Static and dynamic pulling tests on a real scale tree: mechanical characterization and simplified preliminary interpretation

Understanding the complex hydro-mechanical processes governing the soil-root interactions has a pivotal role in several research areas and in particular for a relatively recent field of research concerning the assessment of the uprooting re sistance of trees. The risk associated with falling trees is a newly emerging issue for risk management procedures in urbanized areas, which is also severely impacted by the ongoing climate changes. Several techniques are available for professional agronomists to assess the stability of a tree and in the last thirty years, together with other non-destructive experimental approaches, tree pulling tests have become a rather diffuse method to characterize the behaviour of a tree subjected to lateral loads. Despite such a wide use, their mechanical interpretation is still based on simplified phenomenological expressions, without considering the site environmental conditions, and limiting the analysis to simple monotonic loading paths. In the paper, the results of a more advanced loading scheme for a pulling test are presented. Test results considering cyclic quasi-static loading conditions and controlled dynamic conditions (imposed by a sudden stress release) are presented and critically interpreted on the basis of simple mechanical models. The results suggest that the governing mechanical parameters may be remarkably affected by soil conditions and SVA interaction and that simple 1dof interpreting models may not properly capture the observed behaviour.