双荚决明不同弯曲程度单根抗拉变形特性

[Objective]In the southwest Karst areas,most of the plant roots exist in the form of bending.The previous studies mostly selected uniform and straight root systems,but the tensile characteristics of bending roots are unknown.The mechanical properties of bending roots could helps to reveal the root soil solidification mechanism.[Method]The 5-year-old slope greening tree species Cassia bicapsularis was used to explore the mechanical properties of solid soil with different degrees of bending and reveal the mechanism of slope protection of solid soil.[Result]1)The tensile force and tensile strength of C.bicapsularis root system under different degrees of bending were shown as straight roots>slightly bending roots>bending roots,and the ultimate elongation was bending root(29.26%)>slightly bending roots(21.15%)>straight roots(12.14%).2)The tensile deformation process of C.bicapsularis bending root was complex and diverse,and its stress-strain curve was mainly divided into monomodal and multimodal type.The single root was used preposition,elastic deformation,plastic deformation,yield and root bark tearing five stages to resist deformation,and one more preposition than the straight root.The strain will be generated after the stress at this stage produces a certain value,and the stress interception range is 0.03～5.7 MPa.In the early stage of force on straight roots,the stress increased rapidly with strain,and was"convex"in the stage of elastic deformation,while the bending root was"concave"and the stress increased slowly with strain,which is manifested as the"buffering"of slope protection of solid soil in the bending root system.3)The initial force displacement of C.bicapsularis bending root was positively correlated with the degree of bending;It was manifested as a part of the soil pressure shared by the bending root when deformed by force than the straight root,and the magnitude of this part of the force was directly affected by the degree of bending.The initial force displacement of the bending root was less than the length of the bending part,that was,the tensile force was generated before the bending root was not straightened;The bending form was that the stretching of the bending root stores part of the prestress,and when a shallow landslide occurs,the force was released first by the bending part,showing the"preposition"of the bending root to consolidate the soil slope.[Conclusion]The tensile deformation process of C.bicapsularis bending root was quite different from the straight root,and it showed better slope protection characteristics than the straight root.The results of this study provide reference significance for the evaluation of mechanical properties of bending roots.