Study On The Deformation Feature And Destruction Feature Of Three Kinds Of Shrubs Root In Semi-arid Mining Area

In this study,3 kinds of shrubs in Semi-arid mining area:Caragana microphylla Lam.,Salix psammophila and Hippophae rhamnoides L.were selected as subjects,using the TY8000 servo power machine investigated the deformation feature and destruction feature of the straight roots and lateral roots(diameter at 1?5mm)of three shrubs.This study enriched the mechanical mechanism of soil-reinforcement by shrub root system,and provided important theoretical basis for vegetation restoration and construction in coal mining subsidence areas.The main conclusions in this study are as follows:(1)Under a single load,the average tensile-shear combined strength of straight roots of Caragana microphylla Lam.and Salix psammophila were greater than the average tensile strength(46.39?39.96MPa,23.55?17.86MPa),and the results of the lateral roots were as same as straight roots(34.70?29.86MPa,14.16?11.43MPa).But the results of Hippophae rhamnoides L.were different from the first two plants.The average tensile-shear combined strength of the straight roots and the lateral roots of Hippophae rhamnoides L.were smaller than the average tensile strength(9.83?12.43MPa,8.18<8.90MPa).In summary,the vulnerable loads of the straight roots and lateral roots of Caragana microphylla Lam.and Salix psammophila were axial tension force,while Hippophae rhamnoides L.were tensile-shear combined force.(2)The average tensile strength of 3 kinds of shrubs test roots all manifested as:the adjacent upper straight roots>the adjacent subordinate straight roots? the lateral roots(Caragana microphylla Lam.:40.63?38.40?28.77MPa;Salix psammophila:17.36?16.84?11.53MPa;Hippophae rhamnoides L.:11.85?11.44?8.77MPa).The average tensile-shear combined strength of 3 kinds of shrubs test roots were the same as tensile strength(Caragana microphylla Lam.:45.34>44.97>38.31MPa;Salix psammophila:23.06?21.28?15.13MPa;Hippophaerhamnoides L.:9.52?8.81?8.05MPa).That is to say,the vulnerable parts of the roots of the three shrubs all were the lateral root branches.(3)The tensile force and tensile-shear combined force of the straight roots and lateral roots(diameter at 1?5mm)of 3 kinds of shrubs increased with root diameter,and the tensile strength and tensile-shear combined strength decreased with root diameter.The tensile force,tensile strength,tensile-shear combined force and tensile-shear(4)combined strength of the root systems of 3 kinds of shrubs were significantly different among species,which were all manifested as:Caragana microphylla Lam.>Salix psammophila>Hippophae rhamnoides L..(5)Regardless of repeatedly loading and unloading axial tension force or radial tensile-shear combined force,the F?S curve of the straight roots and lateral roots(diameter at 1?4mm)of 3 kinds of shrubs all showed Elastic-plastic characteristics.(6)At the same loading speed,the average number of loads and the average extension rate of the straight roots and lateral roots(diameter at 1?4mm)of 3 kinds of shrubs increased with increasing diameter level.But the straight roots of Caragana microphylla Lam.,in contrast,the finer straight roots(diameter at 1?2mm)has a stronger tolerance for repeatedly load-unload axial tension force,and the 2?3mm straight roots has a stronger tolerance for repeatedly load-unload radial tensile-shear combined force.At the same diameter level,the average number of loads and the average extension rate of the straight roots generally greater than lateral roots.(7)The constitutive curve types of the root systems of the three shrubs(diameter at 1?5mm)under single loading are convex curve,wave curve,multimodal curve,straight curve,and concave curve.The convex curve and wave curve are the main deformation types.