Experimental investigation into the influence of root diameter and dry-wet cycle on the shear strength of root-soil composite
This study investigates the reinforcing effect of the roots of vegetation on the soil,and the mechanism of weakening of the root-soil composite when subjected to wet-dry cycles,with the aim of providing suggestions for the ecological management of slopes for disaster prevention.We conducted triaxial tests on root-soil composite samples featuring roots with varying diameters that were subjected to wet-dry cycles.The microstructure of the composites was analyzed by using electron microscopy.The results showed that the tensile strength of fresh,saturated,and dry roots decreased according to the power law with increasing root diameter.Dry roots exhibited the highest tensile strength,followed by fresh and saturated roots.The stress-strain curve of the root-soil composite reflected continuous hardening behavior.As the strain increased,the deviatoric stress initially increased rapidly and then slowly,and eventually stabilized.The shear strength of the root-soil composite first increased and then decreased as the diameter of the roots increased.However,when the root diameter was too small or too large,the reinforcement effect of the roots on the soil weakened.The root system significantly altered the cohesion of the soil but had little impact on the internal angle of friction.Its shear strength increased with the confining pressure but decreased with an increase in the number of dry-wet cycles.As the latter increased,the shear strength and cohesion decreased linearly,the soil aggregates were decomposed,and the area occupied by cracks and pores increased exponentially.The root-soil composite exhibited a shear dilation-based pattern of failure.The results showed that considering the influence of dry-wet cycles can enhance the accuracy of the model for predicting the strength of the root-soil.The predictions of our model were in good agreement with experimental data.