| Due to the excavation of traditional slope protection engineering,the original ecological environment of the slope is damaged.Ecological bag reinforced earth retaining wall is a new type of slope retaining structure which combines ecological restoration and slope protection.The shear characteristics of the reinforced soil interface of eco bag have an important influence on the stability of eco bag retaining wall,and the interface strength parameter is an important basis for the engineering design of eco bag retaining wall.Based on the shear test in laboratory,the effect of reinforcement of tall fescue root system on the interface characteristics between eco bag and soil was studied,and the constitutive model of the interface between eco bag and soil reinforced by tall fescue root system was established:(1)The interfacial cohesion,internal friction angle,interfacial friction coefficient and equivalent shear stiffness decrease with the increase of water content.Among them,the moisture content increases from 13.0% to 21.2%,and the interfacial cohesion decreases by 36.4%.(2)With the increase of water content,the interfacial cohesion,internal friction angle,interfacial friction coefficient and equivalent shear stiffness decrease.When the water content increases from 13.0% to 21.2%,the interfacial cohesion decreases by 33%.(3)Under the same water content,with the increase of root soil area ratio,the interface cohesion,interface friction coefficient and equivalent shear stiffness of root reinforced eco bag increase.The root soil area ratio increased from 0.008% to 0.027%,and the interfacial cohesion increased by 61%.(4)Through the shear tests on the interface between eco bag and bare soil and the interface between eco bag and soil reinforced by roots under different water content,it is concluded that the interface cohesion of eco bag and soil reinforced by roots is greater than that of eco bag and bare soil under the same water content.When the moisture content increased from 13.0% to 21.2%,the interfacial cohesion between root reinforced eco bag and bare soil increased by 29.2% and 40.5% respectively.(5)By fitting the stress-strain relationship of indoor direct shear test,the relationship between shear stress and displacement of eco bag and soil interface conforms to Clough-Duncan hyperbolic model.Through the analysis of the model parameters,it is concluded that:(1)The damage ratio of eco bag and bare soil is between 0.65 and 0.89,the moisture content increases from 13.0% to 21.2%,and the stiffness coefficient K of eco bag and bare soil decreases by 0.06 and 4.8%.(2)The damage ratio of eco bag and soil reinforced by root system is between 0.77 and 0.94,which indicates that the damage ratio of eco bag and soil reinforced by root system can be increased.When the water content increased from 13.0% to 21.2%,the stiffness coefficient K of root reinforced eco bag and soil decreased by 0.76,with a decrease of 42.2%.(3)Under the same water content,with the increase of root soil area ratio,the damage ratio of root reinforced eco bag to soil ranged from 0.73 to 0.95,the root soil area ratio increased from 0.008% to 0.027%,and the stiffness coefficient K increased by 0.62 to 52.5%.(6)Through the shear test of eco bag soil interface and summarizing the previous research results,it is found that,the relationship equations between initial shear stiffness,ultimate shear stress and normal stress in hyperbolic model are simplified,then,two variables,water content and root soil area ratio,are introduced to establish a hyperbolic constitutive model considering normal stress and water content and normal stress and root soil area ratio.Finally,the hyperbolic model fitting results were compared with the experimental data,and it was found that the two factors had a good correlation,indicating that the two factors coupling interface constitutive model could fit relationship between shear stress and shear displacement of interface between tall fescue reinforced eco bag and soil. |
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