ABSTRACT:
The challenge when regarding the forest stand as a protection barrier against rockfall is to assess and predict its protection effect. To investigate this, full-scale impact tests, which simulated the interaction between a single tree and an impacting mass (trolley), were done in its natural environment. It was shown that the complex interaction between the simulated rock and a single Norway spruce tree (Picea abies (L.)Karst.) can be modelled with finite elements. By performing parameter studies using the developed model, the energy absorption capacity Ecap of a single Norway spruce tree as a function of diameter at breast height DBH and the position of the flying rock in terms of impact height Himp, eccentricity ?, and impact angle aimp could be calculated.
1 INTRODUCTION
A natural protection against falling rocks can be the forest growing on mountain slopes. Its importance has been recognized a long time ago and is highlighted by several authors (Kienholz & Mani 1994, Stoffel et al. 2005). The challenge when regarding the forest stand as a protection barrier is to assess and predict the protection function of the forest. A single tree dissipates energy during and after a rock impact in several different ways: rotation and translation of the root system, deformation and oscillation of the tree stem, and penetration of the rock at the impact location (Brauner et al. 2005, Dorren & Berger 2006). The behaviour of the root-soil plate under a static load has been studied for many years (Fraser & Gardiner 1967). The ultimate bending moment for the root system depends on the mass of the root-soil plate, the failure strength of the soil, the resistance to failure in tension for tree roots on the windward side, and the bending resistance of the tree leeside roots (Blackwell et al. 1990).
