This study investigates the influences of root morphology on the pull-out resistance
and shear strength increment of soil-root system for three species of plants commonly used
in the soil and water conservation of slope land. The increment of shear strength of soil/root
system due to roots can be expressed in terms of increment of cohesion of soil mass. According to
the numerical models of soil-root systems of the three plants, one can carry out a series of numerical
simulations of pull-out and direct shear tests. The analyses indicate the simulations of
ultimate pull-out resistance Pmax of soil-root system are in good agreement with measurements.
Meanwhile, the shear strength increments ΔSr due to roots of the three plants are different and
vary with their specific root morphology. The ΔSr values increase proportionally as the basal
diameter increases, in the order: (Subcostate crape myrtle) > (Cotton rose) > (India-charcoal
trema).
Key Words : Soil/root system, numerical simulation, pull-out resistance, shear strength increment.