| The highway traffic of China has always been in a rapid development tendency,reflection crack is one of the main diseases of semi-rigid base asphalt pavement and the repaved asphalt layer of old road,setting a stress absorbing layer between the semi-rigid base and asphalt surface layer or the repaved asphalt layer and the old road is an effective widely adopted measure to prevent the reflection cracks.As the interlayer of pavement structure layer,the material performance of Asphalt Rubber-Stress Absorbing Membranes Interlayer(AR-SAMI)is the key to prevent reflection crack.On the basis of previous studies,this paper continues to make further study about the mechanism,anti-cracking ability and mechanical property of AR-SAMI,mainly include the following five aspects.The research works of the first aspect include direct compression,shear and tensile three basic mechanical property tests for the rubber asphalt material,for the purpose of evaluating the mechanical properties of rubber asphalt mixture.The test results show that the compression,shear,tensile strength of rubber asphalt material is negatively correlated with the temperature and positively correlated with the loading rate,which also provide mechanical parameters for the establishment of finite element model of road;the purpose of interface tension and interface shear tests of asphalt rubber materials is to analyze the mechanical properties of rubber asphalt and concrete interface,but also provide parameters for the establishment of finite element model of road.The research works of the second aspect include the semi-circular stretch bending test of rubber asphalt material,applying J integral theory to evaluate its anti-cracking performance,to calculate the fracture toughness Jc of material under different temperatures and loading rates by fitting the experimental data,analysis of crack resistance of asphalt rubber materials and provide reliability reference for the SCB numerical simulation analysis.A semi-circular finite element model of rubber asphalt material is established,and the influence of elastic modulus and temperature change on crack resistance of material is analyzed and compared with the experimental results.The research results show that J integral theory can effectively evaluate the crack resistance of rubber asphalt materials,and the fracture toughness Jc of test specimen decreases with the increase of temperature,and decreases with the deepening of precut kerf.The research works of the third aspect include the analysis of fatigue damage characteristics of asphalt rubber material,small beam fatigue test of asphalt rubber material is implemented,analysis of different factors on fatigue life,and build the multi-factor damage model and damage evolution equation,to obtain the constitutive equation of fatigue damage,the constitutive equation can well describe the mechanical behavior of the asphalt mixture under cyclic loading and compare with the test data.The research results show that linear function can well describe the relationship of logarithmic fatigue life and test conditions of the fatigue test specimen,using the elastic-power reinforced model to build fatigue damage constitutive equation for small beam test specimen under the elastic and elastoplastic condition,and to provide a theoretical basis for the research work of road fatigue damage.The research works of the fourth aspect include fatigue crack growth and crack control analysis after repaving AR-SAMI on the old cement concrete pavement,the composite small beam fatigue test is implemented.The test adopts three kinds of prefabricated cement concrete through crack and are respectively repaved with AR-SAMI and ordinary asphalt composite small beam to carry out fatigue crack growth test,and compare and analyze the stretched form and fatigue life of fatigue crack of the overlay under two kinds of structure,and then analyze the crack resistance of AR-SAMI.Build finite element model for the rubber asphalt composite small beam,to simulate the fracture expansion process of the base layer under different forms of cracks.At the same time,compare the force-deformation curve with the test to verify the correctness of the test.Through the experiment,it is found that the order of fatigue life for all kinds of overlay is:diagonal crack>partial crack>medium crack,and found that the fatigue life of composite small beam paved with AR-SAMI is 2.01,1.87 and 1.72 times than the composite small beam without AR-SAMI under three kinds of cracks,it can be seen that the pavement of AR-SAMI can effectively prolong the service life of the pavement.The research works of the fourth aspect include establishment of Coulomb friction contact and cohesive contact finite element model of road,to analyze the corresponding mechanics,by changing the elastic modulus,thickness,the friction coefficient of AR-SAMI of the finite element model to analyze the influence of different factors on the performance of AR-SAMI,and analyze the influence of base crack length on the stress at the top of crack,and put forward the reasonable pavement thickness of AR-SAMI.The research results show that after paving AR-SAMI,the stress intensity factor KI decreases by 47%,and AR-SAMI is found to be effective in inhibiting the generation of reflection crack.After summarizing,it is found that the reasonable pavement thickness of AR-SAMI is 2.5 cm. |
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