In order to explore the influence of different layer treatment methods on the macro- and meso-mechanical properties of cemented sand and gravel (CSG), in this paper, the shear behavior of CSG material was simulated by a three-dimensional particle flow program (PFC3D) based on the results of direct shear test in the laboratory. In shear tests, untreated CSG samples with interface coating mortar and chiseling were used, and granular discrete element software (PDC3D 7.0) was used to establish mesoscopic numerical models of CSG samples with the above three interface treatment methods, in order to reveal the effects of interface treatment methods on the interface strength and damage mechanism of CSG samples. The results show that, with the increase in normal stress, the amount of aggregate falling off the shear failure surface increases, the bump and undulation are more obvious, and the failure mode of the test block is inferred to be extrusion friction failure. The shear strength of the mortar interface is 40% higher than that of the untreated interface, and the failure surface is smooth and flat under different normal stresses. The shear strength of the chiseled interface is 10% higher than that of the untreated interface, and the failure surface fluctuates significantly under different normal stresses. Through the analysis of the fracture evolution process in the numerical simulation, it is found that the fracture of the sample at the mortar interface mainly expands along the mortar–aggregate interface and the damage mode is shear slip. However, the cracks of the samples at the gouged interface are concentrated on the upper and lower sides of the interface, and the damage mode is tension–shear. The failure mode of the samples without surface treatment is mainly tensile and shear failure, and the failure mode gradually changes to extrusion friction failure.

This study proposes a high-strength bottom-bar interlocking and anchorage precast beam–column joint (HSRU-PBCJ), which utilizes high-strength longitudinal reinforcement combined with U-shaped anchorage at the beam bottom. Low-cycle reversed loading tests were conducted on two precast specimens and one cast-in-place specimen to evaluate their seismic performance. Based on these results, parametric analyses were conducted through numerical simulations to investigate the effects of axial compression ratio, concrete strength, beam-end longitudinal reinforcement strength, and beam-end longitudinal reinforcement ratio on the seismic performance. The results indicate that the proposed joint exhibits stable and full hysteresis loops, cumulative energy dissipation comparable to that of the cast-in-place joint, and a 23.94–26.39% increase in equivalent viscous damping after yielding, achieving a displacement ductility coefficient of 4.14, which confirms its substantially improved seismic performance. The parametric study shows that maintaining a moderate axial compression ratio (≤0.6) enhances both load-bearing capacity and energy dissipation, whereas excessive values result in strength reduction. Increasing the beam-end longitudinal reinforcement strength significantly improves load-bearing capacity but may reduce energy dissipation. In addition, improving concrete strength and appropriately increasing the reinforcement ratio can further enhance both load-bearing capacity and energy dissipation, although a balance between seismic performance and economic considerations is recommended.

By utilizing the Kosambi–Cartan–Chern (KCC) geometric theory, this paper is dedicated to providing novel insights into the Liu dynamical system, which stands out as one of the most distinctive and noteworthy nonlinear dynamical systems. Firstly, five important geometrical invariants of the system are obtained by associating the nonlinear connection with the Berwald connection. Secondly, in terms of the eigenvalues of the deviation curvature tensor, the Jacobi stability of the Liu dynamical system at fixed points is investigated, which indicates that three fixed points are Jacobi unstable. The Jacobi stability of the system is analyzed and compared with that of Lyapunov stability. Lastly, the dynamical behavior of components of the deviation vector is studied, which serves to geometrically delineate the chaotic behavior of the system near the origin. The onset of chaos for the Liu dynamical system is obtained. This work provides an analysis of the Jacobi stability of the Liu dynamical system, serving as a useful reference for future chaotic system research.

In order to study the influence of construction interfaces on the safety of middle-low and 100-m cemented sand gravel (CSG) dams, direct shear tests of the construction interfaces with laying mortar and roughening under four different normal pressures are firstly conducted; shear stress–shear displacement curves and interface parameters for the interface models are obtained. Then, finite element models are established using a modified Duncan–Chang constitutive model and a zero-thickness interface model. Displacements, stresses, and anti-sliding stability coefficients of the construction interfaces are obtained, load-bearing capacity is analyzed using the water bulk density overload method, and the obtained results are compared with those of the model without consideration of the construction interfaces. The results show that the obtained displacements and stresses become larger or remain constant when the construction interfaces are considered. The two interface treatment methods (laying mortar and roughening) meet the requirements of anti-sliding stability, and the load-bearing capacity of the construction interface with laying mortar is greater. This study reveals the influence of construction interfaces on the overall mechanical behaviors of the CSG dams and provides technical guidelines for the two construction interface treatments.