Study On Dynamic Mechanical Properties And Failure Criteria Of Hydraulic Asphalt Concrete Under Compression Shear Action

Hydraulic asphalt concrete is a composite material composed of asphalt cementing aggregates,fillers,etc.,which has the advantages of excellent impervious performance and strong deformation ability,so it has been widely used in the impermeable core wall of earth-rock dams.With the deepening of the western development strategy,the number of asphalt concrete core wall dams in the western region of China has continued to grow,of which a considerable number of dams are located in strong earthquake areas with frequent seismic activity,and asphalt concrete is often in a dynamic compression shear composite stress state during earthquakes,asphalt concrete in different regions has different shear deformation rates during earthquakes,and the stress conditions at different positions of the core wall are also different.Therefore,it is of great significance to study the dynamic mechanical properties of hydraulic asphalt concrete under compression shear action,then establish the corresponding failure criteria to ensure the safety of the impermeable core wall of earth-rock dams.In this paper,the dynamic mechanical properties of hydraulic asphalt concrete at a temperature of 5℃ and 15℃ under the normal stress of 1MPa,2MPa,3MPa and shear rate of 0.0005s^-1,0.001s^-1,0.005s^-1 and 0.01s^-1 were experimentally studied,and on this basis,the failure criteria of hydraulic asphalt concrete under compression shear action were established in combination with the Mohr strength criterion,and the main research contents and conclusions are as follows:（1）Compared with the traditional shear instrument,the compression shear test devices of the two straight shear were independently developed,which can keep the effective shear area unchanged during shearing,the stress distribution on the shear surface is uniform,and the normal force and shear force can be considered independently.（2）The failure mode of hydraulic asphalt concrete under compression shear action was obtained.The results indicate that different normal stresses and shear rates have varying degrees of influence on the failure mode of hydraulic asphalt concrete.The failure mode of the specimen with the increase of shear rate and normal stress changes from adhesive failure to brittle failure stage by stage at a temperature of 5℃.The specimen shows ductile failure at a temperature of 15℃,furthermore,the less number of cracks and the larger the cracking ratio of the aggregate when the greater the shear rate.Under the action of normal stress,the specimen expands along the length direction to both sides,and the expansion phenomenon becomes more obvious with the increase of normal stress.（3）Revealed the changes in the shear stress-strain curve and related parameters of hydraulic asphalt concrete under the action of normal stress and shear rate.According to the results can find that the variation law of the specimen is basically the same before the shear stress-strain curve reaches the peak stress,and after reaching the peak stress shows obvious discrepancies.The shear strength and shear modulus increase while the normal stress and shear rate increase.The peak strain increases as the normal stress decreases or the shear rate increases.The energy absorption capacity first increased and then decreased with the increase of normal stress at a temperature of 5℃.When the normal stress is small,it decreases with the increase of normal stress.When the normal stress is large,it has little effect on the energy absorption capacity at a temperature of 15℃.As the shear rate increases,the energy absorption capacity also increases.In addition,based on the principle of time-stress superposition,the mathematical model of shear strength and shear modulus of hydraulic asphalt concrete considering the interaction between normal stress and shear rate is derived by equivalent conversion of normal stress and time scale,which is in good agreement with the actual value of compression shear test.（4）At different shear rates,analyzed the changes of cohesion c and internal friction angleφ.It was found that the cohesion c increase while the shear rate increase.The internal friction angle φ first increased and then decreased with the increase of shear rate at a temperature of 5℃ and it shows the opposite rule at a temperature of 15℃.（5）Taking the Mohr strength criterion as the theoretical basis,studied the ultimate stress state of hydraulic asphalt concrete under compression shear action,then compared and analyzed the ultimate shear stress range of hydraulic asphalt concrete in the Mohr-Coulomb criterion,parabolic Mohr criterion and hyperbolic Mohr criterion with the compression shear test results,At last,established the compression shear failure criterion of hydraulic asphalt concrete under the Mohr-Coulomb criterion.