Role of hydromechanical properties of plant roots in unsaturated soil shear strength

Plants increase slope stability through mechanical reinforcement by roots and transpiration-induced matric suction (hence increase in soil shear strength; known as hydrological reinforcement). The effects of root water status on root biomechanical properties (e.g. volume change and tensile properties), and eventually the shear strength of rooted soil, have not yet been fully investigated. This paper studies the hydromechanical properties of plant roots and estimates how these properties may affect unsaturated soil strength. The root water retention curve (RWRC), is introduced as a new concept to relate root water content and root suction. Unsaturated shear strength equations are hypothesised to utilise RWRC to couple the mechanical and hydrological reinforcement by plant roots. The potential importance of considering the effects of root hydromechanical properties on soil shear strength is highlighted, together with the need to fully test and develop the underlying models.