Back Ground

Several aspects of pile response to axial load are still not fully understood and need to be further investigated.
A number of methods for the prediction of the axial capacity are available in the literature, frequently based on experimental results collected by load tests on full scale instrumented piles. These methods generally supply values for “lumped” coefficient to be used in very simple equations to evaluate unit shaft friction and base resistance as a function of the pile type/soil type combination. More detailed information on the load transfer mechanism from pile to soil have been obtained by accurate research, mainly conducted on model pile inserted in a soil box (1-g lab) or in centrifuge tests. Very rarely these studies have been carried out at full scale level.
The main scope of the present research is the investigation of the complex pile-soil interaction mechanisms which develop at pile shaft and base during static axial loading.


Experimental testing site


At the experimental site, 6 testing piles have been executed with different technology (bored, with bentonite or polymer mud, and Continuous Flight Auger, CFA), lengths (15 to 24 m) and diameters (0.7 to 1.0 m). All piles are fully instrumented along the shaft by means of wire stain gauges and steel tubes. The latter will be used both for integrity testing and for the placement of retrievable multiple extensometers.
The testing piles have been static axially loaded: 5 of them by means of the standard procedure, with reaction piles (14 CFA piles, D = 0.8 m and L = 24 m), and 1 by means of the Osterberg Cell.