Determining effects of vegetation on slope stability with experimental studies

Ensuring and maintaining slope stability is one of the main subjects in geotechnical engineering. Addressing this issue through nature-based solutions, which offer an innovative perspective, can provide multifaceted contributions for the future, both economically and ecologically. The increasingly prominent method of vegetation-based slope stabilization is investigated through various experiments and analyses conducted on plant roots. The influence of vegetation on slope stability stems from the mechanical and hydrological effects of small-diameter (flexible) and large-diameter (rigid) roots. The hydrological effect includes the evaporation and water uptake processes necessary for the physiology of plants, while the mechanical effect is based on the anchoring effect of large roots and the increase in the general root-soil compatibility of fine roots. Within the scope of this thesis, systematic studies were conducted to reveal the effects of vegetation methods on slope stability. Based on previous studies in the literature, various root parameters such as root diameter, root cohesion, root tensile strength and root distribution depth were considered. In order to determine these parameters, direct shear and pull-out tests were performed on samples prepared with olive roots and root distribution data were also recorded from observation pits excavated for sampling. Using the obtained parameters, different scenarios were modeled on a specified slope geometry and the factor of safety was calculated for each case. The effects of plant roots on slope stability were evaluated comparatively. According to the analysis results, the safety factors of vegetated slopes showed a significant increase, especially due to the enhancement of cohesion. A cohesion-effect chart was developed based on the obtained data to facilitate its use in modeling studies. The findings suggest that if vegetation is selected according to root morphology and appropriately modeled for the project, it can offer a sustainable and environmentally friendly solution to mitigate the risk of shallow landslides.