Numerical Modeling Of Moisture Damage Due To Pore Pressure In Asphalt Pavement Using Theory Of Fatigue Damage Mechanics

Asphalt pavement water damage refers to the gradual decrease of the strength of the saturated pavement under the combined effect of vehicle load and pore water pressure,and the asphalt mixture tends to loosen,which eventually results in a network crack,looseness and pits.Water damage seriously affects the performance of the pavement and reduces its service life.It is one of the common diseases in the service process of asphalt pavement.Studying the mechanical mechanism of asphalt pavement water damage,analyzing its evaluation methods and prevention measures have always been important topics in the field of road engineering.According to the existing results,when the pavement is saturated with water,the excessive pore water pressure generated by the dynamic vehicle load will cause the strength of the asphalt mixture to decay rapidly,which is the main mechanical inducement of water damage to the asphalt pavement.However,in the current research on the numerical spatial distribution of pore water pressure,whether it is measured values,analytical solutions or numerical solutions,the results generally have a large dispersion,so the size,distribution and The main influencing factors are of great significance for the research on water damage of asphalt pavement.In addition,from the perspective of damage mechanics,water damage to asphalt pavement is actually a kind of fatigue damage phenomenon in which asphalt mixture is damaged under the combined effect of pore water pressure and vehicle load.Therefore,the fatigue damage theory is used to explain the phenomenon of pavement water damage,which is unique in understanding the mechanism of water damage and estimating the life of pavement water damage.At present,the related research is almost blank,and it needs to be developed urgently.In view of the above,this paper uses the theory of fluid-solid coupling of porous media and the principle of fatigue damage to study and analyze the super pore water pressure of the saturated asphalt pavement and its induced pavement damage.The specific work and results are as follows:(1)Analysis of pore water pressure and dynamic mechanical response of saturated asphalt pavement under semi-sinusoidal cyclic loading.The results show that the pore water pressure inside the asphalt pavement under positive and negative cycling conditions under cyclic loading.The positive maximum value(expressed as hydraulic diffusion)is located in the middle and lower parts of the surface layer.The size is 300kPa～500kPa,which is about the tensile strength of the asphalt mixture.The repeated action of pore water pressure of this order of magnitude will inevitably lead to a decrease in the strength of the mixture and a tendency to loosen it;(2)The main factors affecting the pore water pressure of the pavement were studied.The results show that the permeability coefficient and tire pressure of different layers of the pavement are the main factors affecting the size and distribution of pore water pressure.When the permeability coefficient of the upper layer increases,the pore water pressure decreases and the permeability of the base layer can also decrease Peak pore pressure,but water penetration at the base layer may increase the subgrade humidity;(3)Exploring the damage evolution model of asphalt mixture dominated by pore water pressure,and based on this,the fatigue damage mechanics numerical analysis of the water damage phenomenon of asphalt pavement is performed.The results show that the damage evolution model considering the leading role of pore water pressure is reasonable,and the numerical analysis of pavement water damage fatigue damage also provides a valuable reference for water damage damage analysis.