Study On Crack Resistance And Material Adaptability Based On Extended Finite Element Method For Crack Resistant Fiber Seal

At present,semi-rigid base has been widely used as the load-bearing layer in the structural design of high-grade asphalt pavement in our country,but the semi-rigid base has poor anti deformation ability and is easy to crack,and finally reflects to the surface layer,causing the pavement cracking.In order to solve the problem of reflective cracking on semi-rigid base of asphalt pavement,scholars at home and abroad have proposed that the use of crack resistant fiber seal as a stress absorbing layer between semi-rigid base and surface layer has been widely applied.The anti-cracking fiber seal has the advantages of good cracking resistance,strong stress absorption and diffusion,high stability and quick construction.At present,most of the researches on crack resistant fiber seal are mainly focused on process introduction.The amount of material is basically determined by empirical method,which lacks theoretical guidance and has great randomness in construction.Therefore,it is of great theoretical and practical significance to study the crack resistance effect of the crack resistant fiber seal and to seek semi empirical and semi theoretical method for the design of crack resistant fiber seal.First,based on the theory of fracture mechanics,this paper uses the extended finite element method to simulate the advantages of crack propagation.The asphalt pavement structure of typical expressway is established by ABAQUS finite element software.The crack resistance effect and its influencing factors of crack resistant fiber seal layer under asphalt pavement structure under dynamic load are studied.The numerical simulation analysis shows that the expansion process of load reflective cracks on semi rigid base asphalt pavement can be divided into four stages: damage stage,initiation stage,stabilization stage and acceleration stage.The stress intensity factor of the asphalt pavement structure is greatly influenced by the modulus of the crack resistant fiber seal.The stress intensity factor of the asphalt pavement structure is greatly influenced by the modulus of the crack resistant fiber seal.The modulus of stress intensity factor increases with the modulus of the sealing layer when the modulus of the crack resistant fiber seal is greater than 300 MPa.Through the analysis of the crack resistance effect of the crack resistant fiber seal under the most unfavorable combination condition,the applicable condition of the anti-crack seal layer is obtained: axle load should not be larger than0.8MPa,and the crack width of the base layer should not exceed 2mm.It is recommended that the modulus of the crack resistant fiber seal is 200MPa~300MPa.Based on the micro-mechanics theory of composite materials,the method of the analysis of the equivalent modulus of the fissure fiber sealing layer is discussed.The equivalent modulus formula of fiber reinforced composite is applied to calculate the equivalent modulus of the crack resistant fiber seal at 20 C at different volume of fiber.The error of the calculated value is analyzed through the tensile test results.From the volume and temperature of the fiber,the cause of the error is analyzed.It is found that the temperature is the main factor when the volume of the fiber is less than 2%.According to the result of the error analysis,the formula of the equivalent modulus of the crack resistant fiber seal with the effect of temperature is considered when the volume of fiber volume is less than 2%.The elastic modulus of the crack resistant fiber seal is calculated by the modified formula,which is in good agreement with the test value.This paper summarizes the engineering application experience of fiber lithotripsy seal at home and abroad,and establishes the experience design method of crack resistant fiber sealing layer.Combined with theoretical research,a semi empirical and semi theoretical method for the design of crack resistant fiber seal is put forward.First,by extending the finite element numerical simulation analysis,the applicable working condition of the crack resistant fiber seal layer is obtained,and the elastic modulus value is recommended.Then,the experiential method is used to select the dosage of anti-cracking fiber seal material,and the modified equivalent modulus formula is used to calculate the elastic modulus of the crack resistant fiber seal.Finally,verify whether the modulus is in the recommended modulus range of the extended finite element numerical simulation,compare the material and determine the material consumption.