Mechanical Properties Of Root-soil Composite System Of Clay Slope

In the ecological slope engineering,it is the premise to ensure the stability of the slope to make clear the mechanical properties of the roots and its interaction with the slope soil.At present,mechanical characteristics of roots of plant and root-soil composite system haven't formed a complete theoretical system.Firstly,tensile tests of typical slope protection plants were carried out to analyze their tensile properties.Secondly,the growth environment of slope plants was simulated,and pot planting test was carried out to study growth status of plant seeds and shear strength of root-soil composite samples under different cover thickness.Thirdly,stress characteristics and strength variation of the root-soil composite samples under different drying-wetting cycles were analyzed.Finally,a new formula for calculating shear strength of root-soil composite system was derived,and the following main conclusions are drawn:(1)Tensile peak value of plant roots increases with increase of diameter,and tensile strength of most plant roots decreases with increase of diameter,and logarithmic function and power function can better describe the relationship between tensile strength and diameter of plant roots.(2)Optimum growth depth of Bermuda grass is 2 cm.When thickness of overburden is 2 cm,root length density and root biomass concentration have peak value,and shear strength of root-soil composite of plant unit also reaches the maximum value.With the change of soil depth,internal friction angle of root-soil composite has no obvious change,while cohesion has obvious change,and cohesion is positively related to the root biomass concentration.(3)Number of drying-wetting cycles has a significant effect on the shear strength of root-soil composite samples.After drying-wetting cycles,cohesive and internal friction angle of root-soil composite have the same weakening trend,and weakening rate of cohesive force is higher than that of internal friction angle.(4)The main principle of strengthening slope with main straight root plants are the reinforcement and anchorage.When normal stress is constant,shear strength of composite soil increases with the increase of reduction coefficient.When reduction coefficient is between 0.84 and 0.86,the results are close to the measured values.When normal stress increases,shear strength of the composite increases.The relative error between the shear strength calculated by the theoretical formula and the measured value is within 10%.The conclusion has certain theoretical significance and reference value for enriching the theory of slope ecological protection technology and promoting the development of slope ecological protection technology.