• Title/Summary/Keyword: Aggregate pier

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A Study on the Characteristics of Bearing Capacity for Rammed Aggregate Pier in Sand (사질토지반에서 짧은 쇄석다짐말뚝의 배치형태에 따른 지지력특성에 관한 연구)

  • Chun, Byung-Sik;Kim, Young-Hun;Yoo, Woo-Hyun;Kim, Jong-Hwan
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.03a
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    • pp.195-198
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    • 2009
  • Rammed Aggregate Pier method is intermediate foundation of deep and shallow foundation, it has been built on world wide. But the investigation and research in domestic is not accomplished. In this paper, examined details of different spacing of piles, bearing capacities, respectively, conclude with recommendations on how RAP can be used in future needs. This documentation further provides comparisons of the laboratory test results which were obtained from differenciate the spacing of piles, namely installed rammed aggregate pier. Strain control test was conducted to determine the bearing capacities of the piers; 20mm, 30mm and 40mm diameter drilling equipment to drill holes were installed in sand at initial relative densities of 40%. By comparing different spacing of piles, in this experiment, piles are spaced structually span, form a ring shape, narrowing the distance of each other, to the center. the result shows that as diameter of pier is bigger in diameter, bearing capacity also dramatically increased due to raised stiffness. Also, the space between each piers narrowed, settlement rate of soil was decreased significantly. From the test results, as the space between each piles were getting closer, allows greater chances to have resistance to deformation, shows improved stability of structures.

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A Study on the Bearing Capacity of Rammed Aggregate Pier as the Intermediate Foundations (중간기초개념으로서 짧은 쇄석다짐말뚝의 지지력 특성에 관한 연구)

  • CHUN BYUNG-SIK;KIM KYUNG-MIN;KIM JUN-HO
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2004.11a
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    • pp.247-252
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    • 2004
  • To secure stability and availability of Rammed Aggregate Pier method as the foundation of a structure, the bearing capacity and failure behavior characteristics was studied through soil laboratory tests in a model ground. In this study, soil laboratory tests use carried out to find the applicability of RAP method as the foundation of a structure. And bearing capacity and the failure mechanism of RAP method was studied according to relative density($60\%,\;70\%,\;90\%$), diameter(45mm, 60mm, 70mm) of each pier ana depth(5cm, l0cm, 15cm, 20cm, 25cm, 30cm). Earth pressure cell is set up approach RAP and 1.0D space at RAP center. Bearing acpacity and the failure mechanism of RAP is investigated by load test As a result, bulging failure was happened in $5\~10cm\;(1.0D\~2.00)$ depth which the maximum lateral earth pressure is acting. Especially, diameter changing of RAP are in inverse proportion to the relative density and the lateral stress is very much influenced by the lateral earth pressure in every layer and tends to decrease according to depth.

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Application of Rammed Aggregate Pier(Geopier) for Foundation Reinforcement of Structures (구조물 기초보강용 짧은 쇄석다짐말뚝(Geopier)의 적용성 및 활용방안에 관한 연구)

  • Joeng, Gyong-Hwan;Jung, Sun-Tae;Moon, Jun-Bai;Kim, Dong-Jun;Baek, Kyung-Jong
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.10a
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    • pp.479-488
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    • 2005
  • Geopier soil reinforcement system which crushed aggregate is put into a hole and rammed the aggregate with tamper is a viable alternative to deep foundation to over-excavation and replacement. Also, Geopier is intermediate foundation of deep and shallow foundation. In this paper, the value of Geopier element stiffness modulus($K_g$) when designed is compared with the measured value($K_g$) by the in-situ modulus Load test in the field. Also, this paper presents a technology overview of system capabilities and application for foundation reinforcement of structures.

