Impact of Root System on Soil Strength in Shallow Landslide

Abstract

The main aim of this study was determination of tree root architecture and its influence on soil reinforcement on the case of shallow landslide activated in May of 2010 in Polish Flysch Carpathians. The research was divided into few stages: recognition of geotechnical conditions of analyzed site, determination of root area ratio (RAR) of tress using trench wall method, laboratory tensile tests of root samples, shear strength tests of non-reinforced and root reinforced samples, characterization of soil microstructure by high resolution X-ray computed microtomography (mXCT). The site investigations revealed surficial soil layer, which is composed of silt and silt-loam soil. RAR measurements showed the significant decrease of root number with the depth. Maximum value of RAR was equal to 0.25%. The direct shear apparatuses were used for shear strength tests of rooted samples. The roots cause slight increase of internal friction angle and cohesion values. The mXCT method provide evaluation of the density and orientation of the roots in the sample. This data enabled for more accurate assessment of the root effect on the development of shear stress within soil.