Experimental Study On Mechanical Properties Of Reinforced Soil Interface And Numerical Simulation Of Particle Flow

In accordance with the major development strategy determined by the State and Shandong Province's “13th Five-Year Plan” for scientific and technological innovation and development.The coastal area of Qingdao has become a global marine science and technology innovation center and a two-way integration into the “One Belt and One Road” pilot zone.Therefore,the transportation infrastructure investment is enormous,and the subway,the high-speed rail and expressway projects are here,the long-term service performance,slope deformation behavior characteristics,evolution mode and stability of the subgrade embankment project under traffic load have become the focus of attention.The application of geosynthetics reinforcement technology to the embankment slope project can effectively solve the key problems of the embankment service period:(1)post-construction settlement problem,especially differential settlement problem;(2)long-term stability problem.It is very important to study the interface characteristics of reinforced cushion under traffic load for solving the key problems of embankment service life.Because of the complicated interaction mechanism between reinforced soil and soil in reinforced soil engineering,research on reinforced soil theory and design parameters still lags behind the wide application of reinforced soil technology.There are many factors affecting the mechanical properties of the reinforced soil interface.The method of experimentally studying the interface characteristics of reinforced soil is not perfect.Based on the study of the mechanical properties of the geosynthetic interface between different geosynthetics and different soils,this paper has theoretical and practical significance for improving the design theory of reinforced soil and promoting the application of reinforced soil technology.In this paper,the mechanical properties of the interface between geosynthetics and sand are studied.Based on the research mechanism of the reinforced soil engineering,the sensor testing technology is adopted by conducting large-scale direct shear test in the room.Using Xiamen Eso standard sand to arrange sand with different particle gradation.Consider different direct shear interfaces: 1)no reinforced interface;2)grid reinforced soil interface;3)geotextile reinforced soil interface.Three factors affecting the mechanical properties of reinforced soil interface(types of geosynthetics,sand grains with different particle sizes and different normal stresses)are analyzed.In order to supplement the macroscopic physical test results,through the particle flow numerical simulation software PFC2 D,the direct shear test of the soil suitable for the actual test is established,and the motion law of the particles during the direct shear process is obtained from the mesoscopic point of view,and the relevant influencing factors are obtained,and verify the consistency with the test.The main research contents and conclusions of this paper are as follows:(1)Through the large direct shear test at the interface of the reinforced soil,when the normal stress is low(50 kPa),the effect of the geotextile on the reinforcement of the fine sand is more significant than that of the coarse sand,and the reinforcement effect of the geogrid on the coarse sand than the effect of fine sand is more significant;When the normal stress is large(110 kPa),the influence of different ribs on the strength of the reinforced soil interface is reduced.When the normal stress is low(50kPa),the particle size of the filler has little effect on the mechanical properties of the interface between the reinforcement and the soil;when the normal stress is large(110kPa),The effect of non-graded sand and geosynthetics is better,the diameter size has little effect on the mechanical properties of the reinforced soil interface.(2)When the normal stress is low(50kPa),the required shearing displacement is shorter when the peak intensity is reached.When the normal stress is large(110kPa),the shear displacement is longer when the peak intensity is reached.The dilatancy decreases as the normal stress increases.Geosynthetics can exert their reinforcing effect when the normal stress is large(110kPa).(3)The shear strength of the reinforced soil interface obtained according to the test results is fitted,and the internal friction angle of the shear strength of the reinforced soil interface is within 4°.The geosynthetics category has little effect on the internal friction angle of the reinforced soil interface.The geogrid provides a “cohesion” to the geosynthetic interface that is larger than the geotextile.(4)Using the PFC2D particle flow numerical simulation software to establish a direct shear model of the reinforced soil interface.Operational calculation of sand-soil and different normal stress-bearing interface direct shear models of different particle sizes by fish language.In the process of direct shearing,the direction of contact between the particles is consistent with the direct shear direction,and as the direct shear displacement increases,the contact force chain is more encrypted and coarsened.The stress-strain analysis law obtained by direct shearing is consistent with the physical test,which indicates that the numerical simulation can accurately simulate the direct shear process of the soil,and the simulated test results are feasible.The research results can provide theoretical support for the application of reinforced soil technology in transportation infrastructure engineering.By establishing a suitable numerical calculation model,it is beneficial to promote the construction method of high-precision and high-efficiency numerical model of reinforced soil engineering,and at the same time save economic cost.