ارزيابي تغيير مشخصه هاي مقاومت برشي خاك هاي ريزدانه تحت تاثير تراكم ريشه درخت بيد

Variation of shear resistance parameters in fine grain soils due to willow roots density

Stabilization of river terraces and natural soil slopes in rangelands by means of tree roots as a reinforcement agent is an environmental adopted method which needs to be developed. In this research a series of tests was carried out on soil blocks containing willow roots and without roots using a large scale in situ direct shear test apparatus. The results were analyzed based on direct shear theory to calculate the cohesion and internal friction angle of rooted and non-rooted soil. The results reveal that in spite of a slight decrease of 8% in the internal friction angle, the appearance cohesion of lean clay soils increase significantly up to 130%. The results of this research are presented in forms of linear and logarithmic relations between increased shear strength and root density at different depths of soil.