Dynamic Compressive Behavior And Discrete Element Simulation Of Asphalt Concrete Under Different Temperatures

Asphalt concrete is a multiphase composite material mixed by asphalt,coarse aggregate,fine aggregate,filler and other materials in a certain proportion.It has excellent anti-seepage characteristics,deformation adaptability and environmental friendliness,so it is widely used in anti-seepage structure of earth-rock dam engineering.Asphalt concrete has a strong temperature sensitivity,the temperature has a significant effect on mechanical properties of the impervious facing which located in high altitude areas especially.In addition,China is a country prone to earthquakes and most of the earth-rock dam anti-seepage structure engineering that have been built in strong earthquake areas,so earthquake action is an influencing factor that must be considered during dam design and operation.Therefore,this paper combinate macro-testing and meso discrete element simulation method to study the dynamic anti-compression mechanical properties of asphalt concrete in different temperature conditions,and studies the failure mechanism of asphalt concrete in different temperature conditions at the microscopic level.On this basis,the relationship between macro and meso mechanical response was established.The main research content has the following aspects:(1)The experimental study on the dynamic compressive properties of asphalt concrete was carried out at the temperature conditions of-10? to 10?.And the test results showed that the stress-strain curves of asphalt concrete under four strain rates all exhibit strain softening characteristics;and compared with the effect of quasi-static loading(10-5 s-1),the curve is more softened under dynamic load(10-4 to 10-2 s-1),and the greater the strain rate or the lower the temperature,the more obvious the strain softening characteristic.The elastic modulus and peak stress of asphalt concrete increase with decreasing temperature or increasing strain rate,showing obvious low temperature strengthening effect and strain rate strengthening effect.With the joint effect of strain rate and temperature,asphalt concrete appears four failure modes.And four failure modes are microcrack failure,tensile shear failure,splitting failure and fragmentation failure respectively.As the temperature decreases and the loading rate increases,the above four failure characteristics of asphalt concrete appear in turn(2)Based on the test results,the low-temperature stiffening and strain rate enhancement effect of asphalt concrete were studied using temperature enhancement coefficient and dynamic enhancement coefficient.And the mathematical relationship between the peak stress,elastic modulus of asphalt concrete and temperature,strain rate was established(3)Based on the form of the Logistics function and the Weibull damage variables distributed,a mathematical model of the stress-strain full curve of asphalt concrete is established and compared with the test results.The results show that the stress-strain full curve model proposed in this paper reflects characteristic of stress-strain curve of asphalt concrete under different temperature and strain rate(4)Based on the mix proportion of asphalt concrete,a three-dimensional microscopic discrete element model was established to study the microscopic mechanical properties of asphalt concrete under different temperature conditions and load rates,and the internal cracks and energy evolution law of asphalt concrete during the whole process of failure under different temperature conditions were analyzed...