Evaluation Index Selection And Cracking Process Simulation Of Asphalt Mixture Based On SCB Test

Cracking is one of the diseases of asphalt pavement,which seriously affects driving safety.It is of great significance to study the crack resistance of asphalt mixture for the prevention and treatment of pavement cracking.In order to explore the problem of pavement cracking,researchers have proposed test methods such as semi-circular bending test(SCB)to evaluate the crack resistance of asphalt mixture and crack resistance evaluation indexes such as fracture energy.Due to the complexity of the internal structure of asphalt mixture,different indexes have different analysis angles and emphases on crack resistance.Therefore,it is necessary to explore the influence of different factors on the evaluation index and improve the index to obtain better evaluation results.In addition,the numerical simulation method can be used to deeply understand the cracking mechanism of materials,explore the law of crack propagation and damage,and provide a theoretical basis for preventing cracking.In this thesis,SCB tests at different temperatures and loading rates are carried out to obtain P-LLD and P-CMOD curves and corresponding evaluation index values.The multi-index variation rules of the two curves are compared and analyzed to verify whether the evaluation index values can distinguish the crack resistance of different asphalt mixtures.The test shows that the two curves can effectively reflect the change rule of the crack resistance of asphalt mixture affected by different factors,but the change range of P-LLD curve index is small,it is difficult to distinguish different asphalt mixtures,and it is not sensitive to curve parameters,P-CMOD curve is more suitable for application in SCB test.Secondly,the six fracture performance evaluation indexes of fracture energy,flexibility index,crack resistance index,fracture strain capacity limit,toughness index and Nflex Factor are analyzed,and the influence of temperature,loading rate and RAP content on the crack resistance and index evaluation effect of asphalt mixture is explored.Through qualitative and quantitative analysis,the influence degree of these three factors on crack resistance and evaluation index is obtained.Based on the analysis of each index,the weight of different indexes is obtained by analytic hierarchy process,and the weight of each index is calculated.The comprehensive evaluation index of crack resistance of asphalt mixture is put forward and verified.The results show that the comprehensive evaluation index can distinguish the crack resistance of different asphalt mixtures,and can obtain the change rule of the crack resistance of asphalt mixture affected by various factors.Finally,the bilinear cohesion model is introduced,and Abaqus is used to simulate the whole cracking process of asphalt mixture SCB specimens at 1°C and 50mm/min.The numerical simulation results based on the bilinear cohesion model are in good agreement with the indoor test results,which verifies the validity of the model to simulate the cracking.The results of numerical simulation reveal the cracking mechanism of asphalt mixture.The change of stress cloud diagram reflects that the cracking of asphalt mixture is divided into five stages : initial loading,specimen damage,crack generation,crack propagation and complete failure.