The effect of roots on soil reinforcement

Recent years have seen an increase in catastrophic incidents due to slope instability problems in Europe. Heavy rains and floods on barren soil are
common triggers for mass wasting, while forest fires and high winds are
devastating the soil under vegetation cover during hot and dry summers, such
as the ones in the Mediterranean area, increasing soil exposition to instability.
Vegetation plays a very important role in soil stabilisation. It has a direct
influence on the soil by protecting it and restraining it near the surface,
increasing its strength in the deeper soil layers, and influencing its hydrological
cycle. These effects can be either beneficial or adverse for the soil stability,
and knowledge of the processes which occur in the soil as a result of the
presence of vegetation could enable minimisation of the adverse effects in
favour of stability.
Stable, well anchored plants are required for application on instability-prone
slopes in order to keep the soil mass from sliding and in the same time
providing necessary stability for the plant. The effect of vegetation roots on
the soil stability is reviewed, and new investigations on the behaviour of root
systems under different types of loading are presented.
This paper presents work investigating the link between root systems, root
mechanical properties and soil strength. A number of root-soil interaction and
element have been designed and carried out in order to understand how the
roots interact with the surrounding soil to increase the strength of the rootsoil
composite system. Initial results show that the presence of roots greatly
improves soil strength and that the magnitude of reinforcement depends on root
and soil mechanical properties, as well as on the root geometry and placing.