As part of the French national research project SOLCYP, an extensive series of static and cyclic axial pile load tests has been carried out in the overconsolidated Flandrian clays from northern France (Merville experimental site). Tests were performed on 4 driven closed-ended pipe piles (with a depth of 406mm, length of 13m and wall thickness of 15mm); 4 bored piles; and 2 screwed piles (with a depth of 420mm and length of 13m). All piles were instrumented with retrievable extensometers for measuring the load distribution along the pile wall. The paper describes the context of the pile tests and presents preliminary static and cyclic test results obtained on the driven piles. The example of pile B4 under one-way tension loading is taken to illustrate the type and quality of data acquired.
Cyclic axial and lateral loading on offshore, near shore and onshore structures may be essentially of environmental (e.g. wave, wind) or industrial origin. Loading histories include a large variety of loading modes (e.g. tension, compression, one-way, two way), cycle amplitude and frequencies. A keynote paper in these conference proceedings by Jardine et al. (2012) presents the potential effects of cyclic loading on the response of offshore piles. Practical engineering methods in use in the offshore industry (oil and gas, wind farms) are reviewed. Key aspects that are of interest to the pile designer are as follows: (i) the potential reduction on the ultimate axial capacity; (ii) the number of load cycles of a given load that the pile can sustain before cyclic failure; and (iii) the evolution of displacements of the pile head during cyclic loading (pile stiffness). In the building and civil engineering domain, the effects of cyclic loading on foundation piles are poorly understood and largely ignored in practical design.
