Impact compression test and dynamic triaxial unified strength criterion for concrete under freeze-thaw cycle action

Directing at the concrete material, a set of freeze-thaw (FT) cycle tests with a temperature range of - 20 °C to 20 °C and FT cycles from 0 to 50 times were carried out in this paper, series of uniaxial and triaxial impact compression tests with high strain rate (about 10¹ s^-1-10³ s^-1) were completed on the Split Hopkinson Pressure Bar (SHPB) system, and the dynamic compression strength, failure mode and the influencing rules were analyzed. According to the test results, the rate-dependent expression of concrete strength parameter cohesion was derived based on the unified strength theory and the rate-dependent physical mechanism of concrete strength thermal activation and cohesive coexisting and competing. Through developing the classical static unified strength criterion into a dynamic unified strength criterion, the dynamic triaxial unified strength criterion of concrete under different FT cycles was established, and its correctness and applicability were proved from both the necessity analysis and the experimental verification. On this basis, the influence characteristics of intermediate principal stress effect and strength criterion on the calculation of concrete dynamic compression strength were discussed.