• Period | 2006 - 2012
  • Country | Norway
  • Market | Building, construction and transportation
  • Project Manager | Kjell Karlsrud
  • Partner | Multiconsult
  • Client | The Research Council of Norway
R&D program|

Time effects on pile capacity

In 2006 NGI initiated a research project "Time effects on pile capacity", motivated by evidence from past field testing of a considerable gain of the axial bearing capacity of piles with time.
Develop design guidelines
for piles
that accounts for gain in capacity
due to time effects.

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Gains of 10 to 50 % have been reported over a period of two years, and 50 to 100 % after 10 years. The project goal is to develop design guidelines that accounts for time effects. This will be achieved through a systematic test program, where piles at five different sites over a time period of two years is tested. The site conditions cover soft and stiff clays and loose to medium dense sands.

The work is organized as a Knowledge-building Project with User Involvement (KMB) with about 35 % funding from The Research Council of Norway (RCN). The rest is financed by various industry partners with a significant portion from Offshore Energy Companies. Multiconsult AS acts as project partner towards RCN, and NGI has the full responsibility for planning, and execution of the project.

Background

The main objective of the project is to establish design procedures that accounts for increase in the axial bearing capacity of piles with time. Such anticipated gain in pile capacity is not incorporated in existing Design Codes like the American Petroleum Institute's (API) for offshore structures.

Background pileinst Helsinki 590

Piling at Helsinki waterfront (Photo from the Ruukki website)

If anticipated increase in bearing capacity with time can be accounted for in design, it will open new possibilities for upgrading of piled offshore structures, bridges or other structures which in its lifetime may warrant modifications that increase the loads on the foundations.

Accounting for expected increase in pile capacity with time would also have a positive impact on the "first time" design of pile foundations. For structures it often takes from several months and up to a year or two from piles are installed to the structure is completed and the full design loads are applied. This is commonly the case for bridges, and also for some offshore structures.

There is little doubt that accounting for this potential gain in pile capacity with time has a potential for very significant direct and indirect cost savings. In cases where new and heavier production facilities are required for an offshore field re-development, one might eliminate the need of a new jacket structure if the existing one can be up-graded. Savings could then be of the order of several hundred million NOK. Potential savings for Norwegian bridges and land-based structures could average in the range of NOK 5 to 50 million per year.

The project has the following sub-objectives:

  • Review of all relevant existing data
  • New pile load tests specifically designated to reveal time effects
  • Detailed planning and selection of test sites
  • Establishing instrumentation and monitoring systems
  • Site preparation and testing arrangements
  • Execution of tests
  • Development of new design procedures and ensuring that they will be incorporated into national and international design codes.

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Organization of Project

The project will be run by a consortium (steering committee) consisting of participants from the participating companies/sponsors. The consortium will be headed by Arne Schram Simonsen of Multiconsult AS, which has the formal contract with The Research Council of Norway. 

Org kart

 

NGI is the technical responsible for the project, with Technical Director Kjell Karlsrud as project manager. He was also project manager for the major pile research programs undertaken by NGI in the 1980's and 1990's, and was instrumental in developing some of the new design procedures which were implemented in the Norwegian Pile Design Guidelines issued by the Norwegian Geotechnical Society in 2005. He has also published many papers on pile bearing capacity and authored the chapter on Pile Bearing Capacity in the Norwegian Pile Design Guidelines, 2005.

New participants are welcome

The project group still welcomes more participants to the project, both as industry partner which primarily contribute with funding and companies that both contribute with technical support for execution of the projects tasks and funding.

Deltakere og sponsorer

 

Project activities

The project has the following main activities:

  • Detailed project planning and project management, updating of present knowledge and data base on piles and test site selection
  • Site selection and investigations, including characterisation of soils with in situ and laboratory testing
  • Instrumentation of test piles, load cells and data acquisition system
  • Site preparation, including pile purchase and installation, construction of loading frames, provision of equipment and site clearing at the end
  • Execution of pile load tests and factual reporting
  • Assessment of results, interpretation of new load tests and older data, development of design procedures, reporting, dissemination to industry and regulatory agencies and preparation of papers.

Prelimininary results from the pile tests were subjected to confidentially clauses in the contracts with the industry partners providing financial support to the project. It was therefore not possible to publish results from this Project during the course of the project. The final report, below, presents a comprehensive description of the project and the results.

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