Study On The Effect Of Particle Size On The Interface Friction Between Geogrid Reinforcement And Soil

With the continuous development of China's economy,reinforced earth technology has been widely used in all kinds of civil engineering construction.Geogrids,as one of the main reinforcing materials,have the advantages of high tensile strength,small creep and adaptability to all kinds of soil environments,so they are widely used in reinforced soil structures.At present,the study of interface friction characteristics of geogrid-reinforced soil is also one of the hot topics in civil engineering research.Although scholars at home and abroad have done a lot of research work on the reinforcement mechanism of the reinforced soil interface,there are many factors that can affect the characteristics of the reinforced soil interface.The reinforcement mechanism is very complex,especially in the field of reinforced soil.The fillers of the ribs are different,especially the current research on fillers is still lacking.Based on the pull-out test and discrete element simulation,this paper studies the friction characteristics of the interfacial friction between the two-way stretched plastic geogrid in fillers with different particle sizes.The main research contents and results are as follows:(1)The tensile test of geogrid is carried out to determine the parameters during numerical simulation;The geotechnical test of gravel,standard sand and silt was carried out,and the test analysis of different interface of reinforcement soil was carried out.(2)Under vertical static load,pull-out tests are carried out in different fillers to analyze the influence of different vertical stresses and different pull-out rates on the friction characteristics of the interface between reinforcement and soil.The greater the vertical stress,the greater the maximum pull-out force.The effect of drawing rate is not obvious.But in general,the greater the drawing rate,the greater the maximum drawing force;The influence of different embedded lengths and different numbers of transverse ribs on the pull-out force is analyzed.The inserting force of the grid transverse ribs to the filler plays a major role in the drawing force.The surface friction of the longitudinal ribs plays a role in the early stage of drawing,while the transverse ribs play a tensile effect in the middle and late stages.Finally,the filler is used as a variable to analyze the influence of particle size on the friction characteristics of the interface between reinforcement and soil.The larger the particle size,the more irregular the surface of the particle,and the greater the fixing force with the grid mesh,which in turn increases the drawing force.Under the action of vertical dynamic load,pull-out tests with different load frequencies and amplitudes are carried out.The result showed that maximum pulling force increases with the increase of the load frequency,and the amplitude of its increase increases with the increase of the amplitude.(3)Using PFC2 D discrete element software for numerical simulation.First,the direct shear test model of the packing and the tensile test model of the grid were established.The results of the indoor direct shear test and tensile test were calibrated to make the indoor test curve and simulation curve fit each other.After determining the available parameters,the drawing test model was established.The stress-strain analysis rule results obtained by the simulation are consistent with the indoor pull-out test,indicating that the numerical simulation can more accurately simulate the pull-out process of the reinforcement and soil,and the simulation test results are feasible.Analyzing the meso-parameters,including displacement field,porosity,coordination number,contact force chain,etc.,shows the evolution of particle motion and force chain from a meso-level perspective.The distribution of contact force determines the macroscopic mechanical properties of the specimen.The influence of the pull-out test results is visually demonstrated by the meso-parameters such as coordination number and porosity,the rotation of soil particles inside the sample and the distribution of contact force between gravel particles.In the process of drawing,the direction of contact chains between particles is consistent with the direction of drawing,and with the increase of drawing displacement,the contact force chains become denser and thicker.For the same kind of filler,the particle-to-pore ratio between the particle size and the grid mesh size is determined,and it is found that as the particle-to-pore ratio increases,the cohesive force and internal friction angle between the reinforcement and the soil increase.