• Title/Summary/Keyword: Base expansion type micropile

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Evaluation of the Installation Mechanism of the Micropile with the Base Expansion Structure Using a Centrifuge Model Test (원심모형실험을 활용한 선단확장형 마이크로파일의 설치 메커니즘 평가)

  • Kim, Jae-Hyun;Kim, Seok-Jung;Han, Jin-Tae;Lee, Seokhyung
    • Journal of the Korean Geotechnical Society
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    • v.37 no.11
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    • pp.37-49
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    • 2021
  • Micropiles are widely used in construction field to enhance bearing capacity and reduce settlement of existing foundation. It has various benefits such as low construction expense, simple installation process, and small construction equipment. Recently, new microple equipped with the base expansion structure at the end has been developed to improve the foundation bearing capacity. The improvement of load capacity can be conceptually achieved by expanding the base expansion structure when a load is applied to the micropile. However, the expansion mechanism of the base expansion structure and the improvement of load capacity of the micropile were not yet experimentally validated. Therefore, in this study, a series of centrifuge model tests was performed to evaluate the effect of the base expansion structure on the improvement of load capacity. Two types of soil, sand and weathered rock, were prepared and the loading tests were performed using the real micropile with the base expansion structure. During the tests, the earth pressures surrounding the base expansion structure were monitored. As a result, when a load of 30 kN was applied to the micropile, the increase in the ratio of the horizontal to vertical pressure increment (∆σh/∆σ𝜈) ranged from 0.4 to 0.58 in sand and ∆σh/∆σ𝜈 = 0.19 in weathered rock, respectively. Therefore, it can be concluded that the increase in the horizontal earth pressure adjacent to the base expansion structure will improve the bearing capacity of the micropile.

Three-Dimensional Numerical Analysis for Verifying Behavioral Mechanism and Bearing Capacity Enhancement Effect According to Tip Elements (선단 고정 지압구의 거동 메커니즘과 형상에 따른 지지력 증대효과 검증을 위한 3차원 수치해석)

  • Lee, Seokhyung;Kim, Seok-Jung;Han, Jin-Tae;Jin, Hyun-Sik;Hwang, Gyu-Cheol;Lee, Jeong-Seob
    • Journal of the Korean Geotechnical Society
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    • v.38 no.9
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    • pp.53-67
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    • 2022
  • Micropiles are cast-in-place-type piles with small diameters. They are widely used for the foundation reinforcement of existing buildings and structures because this technique is easy to construct and economic. A base expansion structure is developed following the mechanism of radial expansion at the pile tip under compression. Numerical analysis, durability tests, and centrifuge tests have been conducted using the base expansion structure. In this study, three-dimensional numerical modeling was performed to describe the behavioral mechanism of the base expansion structure using steel bar penetration under compressive loading, and numerical analyses using centrifuge test conditions were performed for the comparative studies. Additionally, the base structure was modified based on the results of lab-scale analyses, and the bearing capacities of micropiles were compared using field-scale numerical analyses under various ground conditions.