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The aim of this work was to evaluate the roots influence on the shear strength of a clay soil and a sandy soil. Soil samples with and without roots were collected from experimental plantations of Atlantic Forest native species. The soil samples were then physically characterized and their shear strength tested in a laboratory. The results indicated that the soils’ shear strength and compressive strength were increased by the roots. In the sandy soil, roots influenced the shear strength by increasing the cohesion value (234%), while in the clay soil they influenced the shear strength mainly by increasing the cohesion value (32%) and the internal friction angle (14.4%). This information can ultimately be part of the technical justifications that ratify the use of plants in erosion control and slope stabilization works.

The aim of this work was to evaluate the development of shrub live cuttings and their effect on slope stability. Vertical in situ pullout tests and measurements of Phyllanthus sellowianus shoots and roots of 2, 4, 6, 8, 10 and 14 months old were conducted. Stability analyses were conducted for slopes with planar and curved rupture surfaces and for soils with and without plants. The results showed that seasons affected plants growth and their ability to provide soil strength. Soil shear strength values ranged from 4.5 kPa (2 months old) to 47.6 kPa (14 months old). The critical factors of safety (FS) for slopes for both planar and curved rupture surfaces were found in the absence of plants and reached the stability condition (FS>2) with plants at 4 (planar) and 6 (curved) months old.