row Overlap Pile wall is a novel retaining wall system with high flexural rigidity and waterproofing for deep excavation support currently being developed in Korea. The Two-row Overlap Pile wall is constructed by making an overlap between consecutive four-axis (or two-axis) auger piles which themselves are overlapped and arranged in zigzag manner. In this study, the flexural rigidity of the Two-row Overlap Pile wall, including the effect of cross-sectional shape, was examined using both theoretical and numerical approaches. The results of investigation suggested that the Two-row Overlap Pile wall formed with two-row piles exhibit greatly higher flexural rigidity than conventional one-row pile walls such as Cast in place pile (CIP) and Secant pile wall (SPW), whereas the effect of overlap length between piles on the flexural rigidity is relatively minimal.

Development of 3-D Flow Model for Porous Media with Scenario-based Ground Excavation (지반굴착 시나리오 기반의 다공성 매질에 대한 3차원 유동해석모델 구축)

  • Cha, Jang-Hwan;Lee, Jae-Young;Kim, Woo-Seok
    • Journal of Korean Society of Disaster and Security
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    • v.10 no.1
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    • pp.19-27
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    • 2017
  • In recent years, ground subsidence has been frequently occurred by underground cavities due to the excessive groundwater inflow, caused by poor construction and management, during tunnel excavation and underground structure construction. In this study, a numerical model (SEEFLOW3D) was developed to estimate groundwater fluctuations for saturated-unsaturated poros media, evaluates the impact on ground excavation with open cut and non-open cut scenarios. In addition, the visual MODFLOW was applied to demonstrate the verification of the model compared with both results. Our results indicated that the RMSE and NRMSE was obtained to range over -3.95~5.7% and 0.56~4.62%, respectively. The developed model was expected to estimate groundwater discharges and apply analysis tool for optimum design of waterproof wall in future.

A Study on the Possibility of Construction Supervision by Geophysical Prospecting (지구 물리탐사에 의한 시공감리성 연구)

  • Shon, Ho-Woong
    • The Journal of Engineering Research
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    • v.2 no.1
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    • pp.165-174
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    • 1997
  • It is not possible to define the earth's interior because of it complicity. However, it can be interpreted directly and/ or indirectly. Geophysics is the subject of this study. To study the possibility of construction supervision by geophysical method, geophysical prospecting was performed and studied at the SamYang pumping well area in Cheju Island, where, although underground dam was constructed, the saline water invade the pumping well area. This study focuses on the construction supervision by electrical measurements. Two electric resistivity survey lines are installed in the pumping well site, and at each line electric survey was conducted at ebb and flow tides. To increase the data quality SP (self-potential) survey was also performed. As a result the geophysical exploration methods explained the defect of construction well, and It shows that geophysical probe can be a useful tool for the construction supervision.

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A Study for Reducing Sea Water Intrusion in the Ground Water Dam Operation (지하댐 운영시 발생하는 염수침입 저감기법에 관한 연구)

  • Yun, Sang-Hoon;Park, Jae-Hyeon;Park, Chang-Kun
    • Journal of Korea Water Resources Association
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    • v.37 no.2
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    • pp.97-108
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    • 2004
  • Recently the ground-water development using the ground-water dam was proposed for the efficient use of the limited water resources especially for islands or seaside area. But in operating the ground-water dam adjacent to seaside an excessive pumping causes the sea-water intrusion which is caused by the drawdown of ground-water level. In this study, the effect of the recharging well method to reduce the sea-water intrusion was evaluated, and was applied to the downstream of the Ssangcheon ground-water dam site. The SUTRA model was used to simulate the salinity transport in the unsaturated and saturated zone. As the results, the effect of recharging method on the downstream of the ground-water dam was proven to be very efficient to reduce the salinity in the pumping well, and especially the best result was shown at the case that the recharging well is located at 40∼60m from the cutoff wall and the recharging rate is up to 6∼7%.

Experiment of Strength of Block Material for Bank Levee Revetment using Eco-friendly Material (친환경 신소재를 이용한 하천 호안용 블록 재료의 강도 실험)

  • Kim, Jong Min;Lee, Du Han;Kim, Won;Kim, Myeong Hwan
    • 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.

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Derivation of Flexural Rigidity Formula for Two-row Overlap Pile Wall (2열 겹침주열말뚝의 휨 강성 산정식 유도)

  • Choi, Wonhyuk;Kim, Bumjoo
    • Journal of the Korean Geosynthetics Society
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    • v.17 no.4
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    • pp.109-118
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    • 2018
  • Two-row overlap pile wall, currently under development for use in deep excavations, is a novel retaining structure designed to perform itself as a cutoff wall as well as a high-stiffness wall by constructing four overlapping piles arranged in zigzag manner at a time using a tetra-axis auger. This wall has a relatively complex cross-section, compared with other types of pile wall, which would make it difficult to determine design parameters related to cross-section. In this study, a flexural rigidity equation has been derived by analyzing both theoretically and statistically various wall cross-sections with different pile diameters and overlap lengths. The flexural rigidity equation was found to show the maximum error rate of 3%.