Stabilising slopes with vegetation: Root biomechanics and experimental technique

The study investigates the mechanical properties of plant roots in relation to slope stabilisation. European Beech (Fagus slyvatica) samples were taken and root tensile strength and Young's modulus measured as a function of root diameter, clamping pressure, strain rate, and cyclic loading. Thicker samples generally required increased clamping pressure to adequately hold the plant tissue without slippage, whilst pressure that was too great caused breakage close to the clamping point. By increasing clamping pressure linearly as a function of root diameter, the success rate was increased. There was no significant effect on tensile strength or elastic modulus of strain rate (1mm/min or 5mm/min), nor of diameter or sampling depth (roots from top soil versus subsoil). Cyclic loading tests show that roots with a stress history behave in much stiffer manner than roots undergoing an initial loading. Roots exhibited viscoelastic properties and a general expression for the relaxation of stresses in the material was derived. A general equation of creep was developed based on Burger's spring and dashpot model for viscoelastic materials.