## Abstrakti

The tensile forces affecting pile foundations are usually transferred to the bedrock by rock anchors. If drilled piles could transfer some of these tension forces, foundations could be lighter, execution works easier and the whole system could be more cost-efficient. The aim of the paper is to present the loading tests made for the drilled, grooved pipe piles to define their tensile capacity and to assess their ability to work as tension force transferring structure. The study includes literature review of existing research on tension piles and testing. The review covers the different methods for transferring tensile forces, the geotechnical design of tension piles and the main problems in the design. The testing part focuses on a pull-out test on pipe piles with a grooved surface.

The literature review found several reasons to update current geotechnical design practices on tension piles. It showed that the design methods are conservative and not at an optimal level of precision. In addition, several recent studies have examined the tensile resistance of piles, revealing three main factors affecting bond strength: the relation between the diameter of the drill hole and that of the pile, the roughness of the steel surface and the quality of the grouting. Furthermore, the stresses are not distributed uniformly along the length of the pile, but are highest on the top of the pile and lowest at the tip of the pile. Hence, the bond strength cannot be increased by increasing the bond length. The results of the pull-out test proved that the bond strength of the pile is significantly increased by the grooved surface. However, over half of the steel piles could not be pulled out of the bedrock as loading had to be discontinued at the yield capacity of the steel piles for safety reasons. Thus, the actual tensile capacity of the piles remained undetermined. Anyway the grooved pipe piles proved to have a great potential to be used as tensile force transferring structures.

The literature review found several reasons to update current geotechnical design practices on tension piles. It showed that the design methods are conservative and not at an optimal level of precision. In addition, several recent studies have examined the tensile resistance of piles, revealing three main factors affecting bond strength: the relation between the diameter of the drill hole and that of the pile, the roughness of the steel surface and the quality of the grouting. Furthermore, the stresses are not distributed uniformly along the length of the pile, but are highest on the top of the pile and lowest at the tip of the pile. Hence, the bond strength cannot be increased by increasing the bond length. The results of the pull-out test proved that the bond strength of the pile is significantly increased by the grooved surface. However, over half of the steel piles could not be pulled out of the bedrock as loading had to be discontinued at the yield capacity of the steel piles for safety reasons. Thus, the actual tensile capacity of the piles remained undetermined. Anyway the grooved pipe piles proved to have a great potential to be used as tensile force transferring structures.

Alkuperäiskieli | Englanti |
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Otsikko | NGM 2016 Proceedings |

Alaotsikko | Proceedings of the 17th Nordic Geotechnical Meeting Challenges in Nordic Geotechnic |

Kustantaja | Icelandic Geotechnical Society |

Sivut | 113-122 |

Sivumäärä | 10 |

ISBN (elektroninen) | 978-9935-24-002-6 |

Tila | Julkaistu - 2016 |

OKM-julkaisutyyppi | A4 Artikkeli konferenssijulkaisussa |

Tapahtuma | Nordic Geotechnical Meeting: Challenges in Nordic Geotechnic - Harpa, Reykjavik, Islanti Kesto: 25 toukok. 2016 → 28 toukok. 2016 Konferenssinumero: 17 http://www.ngm2016.com/ |

### Conference

Conference | Nordic Geotechnical Meeting |
---|---|

Lyhennettä | NGM |

Maa/Alue | Islanti |

Kaupunki | Reykjavik |

Ajanjakso | 25/05/2016 → 28/05/2016 |

Muu | The aim of the conference is to strengthen the relationships between practicing engineers, researchers and scientists within the fields of geotechnics, geotechnical engineering and engineering geology with special emphasis on the Nordic region. |

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