Effect Of Overhaul Scheme On Reflective Crack Propagation Of Asphalt Pavement

With the increase of traffic volume,the increase of heavy-duty vehicles,and the influence of temperature,humidity and other factors,a large number of roads built in the early days of our country began to be damaged to varying degrees.Overhaul and maintenance of severely damaged roads will be a major trend in road development in the future.However,the most common disease in pavement damage is pavement cracking.Therefore,it is of great significance to study the influence of various factors on crack propagation and fatigue life of asphalt pavement in the selection of overhaul scheme for the design and scheme selection of highway pavement structural rehabilitation in China.Based on the overhaul project of Xupingnan section in Lankao-Nanyang Express,this thesis analyzes and investigates the main crack cracking forms.Combined with relevant design schemes,ABAQUS finite element software is used to simulate and analyze the expansion of reflection cracks.The research contents are as follows: Firstly,the temperature field model of pavement structure is established to analyze the expansion of reflective cracks under the action of temperature alone,and the influence of various factors on the expansion of reflective cracks in the selection of overhaul scheme is studied.Secondly,the vehicle moving load is added to the original model to analyze the expansion of reflective cracks under the combined action of temperature and moving load,and to study the influence of various factors on the expansion of reflective cracks.Then,based on Paris crack fatigue model,the influence of various factors on asphalt pavement crack fatigue life is studied.The correlation degree between different factors and fatigue life of cracks is compared and analyzed by using grey correlation degree analysis method.Finally,according to the BP neural network theory,the fatigue life prediction models of asphalt pavement cracks in the milling upper layer and the milling middle layer are established respectively,and their accuracy is verified.The results show that:(1)The cracks under the single action of temperature are tensile cracks,while the cracks under the joint action of temperature and moving load are composite cracks with the coexistence of tensile and shear types.(2)Different layers of crack propagation will have different effects on crack propagation due to the material characteristics of back paving and additional paving after pavement milling.Increasing the thickness of overlays and laying interlayer materials can inhibit the crack propagation,among which geogrids with large modulus have better effect on inhibiting tensile cracks,while anti-crack patches with small modulus have better effect on inhibiting shear cracks.(3)Decreasing the modulus and linear expansion coefficient of milling and resurfacing materials,increasing the thickness of resurfacing layer and setting interlayer materials can prolong the fatigue life of cracks.When milling the middle and upper layers,the correlation degree of each factor with crack fatigue life is as follows: middle layer modulus(0.7868)> middle layer linear expansion coefficient(0.7688)> overlay layer thickness(0.7549)> upper layer linear expansion coefficient(0.7208)> overlay layer linear expansion coefficient(0.7191)> upper layer modulus(0.7105)> overlay layer modulus(0.6952).When milling only the upper layer,the correlation degree of each factor with crack fatigue life is as follows: overlay layer thickness(0.8658)> upper layer modulus(0.8313)> overlay layer linear expansion coefficient(0.8297)> overlay layer modulus(0.8255)> upper layer linear expansion coefficient(0.8204).(4)The fatigue life prediction model established by BP neural network has high prediction accuracy.Through substitution test,the relative errors of the prediction model are all within 3%.In this thesis,the influence of various factors in the overhaul plan on the propagation of reflection cracks is studied,and a crack fatigue life prediction model is established.The conclusions and results obtained can provide a theoretical basis for the selection of pavement structural rehabilitation plan.