Experimental And Theoretic Study On The Dynamic Behavior Of Saturated Large Aggregate Concrete Under Biaxial Loading

Most hydraulic mass concrete structures(i.e. piers, dams and offshore platform), are always subjected to saturation state. But the study on dynamic multiaxial mechanical property of large aggregate concrete is very little. Therefore, it is necessary to research the failure mechanism of saturated large aggregate concrete through experiment and theory analysis. The servo-hydraulic multiaxial testing machine designed by Dalian University of Technology is used to investigate the large aggregate concrete dynamic compressive strength under different water contend(i.e. drying, natural and fully saturated), strain rates(10-5/s,10-4/s,10-3s,10-2/s) and stress ratios(1:0,1:0.25,1:0.5,1:0.75,1:1).(1) The test investigates the dynamic mechanical property of large aggregate concrete, such as failure pattern, ultimate strength, deformation characteristic, stress-strain curve and ultimate strain. The research shows that concrete dynamic compressive strength reaches the maximal value at the stress ratio of 1:0.5, and the saturated concrete dynamic compressive strength is larger than the dried concrete at high strain rate. Concrete strain increases with the decrease of the strain rate, and the saturated concrete strain is observably larger than the dried concrete. Base on the experiment and theory, considering water contend, strain rate and stress ratio, a failure criterion is proposed. Comparing with other failure criterions, the one in this paper is more suitable.(2) Linear elastic fracture mechanics is used to discuss the failure mechanism of saturated concrete. This research shows that concrete compressive strength will decrease with the increasing of the crack size. An approximate method for calculating the dynamic fracture toughness of concrete under different water content is proposed. The calculated results with this method agree well with available experimental data, indicating that the proposed method can, to some extent, predict the dynamic fracture property of concrete.