Study On Mechanical Properties And Viscoelastic Damage Of Hydraulic Asphalt Concrete At Different Temperatures

Hydraulic asphalt concrete has the characteristics of good impermeability,strong deformation capacity,and excellent work performance,and has been widely used as the antiseepage material for the core wall and face plate of earth-rock dams.However,asphalt concrete is highly sensitive to temperature and strain rate,especially the anti-seepage panels in western my country,which face the test of extreme temperature and seismic action during the service period of the panels.At the same time,asphalt concrete is a heterogeneous viscoelastic material composed of mineral aggregates,asphalt,coarse aggregates,and fine aggregates,and exhibits certain plastic deformation after bearing loads.The theory of continuum mechanics cannot truly reflect its mesoscopic level mechanical response.Therefore,this paper studies the macroscopic mechanical properties of asphalt concrete from three aspects:dynamic compression properties,bending properties and indirect tensile properties.And based on the discrete element method,the viscoelastic damage unit and elastoplastic damage unit are coupled in parallel to study the dynamic compression failure behavior and mechanism of asphalt concrete from the mesoscopic level.The main research contents and results are as follows:（1）Uniaxial compression tests of hydraulic asphalt concrete at different temperatures（10℃、0℃,10℃、20℃）d strain rates(10^-5/s、10^-4/s、10^-3/s,10^-2/s)were carried out.The damage pattern,stress-strain full curve,compressive strength,elastic modulus and energy absorption capacity of asphalt concrete were analyzed.The results show that the failure mode of asphalt concrete gradually changes from brittle failure to ductile failure with the increase of temperature,and the damage degree gradually deepens with the increase of strain rate.The stress-strain curve shows obvious strain hardening phenomenon when the temperature is above 0℃,and the curve softening phenomenon is more obvious when the temperature is-10℃,and the increase of the strain rate increases the stiffness of the curve.The compressive strength,elastic modulus and energy absorption capacity increase with decreasing temperature and increasing strain rate.The temperature influence factor of compressive strength and the change law of temperature conform to the Logistic function model,and the logarithm of compressive strength dynamic enhancement factor and strain rate is linear when the temperature is low,and exponential when the temperature is high.（2）The flexural and indirect tensile properties of asphalt concrete were studied by conducting three-point bending beam tests and split tensile tests under the four temperature conditions of-10℃,0℃,10℃,and 20℃.The results show that:When the temperature is lower than 0℃,the load-mid-span deflection curve and load-deformation curve of asphalt concrete show elastic brittleness,and the load reaches the peak point and then falls like a cliff.As the temperature increases,the strain hardening trend of the curve gradually obvious.The flexural strength,flexural modulus,fracture energy and splitting tensile strength of hydraulic asphalt concrete gradually increase with the decrease of temperature,and the variation law of flexural strength temperature influence factor,flexural modulus,splitting tensile strength and temperature It conforms to the Logistic function model and fits well with the established function.（3）Based on the discrete element principle,the viscoelastic-elastoplastic damage constitutive model and its force-displacement law are constructed.Compile the dynamic link library file through C++language.Secondary development of PFC software interparticle contact constitutive model.3D Numerical Model of Asphalt Concrete Established Using Fish Language Parameterization.The uniaxial dynamic compression test of asphalt concrete was simulated and the mesoscopic parameters were calibrated.The calculation results show that the mechanical performance index obtained by the numerical simulation is basically consistent with the laboratory test data,which verifies the accuracy of the model.The point contact force of the two stages,the number of microcracks and the number of fragments after final cracking gradually increase with the decrease of temperature and the increase of strain rate,and the maximum point contact force of the numerical specimen in the fifth stage is related to the residual stress of the model.The microcracks at the two stages are mainly shear cracks,and the number of microcracks gradually increases with the increase of strain.The fragment distribution of the numerical specimen is basically consistent with the failure pattern obtained from the indoor uniaxial dynamic compression test.The research results of this paper can provide a certain engineering reference value for the daily operation of asphalt concrete anti-seepage panels,earthquake prevention and disaster reduction.