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The Characteristics of Various Stress in Cohesionless Soil with the Rammed Aggregate Pier (짧은 쇄석다짐말뚝(RAP)이 설치된 사질토지반의 응력변화 특성)

  • Chun, Byung-Sik;Kim, Kyung-Min;Kim, Jun-Ho
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.1108-1117
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    • 2005
  • RAP(rammed aggregate pier) method which is intermediate foundation of deep and shallow foundation is used to improve the ground with high compaction energy. This method is widely spread around the world, but there are few examples and systemic researches for failure mechanism and bearing capacity of this method are not organized yet. In this paper, soil laboratory tests were carried out to evaluate the applicability of RAP method as the foundation of a structure. And the bearing capacity and the failure mechanism of RAP method were studied with respect to various relative densities(35%, 65%, 90%), diameters(45mm, 60mm) and lengths(20cm, 30cm, 40cm). As results, stress concentration ratio decreased as diameter of RAP was increasing or length of RAP was decreased or relative density was decreased. however these results were not always constant. because systematic interaction between relative density and diameter and length of RAP can affect stress concentration ratio, more studies on stress concentration ratio are needed throughout laboratory and field tests.

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A Study on Bearing Capacity for Installed Rammed Aggregate Pier (RAP의 배치형태에 따른 지지력에 관한 연구)

  • Kim, Younghun;Cho, Changkoo;Chun, Byungsik
    • Journal of the Korean GEO-environmental Society
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    • v.10 no.5
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    • pp.19-26
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    • 2009
  • Rammed Aggregate Pier (RAP) method is intermediate foundation between deep and shallow foundation, and it has been built in world wide. RAP represents a relatively new method that has grown steadily over 19 years since Geopier of USA developed this revolutionary method in 1989. The investigation and research in domestic is not accomplished. In this paper, the examined details of different spacing of piles, bearing capacities, respectively, conclude with recommendations on how RAP can be used in future needs. This documentation further provides comparisons of the laboratory test results which were obtained from changing the spacing of piles, namely installed rammed aggregate pier. Laboratory model test was administered in a sand box. Strain control test was conducted to determine the bearing capacities of the piers; 20 mm, 30 mm and 40 mm RAP in diameter using drilling equipment to make holes were installed in sand at initial relative densities of 40%. By comparing different spacing of piles, in this experiment, piles are spaced structually span, form a ring shape, narrowing the distance of each other, to the center. the result shows that as diameter of pier is bigger in diameter, bearing capacity also dramatically increased due to raised stiffness. Also, as the space between each piers was closed, the settlement rate of soil was decreased significantly. From the test results, as the space between each piles were getting closer, it allows greater chances to have more resistance to deformation, and shows more improved stability of structures. After from the verification work which is continuous leads the accumulation of the site measuring data which is various, and bearing capacity and the settlement is a plan where the research will be advanced for optimum installed RAP.

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A Study on the Shear Strength Characteristics of Composited Ground applying RAP Method by Large Direct Shear Test (대형직접전단시험에 의한 RAP 복합지반의 전단강도 특성 연구)

  • Chun, Byung-Sik;Seo, Deok-Dong;Kim, Jong-San
    • Proceedings of the Korean Geotechical Society Conference
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    • 2004.03b
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    • pp.82-89
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    • 2004
  • To secure stability and availability of Rammed Aggregate Pier method as the foundation of a structure, the shear strength characteristics according to the area replacement ratio of RAP and the relative density of in-situ ground was studied through soil laboratory tests and large direct shear tests in a model ground. As a result, the internal friction angle tends to increase in proportion to in-situ relative density(Very Loose, Loose, Medium) in composite ground formed by the same area replacement ratio of RAP and also increase in proportion to increasing the area replacement ratio(30, 40, 50%) of RAP in the same ground condition. Furthermore, the comparative analysis between the experimental value and theoretical value of the shear strength is carried out.

