Title : Investigating Vetiver plant Eco physiology and shear stress changes in different regions in Iran
Abstract:
By increasing the shear strength of the soil, Vetiver roots increase the stability of the earthen roofs. In general, Vetiver root as a soil reinforcement agent reduces the shear stress in the soil by distributing the load between the soil grains. On the other hand, by converting its tensile strength into force along the cut, it increases the shear strength in the mass. In addition to root density in the soil, this increase is a function of its performance during rupture. Therefore, in order to evaluate the effect of Vetiver root density on the stability of soil terraces, in addition to the mechanical properties of the soil, information on the number, diameter and tensile strength of the root as well as the angle of its shape change in the soil is necessary. In this study, the effect of Vetiver root on the stability of soil slopes in different regions has been investigated. The basis of the work is the analytical model of the stability of rooted soils, and the required information about soil and roots was obtained through cutting tests on rootless and rooted soils. The location of this research has been in several different climates, slopes and
soils. After the completion of each test, in the shear zone of the sample, while counting the number of roots, the diameter and angle of shape change of each one were measured. Also, based on the theory of direct cutting test, adhesion parameters and friction angle of soil mass with roots and without roots are calculated. After 5 years of Vetiver planting, the amount of humus and organic matter of the soil was measured in the three target areas by repeating 57 samples and compared with the amount of humus and organic matter of the soil 5 years ago. During the same period, direct shear stress was measured in 57 soil samples with Vetiver plant roots and 57 soil samples without Vetiver plant roots in a laboratory environment. The results of this research show that in the semi-arid region, compared to the temperate cold mountainous and humid mountainous regions, the highest amount of humus and organic matter changes in the soil texture was observed. Therefore, in the semi-arid region, due to the increase in humus and soil organic matter caused by the growth of Vetiver plant roots, the shear stress resistance in the soil increased.
Keywords: Soil, humus, organic matter, vetiver, shear stress
