The Study Of Shear Characteristics Of Geogrid-soil Interface

In recent years,a large number of geosynthetics gradually become the reinforced materials,because of its superiority and economical efficiency.With the development of the economy,the reinforced soil has been widely used in engineering practicals,such as retaining wall,slope,soft ground and abutment.One of the most important factors that affect the stability of geosynthetics is the interfacial mechanical properties.In this paper,experiments,numerical analysis and theoretical analysis are used to study the mechanical properties of geogrid-soil interface in terms of the influencing factors,the numerical simulation research,mechanism research,ect.In the same way,the soil-geogrid interface mechanism is discussed.In this paper,a series of researches work are carried out,and several useful conclusions are obtained as follows:(1)By conducting the monotonic shear test of geogrid-soil interface,the interfacial friction characteristics and dilatancy of geogird-soil interface under different conditions were investigated,including normal pressure,shear rate,geogrid types and so on.The experimental results show that the influencing factors can not be neglected in interfacial shear strength and dilatancy,which will be helpful to study the interface mechanism between the geogrid and soil.(2)The cyclic shear test and cyclic monotonic shear test between geogrid and soil are carried out to investigate the interfacial characteristics under dynamic conditions.The effects of normal pressure,cycle number and shear displacement amplitude on the dynamic characteristics were investigated,including the comparsion between monotonic shear test results and the cyclic test results.The test results show that interface shear strength will be improved after cyclic shear tests,but the shear displacement amplitude has a little effect on the interface shear strength.The interfacial shear strength increases with the number of cycles,while the shear strength will not increased when the cyclic numbers reach seven times.(3)Based on finite element analysis software,a reasonable model of direct shear test and pull-out test was established respectively.Reasonable numerical parameters are selected by experimental results,and two kinds of tests are simulated respectively to verify the feasibility of the paremerers used in the numerical simulation.The influence of parameters,such as soil parameters,geogrid axial stiffness and reinforced length,on the interface characteristics between geogrid and soil are studied.Finally,the development of interface friction will be discussed under two kinds of experimental conditions respectively.(4)The mechanical properties of the interface under the pull out test are investigated by theoretical analysis.Based on the load displacement curve of the pull out test,the elastic-exponential model and elastic-plastic model are established for the normal condition and softening condition respectively,which also taking the progressive failure characteristics in the pull out process of the geogrid-soil interface into account.The existing model is validated by the previous test results,and the stress transfer and distribution law of the pull out process are studied in detail at last.The factors influencing the value and distribution trend of the interface friction are analyzed,which mainly includes the elastic modulus,the length of the reinforcement,the exponential softening factor,the residual length,the shear stiffness and so on.