Full scale experimental assessment of the dynamic horizontal behavior of micropiles in alluvial silty soils

The paper deals with an extensive experimental campaign of dynamic tests performed on full-scale vertical injected and not injected micropiles embedded in alluvial soils. The experimentation includes ambient vibration and impact load tests to investigate the dynamic behaviour of the soil-micropile system in very small and small-medium strain ranges, as well as snap back tests to investigate the evolution of the post-elastic response of the system. Micropiles are instrumented with strain gauges along the shaft, accelerometers and displacement transducers at the head. Modalities and results of the different performed tests are presented, focusing on the role of high pressure injections on the dynamic behaviour of the system, on the development of non-linear soil-pile phenomena, and, finally, on the evaluation of effectiveness of the different testing procedures to capture the dynamic response of soil-micropile systems. Ambient vibration test revealed to be a versatile method to identify the dynamic properties of soil-micropile systems, although it requires demanding post-processing techniques of data. Impact load test is faster to perform and easier to post process. Free vibration test proved to be relatively simple to perform and able to catch the dynamic non-linear behaviour of soil-micropile systems.