Research On The Mechanical Effects Of The Reinforced Soil Interface Based On The Shear Band Theory

With the development of Chinese economy,the construction of highways and railways has developed rapidly.The treatment of roadbed and foundation is the key to road and railway construction,so the safety and stability of the foundation is particularly important.Reinforced soil technology has been widely used by industry insiders due to its advantages in dealing with the settlement of soft soil foundations.With the development of science and technology,the technology of reinfofrced soil has become more and more mature,however,the mechanical properties of the interface between reinforced soil and reinforced soil structures is still a difficult problem.Therefore,this paper theoretically and numerically analyzes the mechanical properties of the reinforced soil interface in reinforced soil structures,and studies the mechanical properties and reinforcement mechanism of geogrids.This paper calculates the peak pulling force at the reinforced soil interface within the elastic range,proposes an expression for the peak pulling force at the reinforced soil interface,and analyzes its influencing factors.Finally,finite element numerical simulation software was used to study the deformation behavior of soil particle layer in contact with the interface.The research contents and results are as follows:(1)The most important mechanical index of geogrids is tensile strength.When the test temperature is too low or the pulling rate is too high,the relationship curve between tensile force and elongation is almost linear.Creep,as the main influencing factor affecting the service life of geogrids,is an attenuated creep mode at low stress ratios(20%,40%),and undergoes stages:primary creep and secondary attenuated creep;At high stress ratios(60%,80%),it is a non decaying creep mode that undergoes stages: primary deceleration creep,secondary constant velocity creep,and tertiary loading creep.The reinforcement mechanism between reinforced soil interfaces(frictional reinforcement theory,quasi cohesive force Morh Coulomb theory,tensile membrane theory,equivalent confining pressure theory of reinforcement,constrained reinforcement theory,shear band theory)is studied through two research methods: restricting lateral deformation of soil mass and restricting sliding displacement of soil mass.Based on the basic mechanical elements,a multi element parametric model is established to simulate the viscoelastic plastic mechanical properties of geogrids at different stages.(2)Based on the existing theoretical research on the reinforced soil interface,a formula for the peak pullout force at the reinforced soil interface is proposed,which predicts the tensile force and displacement at each position of the reinforcement when the tensile force does not exceed its peak pulling force,thereby determining the maximum peak pulling force.The effects of effective reinforcement length and shear stiffness on reinforcement displacement and their variation rules were investigated within the range of not exceeding the maximum peak tensile force.The results show that when the peak pulling force is constant,the effective reinforcement length and shear stiffness of the reinforcement have a significant impact on the peak pulling force,while the elastic modulus has a relatively small impact on the peak pulling force.The displacement of reinforcement decreases nonlinearly with the increase of effective reinforcement length and shear stiffness.Comparing the calculated results of the formula for peak tensile force at the reinforced soil interface with the test results of the tensile test,the results were in good agreement.Based on the effective reinforcement length formula,the length of reinforcement in the finite element model of the reinforcement soil interface is determined.(3)In this chapter,finite element numerical simulation software is used to mechanically analyze the shear localization behavior of the reinforcement-soil interface.The influence of the movement of soil particles along the interface boundary structure on the evolution and location of shear band is analyzed and compared with the numerical simulation results that limit the maximum displacement.Through analysis,it can be seen that the displacement increases linearly with the increase of height,and the displacement of soil particles also increases with the increase of the overall structural displacement,but the particle layer located outside the shear band does not generate displacement.The stress and strain show the same trend of first increasing and then decreasing with the increase of height,with a parabolic curve shape and reaching a peak value at about h=3cm.The equivalent compressive stress shows a trend of decreasing first and then increasing with the increase of height,and reaches the minimum value when the height is about3 cm.The location of the shear band is located near the bottom surface of the structure,and the analysis shows that there is no significant correlation between the thickness of the shear band and the magnitude of the structural displacement.