The dynamic mechanical properties of dam concrete play a critical role in the seismic design of dams. Conducting experiments on large-scale fully graded specimens to accurately obtain the mechanical properties of dam concrete is a challenging task. Dam concrete performance is typically evaluated using standard-sized wet-screened specimens. Therefore, it is essential to understand the relationship between the mechanical properties of fully graded and wet-screened specimens under dynamic loading; however, research in this field is scarce. This study investigated the dynamic flexural and compression tests of fully graded and wet-screened dam concrete specimens under strain rates corresponding to seismic loading. The strain rates for the flexural tests were set to 10⁻⁶ s⁻¹, 2 × 10⁻⁴ s⁻¹, 8 × 10⁻⁴ s⁻¹, and 3 × 10⁻³ s⁻¹, while the strain rates for the compression tests were set to 10⁻⁶ s⁻¹, 5 × 10⁻⁴ s⁻¹, 8 × 10⁻³ s⁻¹, and 2 × 10⁻² s⁻¹. Failure modes and strain–stress curves were obtained for various strain rates. Based on the experimental data, the strength, elastic modulus, crack propagation velocity, cracking stress, cracking strain, peak compressive strain, and compressive energy absorption capacity of dam concrete under dynamic strain rates corresponding to seismic loading were determined. The effects of strain rate on these mechanical properties of dam concrete were analyzed. The relationship between fully graded and wet-screened concrete was explored, leading to a linear empirical formula for predicting the strength and elastic modulus of dam concrete based on wet-screened concrete test data. This study enriches the experimental research on the mechanical properties of dam concrete, deepens the understanding of the relationship between fully graded and wet-screened specimens, and provides scientific experimental data to support the seismic safety design of dams.

The dynamic fracture behavior of mass concrete is crucial to the dynamic analysis and safety evaluation of concrete dams subjected to strong earthquake shocks in the framework of fracture mechanics. In the presented research, cylindrical specimens with a ring of preset cracks were cast by three-graded mass concrete, and direct tension tests were performed with two loading rates considered, i.e., 10⁻⁶/s for quasi-static loading and 10⁻³/s for dynamic loading. The load–crack mouth opening displacement (P-CMOD) curves were obtained, from which the fracture toughness, fracture energy, and characteristic length of the mass concrete were obtained. In this process, the influence of the eccentricity in the tests was compensated by the numerical modeling of the tests. Next, the crack propagation process of the mass concrete was modeled using the extended finite element method. From the test results, it is found that, under quasi-static loading, the crack generally propagates along the interface between the aggregates and the matrix, while, under dynamic loading, more aggregates are fractured. As compared to the case of quasi-static loading, the energy absorption capacity, fracture energy, and fracture toughness increase for dynamic loading, while the characteristic length decreases. Moreover, the numerically predicted P-CMOD curves agree reasonably well with the experimental measurements.

Interfacial crack is much more complicated than a crack in homogeneous material. The crack is always in mixed-mode even for symmetrical geometry and symmetrical load, and the stress intensity factor has a complex value, which poses great challenges to numerical modelling. In some cases, there is surface traction on the crack faces, which can be crucial to the stability of the crack. In the presented research, a procedure is brought forward for analysis of interfacial crack with arbitrary surface traction based on the Scaled boundary finite element method(SBFEM). The surface traction on the crack is firstly divided into two parts, one in the direction normal to the crack face and the other in the tangential direction. Then each part is further divided into a series of power function of the radial coordinate. The solution for each can be solved semi-analytically by the SBFEM and is then superimposed to get the total solution. With this procedure, the stress and displacement are solved analytically in the radial direction, and the stress singularity at crack tip is obtained with high precision without refined mesh. Both anisotropic and isotropic materials can be considered. For validation of the procedure, a plate containing an interfacial crack and assuming different material propertes and different surface traction is investigated. Sensitivity analysis is also performed concerning the plate geometry and material properties. Finally the model is applied to solving the stress intensity factors of an interfacial crack of a gravity dam filled with water.