The shear (τ_p), creep (τ_c), and long-term shear (τ_∞) strengths of moraine soil are mechanical properties of high concern during the engineering construction and management process and were obtained by conducting large-scale direct shear and shear creep tests on the soil layer at the Dadu river bridge in Luding, China. The size of the test samples was about 1.0 × 1.0 × 0.50 m (length × width × height). The shear strength and creep behavior under different normal (σ) and shear (τ) stresses were analyzed, and the long-term shear strength was obtained from stress-displacement isochronal curves during the creep process. The results indicate that the shear strength of moraine soil relates to the content and distribution of large particles. The shear strength parameter of moraine soil is 0.765 (φ = 37°) and the cohesion parameter (c) is 64.2 kPa. The moment of the maximum creep displacement rate at the primary creep stage depends on the shear stress. The step-like increasing and jumping of shear creep displacement are evident during the middle-process of the secondary creep stage (e.g., 20–60 h when τ is 411 kPa under σ of 300 kPa), due to large particles rotating or overturning under high shear stresses. The empirical Burgers model predicts the creep displacement well. The ratio (τ_∞/τ_p) of long-term to shear strength ranges from 0.53 to 0.92, indicating that the creep effect has decays in the shear strength of moraine soil. The ratio (τ_∞/τ_c) of long-term to creep strength ranges from 0.65 to 0.85, indicating that moraine soil could easily transfer from viscous creep deformation to shear failure when the loading stress is higher than long-term strength. The results provide a valuable reference for shear strength analysis and long-term strength assessment of moraine soil regions.

Understanding the long-term creep behaviors of asphalt concrete core materials is crucial to the safety of embankment dams. This study systematically analyzes the creep behavior of asphalt concrete materials under a stepped loading path. Static triaxial tests are conducted to determine the stress–strain relation of asphalt concrete core materials. Both stepped loading and separate loading paths are applied on the asphalt concrete samples to analyze the difference between them in terms of the axial strain. To simulate the realistic temperature condition during the operation of dams, the temperature is set to 22.1°C. The test samples are subjected to four confining stresses (i.e., 0.1, 0.4, 0.7, and 1.0 MPa), and the stress levels are 0.2, 0.4, 0.5, and 0.8. For processing the test data obtained under the stepped loading path, the Boltzmann superposition method and Chen’s method are applied. Then, the Burgers model is applied to estimate the stress and strain behaviors of the asphalt concrete materials. The results indicate that asphalt concrete materials characterize in primary and secondary creep stages. The data processed by Chen’s method is much closer to the data of separate loading path than those processed by the Boltzmann method. The Burgers model describes well the creep behavior of the asphalt concrete materials. Thus, it can be applied in the estimation and analysis of the creep behaviors for embankment dams under long-term operation.