Study(I) on Development of Charts and Formulae Predicting Allowable Axial Bearing Capacity for Prebored PHC Pile Socketed into Weathered Rock through Sandy Soil Layer - An Analysis of Sharing Ratio of Skin Friction to Total Bearing Capacity (SRF) by Analyzing Pile Load Test Data -

Yongkyu Choi; Wonje Lee; Chang Uk Lee; Oh-Kyun Kwon

doi:10.7843/kgs.2019.35.8.17

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2019 Vol.35, Issue 8 Preview Page Next Page

Research Article

Study(I) on Development of Charts and Formulae Predicting Allowable Axial Bearing Capacity for Prebored PHC Pile Socketed into Weathered Rock through Sandy Soil Layer - An Analysis of Sharing Ratio of Skin Friction to Total Bearing Capacity (SRF) by Analyzing Pile Load Test Data - 사질토층을 지나 풍화암에 소켓된 매입 PHC말뚝에서 지반의 허용압축지지력 산정도표 및 산정공식 개발에 관한 연구(I) - 재하시험 자료 분석을 통한 전체지지력에 대한 주면마찰력의 분담율(SRF) 분석 -

31 August 2019. pp. 17-30

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Abstract

실제 시공된 말뚝들의 재하시험 자료 및 매입 PHC말뚝의 설계 자료로부터 전체지지력에 대한 주면마찰력의 분담율인 SRF를 분석하였다. 현장에서 시험 시공된 말뚝의 SRF는 말뚝의 종류, 상대근입길이, 지반의 종류, 재하시험의 종류에 상관없이 42∼99%이었다. 매입 PHC말뚝에 대한 설계 자료에서 구한 SRF는 말뚝의 직경, 상대근입길이에 상관없이 풍화암에 소켓된 경우 20∼53%의 범위에 분포하였다. 사용말뚝으로 실제 시공된 매입 PHC말뚝에서 재항타 동재하시험 자료로부터 구한 SRF는 말뚝의 직경, 상대근입길이, 지반의 종류에 상관없이 4∼83%의 범위에 분산되어 분포하였다. 사용말뚝에서 SRF가 낮은 수준으로 나타나는 이유는 매입 PHC말뚝의 주면고정액의 충전이 제대로 이루어지지 않은 채 시공된 현황으로 볼 수 있었으며 따라서 주면고정액의 시공관리에서 시급하게 개선해야 할 현황이었다. 풍화암에 소켓된 매입 PHC말뚝의 설계에서 사용하고 있는 극한지지력 산정공식으로 계산한 주면마찰력의 SRF는 실제 현장 시공 말뚝의 보다 평균적으로 2.2배 정도로 낮은 수준으로 평가되었다. 이는 설계에서 사용하고 있는 산정공식에 의한 극한주면마찰력이 매우 낮은 수준으로 계산되기 때문이다. 따라서 SRF를 만족시킬 수 있는 새로운 주면마찰력 산정공식의 제안 필요성이 있는 것으로 판단된다.

Based on pile load test results for various pile types that were constructed in-situ and pile design data of prebored PHC piles, the ratio of skin friction to total capacity (SRF) was analyzed. A SRF distribution range from the pile load test results for pilot test prebored PHC piles was 42∼99% regardless of relative penetration lengths, soil types, and pile load test types. However, a SRF distribution range from the pile design data for prebored PHC piles was 20∼53% regardless of relative penetration lengths and pile diameters. Also, a SRF distribution range from the restrike dynamic pile load test results for pretest working prebored PHC piles was a scattered range of 4∼83% regardless of pile diameters, relative penetration lengths and soil types. The scattered SRF of pretest working piles was caused to the quality control issue on the filling of cement milk around piles and this quality control issue should be improved. The average SRF calculated by the current design method was estimated to be 2.2 times lower than the average SRF of the pilot test piles. It is because skin friction resistance is calculated at a very low level. Therefore, a new design method for skin friction will be proposed based on this study.

Keywords

Pile load test data analysis

Current design data anlaysis of prebored PHC pile

Sharing ratio of skin friction to total capacity (SRF)

SRF of prebored PHC pile

Necessity of a new design method for skin friction

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Information

Publisher :The Korean Geotechnical Society
Publisher(Ko) :한국지반공학회
Journal Title :Journal of the Korean Geotechnical Society
Journal Title(Ko) :한국지반공학회 논문집
Volume : 35
No :8
Pages :17-30
Received Date : 2019-06-04
Revised Date : 2019-08-17
Accepted Date : 2019-08-19
DOI :https://doi.org/10.7843/kgs.2019.35.8.17

Journal of the Korean Geotechnical Society ISSN:1229-2427(Print) 2288-646X(Online) 한국지반공학회 논문집

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