Dynamic control test on micropiles

We were commissioned by Franki Fondation, based in Chaponost (69), to carry out a control test on micropiles using low-stress dynamic loading.

This new test was developed by us in partnership with the Fédération Nationale des Travaux Publics and the University of Clermont Ferrand. The characteristics of the micropile are: type III, borehole diameter 200mm, reinforcement tube diameter 60.3mm, length 9.2m and load-bearing capacity of 23T at serviceability limit state (SLS). The test is carried out up to 1.3 times its ELS load.

The test consists of applying a series of shocks of increasing energy to the head of the micropile, which has been instrumented beforehand (installation of sensors on the micropile reinforcement). The impact energy is increased either by increasing the drop height of the mass (here 240kg from 0.10m to 0.45m), or by increasing the mass of the “hammer”. The signals recorded can then be used to determine the static force as a function of the elastic displacement and to check the conformity of the micropile. At the same time, a laser level pointed at the foundation can be used to check that the integrity of the micropile has not been compromised.