Effect of Cyclic Axial Loading on the Distribution of Load along a Pile

In France, the standard for the design of deep foundations is being updated with new requirements on the effect of cyclic loading. As no design method exists to take into account this type of loading, a research project was launched (SOLCYP). The field test part of this project consists of an experimental program with compression and tension full-scale pile test undertaken to study the behaviour of piles under cyclic loading. The main feature of the field tests will consist in measuring the distribution of load (shaft and toe resistances) along the pile during static and cyclic tests. To achieve this scheme, the use of the LCPC (French Public Works Research Laboratory) removable extensometer is required. It was tested for cyclic tests for a frequency up to 1 Hz. One of the main objectives is to point out pile bearing capacity degradation and cumulative displacement due to repetitive service loads. This paper summarizes preliminary full scale compression tests achieved in 2008. It shows the good reliability of the monitoring method to get the distribution of load along the pile during cyclic loading from 0.1 to 1 Hz frequencies load controlled tests. From the measurements of the load segments, the load was fairly distributed along the pile. As far as cumulative displacement is concerned, the pile response depends on the number of cycles, the load amplitude and loading history.