Study On Pull-out Test And Numerical Simulation Of Reinfored Earth

The reinforcement technology has been widely used and is playing an increasingly important role in railway,port,construction and other engineering fields since the introduction in 1960's.The soil-reinforcement interface characteristics are the most important parameter indexes in the design and construction of reinforced structure,and also the foundation of studying its working behavior and failure mode.There are many factors that affect the interface interaction between the reinforcement and soil,and the reinforcement mechanism is complex.As a result,the existing research lags behind the engineering practice,and the results cannot fully explain the complex problems in the reinforced earth engineering,which needs to be explored continuously.Based on the pull-out tests,this paper analyzes the influence of the tie bar's length,overburden load and relative compactness on the ultimate pulling resistance through theoretical analysis and numerical simulation,and studies the distribution law of the tie bar's tension and shear stress during the drawing process,as well as the development law of horizontal displacement and stress of the filling.By summarizing and analyzing the results,the following conclusions are obtained:(1)Under the condition of low overburden load,the failure generally presents as progressive failure similar to ductility,while under the condition of high overburden load,a sudden pulling failure similar to brittle will occur.The interfacial friction angle decreases with the increase of the tie bar's length or the overburden load,and increases with the increase of the relative compactness;(2)The frictional resistance at the interface between the reinforcement and soil near the slit is first generated.With the increase of the horizontal load,the shear stress and tension gradually developed to a deeper depth until it is transmitted to the entire length,and the value became larger and larger.The smaller the stiffness of the reinforcement and the rougher the interface between the reinforcement and soil,the more obvious the exponential relationship;(3)The closer to the position of the tie bar,the greater the horizontal displacement of the filling,and tends to be decrease waving down from the center.The stress concentration occurred at the position of the slit,so the horizontal stress is the largest,and the horizontal stress near the end of the reinforcement is the smallest.The overall shear stress decreases gradually from the drawing end to the free end,showing a non-linear relationship.The change rule is consistent with the result of theoretical calculation;(4)There is little difference between the numerical simulation results conducted by means of the stress-controlled tests and the strain-controlled tests.When the drawing displacement is small,the scheme without reserved length is recommended;when the drawing displacement is large,the scheme with reserved length is recommended.It is recommended to set the reinforcement in the middle of the model box,and the thickness of the upper and lower filling shall be at least 30 cm.