The Effects Of Repeated Loading-unloading On The Mechanical Properties Of The Combined Tensile-shear Strength Of Roots Of Four Plants Were Studied

Repeatedly-load disturbance is plant roots in frequent erosion resistance forcing common load model in the process,also is foundation of the research of plant sustainable solid soil,to explore the Caragana microphylla,Salix psammophila,Hippophae rhamnoides,Artemisia ordosicaroots repeatedly under external force after the change of material mechanical properties,The root system at the vertical root and lateral root branches within the diameter range of 1?5mm was taken as the object of study.The mechanical properties of the root system were studied by using TY8000 servo strength machine after the root system was repeatedly subjected to 50 times less than the ultimate tensile shear force of the corresponding diameter,The results show:Four kinds of plant roots under low load(30%fitting limit),high load(70%fitting limit),alternating load(low load with high load alternating)repeatedly after loading-unloading effect of ultimate tensile shear group together with root diameter is positively related to the power function,ultimate tensile shear strength of composite with root diameter is negatively related to the power function,similar to a single load function relation.The ultimate tensile shear strength and ultimate tensile shear combined strength of root systems of four plants before and after repeated stress were always shown as C.korshinskii>S.psammophila>H.rhamnides>A.sphaerphala.Different loading conditions had different effects on the tensile shear strength of roots in the process of repeated loading and unloading.Loading speed is 20 mm/min,the four plants tap root under high load and alternating load repeatedly after add-unloading the tensile shear strength of a single load were significantly increased,lateral root branch under high load and repeatedly-after unloading the tensile shear strength of a single load increased significantly,repeated loading high load can markedly enhance the root tensile shear properties.After repeated loading and unloading under low load,the tensile shear strength characteristics of the four plants'straight roots and lateral root branches were not significantly different from that of the single load.Only the ultimate tensile shear strength of the lateral root branches of seabuckthorn was different from that of the single load.When the loading speed was 200mm/min,the roots of 4 plants were destroyed basically 50 times before repeated loading and unloading under high load.The combined strength and ultimate tensile shear strength of the ultimate tensile shear group increased significantly after repeated addition and unloading of low-load loads(p<0.05).In the process of repeated loading and unloading of the four straight roots of plants,the spacing of the force-displacement(f-s)curve on the displacement axis was first sparse and then dense.In other words,with the increase of loading and unloading times,the elastic-plastic deformation of the radial displacement gradually decreased,and the plastic deformation was so small that it could be ignored,while the elastic deformation tended to be stable.The elastoplastic deformation in the first loading is the maximum in the loading process.In the alternating load,the first loading of the low load and the high load have great elastic-plastic change,and then only the loading of the high load can produce plastic deformation.There were differences in the constitutive curves of four plants' taproot roots under single load and repeated loading and unloading.Under single load,the straight fundamental curve is mainly a concave curve.After repeated loading and unloading,the straight fundamental curve is mainly an s-shaped curve.The maximum increase rate(the maximum slope)of the tensile shear force of the constitutive curve under a single load is significantly lower than that under repeated loading and unloading.