Study On Influence Of Temperature And Loading Rate On Properties Of Hydraulic Asphalt Concrete

Embankment with asphalt concrete core has been widely concerned because of its good performance such as impermeability,deformation adaptability and self-healing ability for cracks.In resent years,more and more scholars and experts have recognized it is suit to construct asphalt concrete core as impervious structure for embankment in the areas without advantages such as complex geological or high earthquake incidence areas.So far in china,the highest dam with asphalt concrete core rock-fill dam,height of 174m for dam and 132m for asphalt concrete core wall.It is still have not enough courage to build asphalt concrete core dams with height of 200m,300m or even higher.There are some concerns about building an embankment with asphalt concrete wall of 200m,300m or higher.As we know,asphalt concrete is a kind of viscoelastic plastic material,it is significantly affected by temperature and loading rate.The temperature of asphalt concrete core is always changing during construction and varies in different areas.However,there is no systematic research on the effect of temperature and loading rate on the performance of hydraulic asphalt concrete.This paper conducts experimental to research on the shear resistance of hydraulic asphalt concrete,the performance of tension and conpression,triaxial compression performance,study on long-term creep property and hydraulic tracturing resistance.The main results are as follows:(1)By slant sheat test at different temperature and loading rate,we can conclude the stress-strain behavior of hydraulic asphalt concrete.When the shear stress is less than 50%of the shear strength,the shear stress has a liner relationship with the shear strain,and the temperature and strain rate have significant effects on the strength and modulus.The time-temperature superposition is used to fit the main curve of mechanical parameters of hydraulic asphalt concrete under slant shear stress,and the relationship between shear modulus,shear strength,shear strain rate and temperatue is established.(2)Through the test of repeated slant shear tests under different temperature and different shear strain rates,studis the law of shear modulus of hydraulic asphalt concrete under the control of maximum shear strength.Then,studes the stress relaxation of hydraulic asphalt concrete after the slant shear test.The 25%?max test results show that the shear modulus are not change much with the increase of shear times;the 50%?max test results show that the shear modulus are different degrees of attenuation with the increase of shear times;and lower temperature or higher shear rate,the greater of attenuation degree of shear modulus;the 75%?max test results show that the shear modulus are attenuation obviously with the increase of shear times.(3)Tri-axial compression test were carried out at different temperature and strain rate,the results show that the stress-strain-strength of hydraulic concrete is very sensitive to temperature and loading rate.Taking the test condition of axial strain 0.1%/min as an example,the strength at 5? is 3.5MPa,while it is only 0.1MPa at 60?;similarly,taking 35? as an example,the axial strain rate at 1%/min has a strength of 1.8MPa,while it is 1.8MPa at 0.001%/min.It also shows that hydraulic asphalt concrete has little or no shear resistance at high temperature or very low strain rate.(4)From the creep test,we can conclude the influence of temperature on creep stability modulus.The stability modulus is lower than 10MPa when the temperature is high than 20?.But the temperature is lower than 20?,the stability modulus increases obviously,and it will increase to 60MPa at 5?.(5)Base on the tensile test of hydraulic asphalt concrete at different temperatures and strain rates,study on the effect of temperature and loading rate on tensile stress-strain.When the temperature is lower than 10?,brittle failure occres.Using the time-temperature superposition to reach the relationship between tensile strength,tensile modulus and loading rate.Combined with the results of dynamic compressive characteristics,Mohr-Coulomb criterion was adopted to determine the cohesion C and friction Angle of hydraulic asphalt concrete in tension and compression models.(6)The influences of striking frequency on the porosity of hydraulic asphalt concrete are resieved as follow:with the increase of frequency,the porosity of asphalt concrete decreases gradually,and until to a stable value.When it's exceed to 35 times,will meet the requirement of porosity less than 2%.When less than 40 times,there is a linear relationship between the frequency and Log porosity.(7)Through the hydraulic fractureing test of asphalt concrete under different temperature,different loading mode and different defect conditions,study on the influence of hydraulic fracturing performance of asphalt concrete.As the porosity of specimens increases,the water pressure of failure decreases,and the axial deformation also decreases.The lower the temperature,the greater the water pressure and the smaller the deformation.With the increase of the prefabricated joints,the water pressure of failure of the specimen decreases,and the deformation tends to decrease,but the overall deformation does not change much.