State-dependent reinforcement effect of roots in the root-soil composite subject to shear: Insights from the laboratory experiments and theoretical modeling

Description

A number of direct shear tests have been done to investigate the mechanical behavior of root-soil composite, with consideration of a number of testing factors, including the soil density, pressure level, planting density and root orientation. The roots for testing are retrieved from the Ficus macrocarpa, and the sampling site is located at the Zhuhai campus of Sun Yat-sen University (113º35'15"E, 22º21'21"N, altitude: 10 m). The soil for testing is completely decomposed granite. The results indicate the presence of root tends to inhibit the development of volumetric deformation, but it will lead to the increase or decrease of shear strength, which is jointly governed by the soil density and pressure level. The root orientation i = 60º is identified to be the most proper root planting direction, responsible for the strongest reinforcement effect and a notable deformation suppression effect. Also, the addition of roots into soils has an obvious influence on the stress-dilatancy relation, contributing to the increase of dilatancy coefficient and decrease of constant volume friction angle.

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