Journal of the Korean Geosynthetics Society (한국지반신소재학회논문집)

Korean Geosynthetics Society (한국지반신소재학회)
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Derivation of Flexural Rigidity Formula for Two-row Overlap Pile Wall

2열 겹침주열말뚝의 휨 강성 산정식 유도

  • Choi, Wonhyuk (Department of Civil and Environmental Engineering, Dongguk University) ;
  • Kim, Bumjoo (Department of Civil and Environmental Engineering, Dongguk University)
  • Received : 2018.11.19
  • Accepted : 2018.11.28
  • Published : 2018.12.30
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Abstract

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%.

현재 개발 중에 있는 2열 겹침주열말뚝은 대심도 굴착 시 적용을 위해 2열의 말뚝을 통해 강성을 크게 증대시키고 말뚝 간 엇갈림 겹침부를 통한 연속성 확보로 추가의 그라우팅이 없이 차수벽 역할을 할 수 있도록 고안된 흙막이 벽체이다. 이 벽체는 기존의 주열말뚝벽체에 비해 2열 엇갈림 말뚝 시공으로 단면 형상이 복잡하여 기존의 주열말뚝벽체들에 비해 휨 강성 등 단면 조건에 좌우되는 설계인자의 결정이 용이하지 않다. 본 연구에서는 2열 겹침주열말뚝의 다양한 단면 조건들에 대해서 이론적 방법과 통계적 분석을 통해 간단한 단면 제원, 즉, 말뚝의 직경과 말뚝 간 겹침길이를 이용해 흙막이 벽체의 중요 설계 인자인 휨 강성을 간편하게 산정할 수 있는 계산식을 유도하였다. 개발된 간편 휨강성 산정식은 정밀하게 계산된 휨 강성과 비교해 오차율 3% 이하인 것으로 나타났다.

Keywords

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Fig. 1. Two-row overlap pile wall method

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Fig. 2. Tetra-axis auger pile wall section

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Fig. 3. Definition of second moment of area and parallel axis theorem

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Fig. 4. Cross-section of two-row overlap pile wall for calculation of flexural rigidity (different pile diameter)

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Fig. 5. Cross-section of two-row overlap pile wall for calculation of flexural rigidity (different overlap length)

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Fig. 6. Cross-section of two-row overlap pile wall

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Fig. 7. Example of the calculation of flexural rigidity

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Fig. 8. Comparison of flexural rigidity for different crosssectional conditions

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Fig. 9. Relationship between flexural rigidity and pile diameter for different overlap lengths

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Fig. 10. Relationship between flexural rigidity and overlap length for different pile diameters

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Fig. 11. Relationship between linear regression model and quadratic regression model

Table 1. Results of flexural rigidity by theoretical approach

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Table 2. Regression equations for flexural rigidity of two-row overlap piles with different overlap lengths

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Table 3. Regression equations for flexural rigidity of two-row overlap piles with different pile diameters

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Table 4. Comparison of theoretical flexural rigidity and estimated flexural rigidity

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