Project Overview and Organization-Tension Pile StudyProject Overview and Organization-Tension Pile Study
Authors: Chan Jack H-C. , Birrell Norman D. 
Published: October 2008

In 1987, Conoco completed an extensive laboratory and field study on the response of friction piles subject to cyclic tension loading in soft clay. The Tension Pile Research program consisted of four projects conducted over a seven year span, These include 1) Planning Study, 2) Site investigation, 1" laboratory model, and initial small-scale (3" Diameter) pile segment tests, 3) Additional 3" pile segment tests, large-scale (30" diameter) driven pile field tests, analytical interpretation of results and recommendations for pile design, and 4) Long-term retest and pullout of 30" pile. The data collected from all projects are of exceptionally good quality and very complete, These data include static and cyclic load tests on all the aforementioned piles both immediately and a short period following installation, the long term static and cyclic load tests on the 30" pile, and laboratory analyses of the soil layer which adhered to the pile after extraction. This paper presents an overview of the project's objectives, scopes of work, project organization, project milestones, and accomplishments for this multi-year Conoco Tension Pile Study. A slide presentation of some of the highlights of the project activities will also be presented. Technical details of the test set-up, instrumentation, loading mechanism, and test results will be presented elsewhere.

Introduction

In 1981, Conoco was well in the process of design of its first Tension Leg Platform (TLP) in the North Sea, Hutton field, and was considering the design of a second TLP in the Gulf of Mexico. Soft clay soil was expected in the Gulf of Mexico, which was quite different from the North Sea stiff clay soil. The behavior and reliability of tension pile anchors in soft clay soil was not known then. The potential degradation of soil resistance resulted from cyclic storm loading, superimposed on the long-term steady-state tensile loading, was also of prime concern to the TLP pile foundation designer, All these had led Conoco Production Engineering Services (PES) to initiate a planning study in early 1981 for performing a series of extensive laboratory and field testing programs on the response of friction piles Subject to cyclic tension loading in soft clay. The planned Tension Pile Research program consisted of four projects conducted over a seven year span. These include 1) Planning Study, 2) Site investigation, 1" laboratory model, and initial small-scale (3" Diameter) pile segment tests, 3) Additional 3" pile segment tests, large-scale (30" diameter) driven pile field tests, analytical interpretation of results and recommendations for pile design, and 4) Long-term retest and pullout of the 30" pile. This paper presents an overview of the project's objectives, scopes of work, project organization, project milestones, and accomplishments for this multi-year Conoco Tension Pile Study, A slide presentation of some of the highlights of the project activities will also be presented, Technical details of the test set-up, instrumentation, loading mechanism. and test results will be presented elsewhere.

Program Objectives

The objectives for the Conoco Tension Pile Study program were mainly twofold:Develop design method for Tension Leg Platform foundations.Study fundamental behavior of long piles in clay soils,