Forests are an efficient natural protection mean against rockfall. Previous studies have been focused on the analysis of the protective function of forest and, more particularly, the tree capacity to dissipate the rocks energy. In forested areas, maintenance of forests is needed to ensure their protective function and health. During this process that consists in removing some trees, the protective capacity of the forest decreases. To compensate the temporally loss of protection, some of the felled trees are left in an oblique position to the slope. It is a financially feasible solution to ensure the protection against rockfall during the regeneration of the forest. So, felled trees can become a useful protection system if correctly placed. No studies have been done concerning the efficiency of these devices and particularly their resistance to rock impacts and their energy dissipation capacity. So, the aim of this project is to study the impact phenomenon to determine the efficacy of these devices. Fresh wood rheology has to be characterized to quantify felled trees response to a rock impact. Contrary to dry wood, which has been analyzed in detail because of its importance in construction, few studies concerning the rheology of fresh wood and its mechanical properties under dynamical loading can be found in literature. Numerical impact simulation programs are largely used in civil engineering for structure design and study. Even if numerical simulations allow faster, cheaper and precise results, experimental tests are still needed to validate the numerical models. Due to the complexity to carry out in-field tests and to obtain precise results, laboratory experiments became a good way to simplify the studies and to control the environment parameters.