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Estimation of Resistance Bias Factors for the Ultimate Limit State of Aggregate Pier Reinforced Soil (쇄석다짐말뚝으로 개량된 지반의 극한한계상태에 대한 저항편향계수 산정)

  • Bong, Tae-Ho;Kim, Byoung-Il;Kim, Sung-Ryul
    • Journal of the Korean Geotechnical Society
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    • v.35 no.6
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    • pp.17-26
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    • 2019
  • In this study, the statistical characteristics of the resistance bias factors were analyzed using a high-quality field load test database, and the total resistance bias factors were estimated considering the soil uncertainty and construction errors for the application of the limit state design of aggregate pier foundation. The MLR model by Bong and Kim (2017), which has a higher prediction performance than the previous models was used for estimating the resistance bias factors, and its suitability was evaluated. The chi-square goodness of fit test was performed to estimate the probability distribution of the resistance bias factors, and the normal distribution was found to be most suitable. The total variability in the nominal resistance was estimated including the uncertainty of undrained shear strength and construction errors that can occur during the aggregate pier construction. Finally, the probability distribution of the total resistance bias factors is shown to follow a log-normal distribution. The parameters of the probability distribution according to the coefficient of variation of total resistance bias factors were estimated by Monte Carlo simulation, and their regression equations were proposed for simple application.

Constructing Database and Probabilistic Analysis for Ultimate Bearing Capacity of Aggregate Pier (쇄석다짐말뚝의 극한지지력 데이터베이스 구축 및 통계학적 분석)

  • Park, Joon-Mo;Kim, Bum-Joo;Jang, Yeon-Soo
    • Journal of the Korean Geotechnical Society
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    • v.30 no.8
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    • pp.25-37
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    • 2014
  • In load and resistance factor design (LRFD) method, resistance factors are typically calibrated using resistance bias factors obtained from either only the data within ${\pm}2{\sigma}$ or the data except the tail values of an assumed probability distribution to increase the reliability of the database. However, the data selection approach has a shortcoming that any low-quality data inadvertently included in the database may not be removed. In this study, a data quality evaluation method, developed based on the quality of static load test results, the engineering characteristics of in-situ soil, and the dimension of aggregate piers, is proposed for use in constructing database. For the evaluation of the method, a total 65 static load test results collected from various literatures, including static load test reports, were analyzed. Depending on the quality of the database, the comparison between bias factors, coefficients of variation, and resistance factors showed that uncertainty in estimating bias factors can be reduced by using the proposed data quality evaluation method when constructing database.

Field Evaluation of Scour Countermeasure Using Geobag (지오백 세굴보호공법의 현장 적용성 평가)

  • Park, Jae-Hyun;Kwak, Ki-Seok;Lee, Ju-Hyung;Chung, Moon-Kyung
    • Proceedings of the Korean Geotechical Society Conference
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    • 2006.03a
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    • pp.1251-1258
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    • 2006
  • Field evaluation of new scour countermeasure using geobag and aggregate is performed to prepare for the basis of design and construction standard in Korea. Polyester non-woven geotextile is determined as a geobag material and tire cord is used to sew up the geobag which contain aggregate. Hwasang-gyo(bridge) is selected as a pilot test site through office review and field investigation. According to the design flood of Hwasang-gyo(bridge), the size and volume of geobag are calculated and construction area and required number of geobags are computed by considering the specification of the pier and foundation of the bridge. After construction, scour depth around geobag construction area is measured and the stability of geobag is ascertained by using pole and digital camera.

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An Experimental Study on the Bearing Capacity and Failure Behavior of Composite Ground Reinforced by RAP Method (RAP 복합지반의 지지력 및 파괴거동에 관한 실험적 연구)

  • 천병식
    • Journal of the Korean Geotechnical Society
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    • v.20 no.5
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    • pp.127-134
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    • 2004
  • Rammed Aggregate Pier (RAP) has extensive applicability as for a foundation of structures. In this study, bearing capacity of the reinforced ground by RAP and the failure behavior of RAP are investigated through experiments. RAPs with diameters of 45, 60, 70 mm were installed in sand, of which relative densities are 60, 70, 90%. Then, two columns of pressure gauges, near the RAPs and one diameter off from the center of piers, are installed 5, 10, 15, 20, 25, 30 cm from the surface of the ground. The test results show that maximum lateral earth pressure is observed near 5∼10 cm (1.0∼2.0D) from the surface, which indicates the occurrence of bulging failure type. In addition, deformation of RAP in radial direction increases with lower relative density of the ground. Furthermore, lateral stress distribution decreases with depth.