Damage Characteristics And Numerical Simulation Analysis Of Cement-stabilized Macadam Base In Seasonal Frozen Regions

Cement-stabilized macadam base material is widely used in highway structure in China.In seasonally frozen regions,with the surge of vehicle load and the changeable natural environment,road damage often occurs.In the actual service process,the material damage and structure damage of cement stabilized macadam base will occur,which will affect the service life of road structure.The main reason is that it is difficult to fully analyze the influence of load-freezing-thawing coupling on cement-stabilized macadam base material in road structure design,so it is impossible to accurately evaluate the structural damage.Therefore,it is necessary to study the influence of freezing-thawing damage on material life and the change rule of mechanical properties of cement-stabilized gravel base material under the coupling action of load-freezing-thawing.In this paper,a large number of laboratory tests were carried out in combination with jilin Provincial Transportation science and Technology project "Key Technology Research on design and Construction of cement stabilized base in seasonal Freezing Zone".Explores the cement stabilized gravel base materials freeze-thaw damage and fatigue damage characteristics,and design the coupling damage test,through material under the action of the load-freeze-thaw coupling modulus attenuation law research,construct damage modulus forecast model,which is scientific and reasonable evaluation of cement stabilized gravel base materials damage characteristics in seasonal frozen soil region to provide theoretical basis and reference.In this paper,unconfined compressive strength,flexural tensile strength and flexural rebound modulus are used as evaluation indexes.According to the results of laboratory tests,the variation rule of material properties of cement-stabilized gravel after a certain number of freezing-thawing cycles is explored.The results show that the unconfined compressive strength,flexural strength and flexural rebound modulus all decrease with the increase of the number of freezing-thawing cycles,and the flexural rebound modulus decreases the most.Under the effect of freeze-thaw cycle,the cement stabilized macadam base material with cement content of 7.0% has the best mechanical properties and frost resistance.After 15freezing-thawing cycles,the flexural modulus loss rate of cement-stabilized macadam tends to be stable.It is suggested to use the flexural modulus loss rate of 15 freezing-thawing cycles in the evaluation of freezing-thawing resistance of cement-stabilized macadam base material.Based on the fatigue test results of cement stabilized gravel base material,the fatigue equation of base material under 0,5,10 and 15 freezing-thawing cycles was obtained in this paper,and the influence of freezing-thawing cycles on the fatigue life of base material was explored.The results show that under the same stress level,with the increase of the number of freezing-thawing cycles,the fatigue life of cement-stabilized gravel specimens decreases more and the percentage of residual fatigue life decreases.Based on the existing studies on fatigue performance,a load-freezing-thawing coupling damage model of base materials was proposed in this paper,which took the elastic modulus of flexural tension as the parameter.On this basis,the coupling damage test scheme was formulated,and the coupling action unit was designed with the unit of years.According to the modulus attenuation law under different years,the modulus prediction equation of cement-stabilized macadamia base material under coupling damage was established.It provides reference for the value of modulus design parameters of cement stabilized macadamia base in road design.Based on ANSYS finite element analysis software and combined with the test road project,a three-dimensional solid model of road structure was established to analyze the mechanical response law of cement stabilized macadam base structure under the coupling action of freezing-thawing and load.The results show that under the action of moving load,the vertical dynamic stress and displacement at the bottom of each structure layer decrease gradually along the road structure layer.With the increase of coupling elements,the vertical strain at the bottom of the surface layer does not change obviously,but the vertical strain at the base layer is significantly affected.With the increase of coupling elements,the stress at the bottom of the base layer decreases gradually,while the strain increases.