Improvement of soil stability along rail corridors through native vegetation

Field studies have revealed the effective utilization of native trees as an economical and environmental friendly method of soil stabilization along railway lines in Australia. Native trees grown along rail corridors are capable of providing mechanical strength to the subgrade soil through the root network and the additional cohesive increment provided by the osmotic suction generated at the hair roots. Moreover matric suction generation due to evapo-transpiration of the tree canopy has significant influence on shear strength of soil underneath the railway lines. Therefore the true effect of vegetation should be evaluated considering the mechanical root reinforcement effect, evapo-transpiration induced matric suction development and in addition the alteration of potential failure conditions in the soil-root system from a saturated to an unsaturated domain. This paper will discuss the requirement of a shear strength model that combines the root reinforcement effect with both osmotic and matric suction components generated in the soil through naturally coupled osmotic evapo-transpiration phenomenon.