Study On Soil Mechanical Properties Of Herbaceous Plants In Rocky Mountain Area Of Shanxi Province

Landslides due to soil erosion are common natural geological disasters all over the world.Planting plants on hillsides effectively is an important soil and water conservation project in urban construction and mountain development.The article is based on the theories of mechanics of materials,soil mechanics,elastic-plastic mechanics,soil and water conservation,mathematics and plant community.The technical routes combined field test and laboratory test,experimental analysis and theoretical analysis.Doing quadrat survey and important values analysis of herbs in northwest mountain area of Taiyuan,Shanxi Province.Among all the plants,Lolium perenne L.,Vetiveria zizanioides L.and Paspalum notatum Flugge have the higher important values.Using morphology distribution tests and tensile strength tests of roots based on these three plants,the rule of these roots' cross-sectional area and quantity proportion as the changing of depth were studied,and the rule of maximum tensile resistance,ultimate tensile strength and elastic modulus as the changing of ground diameter and root length were also studied.The data were processed by the method of mathematical statistics in order to know its potential significance,based on area proportion and average tensile strength of roots,cohesive force can be calculated.At the last,evaluating the soil fixation ability of different plants and choosing best species for soil and water conservation based on Wu's model.The study involves 9 kinds of herbaceous plants.In order to get the important values of them,the relative frequency,relative density,relative coverage of ground and underground four indexes are required.The important values of Lolium perenne L.,Vetiveria zizanioides L.and Paspalum notatum Flugge are as follows: 29.79%,20.19%,15.95%.The morphology distribution tests showed that the roots of them roughly centered on the neck and radiated in all directions,extended network structures lastly.Most of the roots were distributed in the soil layer about 10-20 cm.Coarse and fine roots also decreased with increasing depth.The tensile strength tests' results showed that,in a certain root length,the maximum tensile strength of three plants increased with increasing root diameter,the single root's ultimate tensile strength decreased with increasing root diameter;and in a certain root diameter,the maximum tensile strength and ultimate tensile strength decreased with increasing root length,the elastic modulus decreased with increasing root diameter and length.Vetiveria zizanioides L.ranked the first on average of the maximum tensile resistance and cohesive force,Paspalum notatum Flugge ranks the first on the average of the ultimate tensile strength and elastic modulus.The results proved that the mechanical properties of single root is an important factor in selecting the suitable slope protection species.All plants researched in hilly area have good mechanical properties.It is assumed that they can play positive roles in the stability of shallow slope.Paspalum notatum Flugge's roots have the best ability of soil protection,it is the most suitable species for soil and water conservation.