Evaluation Model For Fracture Performance Of Matrix Asphalt Under Low Temperature Tension Based On Energy Balance Principle

Nowadays,cracking of asphalt pavement has become one of the main diseases in road engineering.Whether in frozen or non-frozen areas,cracking phenomena will occur to varying degrees.An important reason for cracking of asphalt pavement is brittle fracture of asphalt at low temperature.In engineering,the fracture parameters of asphalt materials are usually determined by fracture performance test,so as to evaluate their fracture properties.However,this method is more complex in the fabrication of specimens and the calculation of fracture parameters,and the measurement accuracy is greatly affected by the size of specimens.With the rapid development of surface science,related scholars have found that the surface energy of asphalt materials is related to its cracking phenomenon:asphalt will produce new surface in the cracking process,thus releasing surface energy.At the same time,the surface energy measurement technology is simple and the measurement accuracy is high.Therefore,it has certain scientific research value to evaluate the fracture properties of asphalt materials by surface energy theory.Based on the principle of energy balance,this paper establishes a fracture evaluation model of matrix asphalt under low temperature tension by means of the complex function method of elasticity,in order to explore the relationship between surface energy and fracture performance of matrix asphalt under low temperature tension.The specific work is as follows.Based on the principle of energy balance and some reasonable assumptions,the mathematical model of asphalt cracking is established.The displacement field on the inner surface of an infinite plate hole with an elliptic hole is solved by means of the complex function method of elasticity.By approaching the elliptical hole to the crack,the displacement field of the inner surface of an infinite plate hole with a central penetrating crack is obtained.The critical condition of asphalt cracking is further solved,that is,the energy release rate of the system is equal to twice the surface energy of matrix asphalt.Based on the relationship between stress intensity factor and energy release rate,the critical condition of asphalt cracking under the condition of limited plate width is solved by introducing the factor of plate width,which provides a theoretical basis for experimental verification.According to the deduction results of the theoretical model,the tensile test of matrix asphalt with central penetrating crack is designed,and the values of parameters?F/?BW??²/?and1/tan??a?are obtained.The linear regression of the two parameters is carried out to obtain the determinant coefficient R²,which verifies the accuracy and rationality of the theoretical model.The final results show that the surface energy of asphalt can qualitatively characterize its fracture properties.According to the deduction results of the theoretical model,the critical cracking condition of matrix asphalt without macro cracks is conjectured,that is,there is a linear relationship between the ultimate tensile stress?and parameter ?2E?_s/??^1/2.By designing the tensile test of matrix asphalt without macro cracks,the values of ultimate tensile stress?and parameter ?2E?_s/??^1/2 are obtained,and the linear fitting of the two values verifies the reasonableness of the conjecture.The final results show that the fracture properties of asphalt are related to surface energy and elastic modulus without macro cracks.Fracture properties can not be independently characterized by surface energy.In order to simulate the fatigue cracking process of pavement structure and get the fatigue life of pavement structure,the critical condition of asphalt cracking obtained by theoretical model is introduced into the numerical simulation of pavement fatigue life,and the variation rule of pavement fatigue life with pavement material parameters is studied after introducing the critical condition of asphalt cracking.