Cemented sand and gravel (CSG) has a wide range of applications in dam construction, and its properties are between rockfill and roller compacted concrete (RCC). A difference in gel content will result in a variance in CSG’s structure and mechanical properties. To investigate the intricate structural mechanical properties of CSG, this study conducted a series of laboratory tests and associated discrete element analyses. Accordingly, the evolution law of the strength parameters of CSG is explored and a statistical damage constitutive model suitable for CSG is established. The main contributions of this study are as follows: (1) The failure mechanism of the CSG was described from the microscopic level, and the evolution law of the strength parameter cohesion and friction angle of the CSG was analyzed and summarized. (2) Based on the particle flow model, the energy development law and the spatiotemporal distribution law of acoustic emission (AE) provide illustrations of the strain hardening–softening transition features and the interaction between cohesion and friction of CSG. (3) The evolution function between the strength parameter and the strain softening parameter was built, and the critical strain softening parameter was determined by the microcrack evolution law of the particle flow model. (4) The accuracy of the evolution curve was confirmed by comparing it to experimental results. (5) Based on the relationship between cohesion loss and material damage, a statistical damage constitutive model was developed using the improved Mohr–Coulomb strength criterion as the micro strength function. The constitutive model can accurately describe the stress–strain curves of CSG with different gel content. Furthermore, the model reflects the strain hardening–softening properties of CSG and reveals the relationship between the weakening of cohesion and material damage at the microscopic level. These findings provide valuable guidelines for investigating the damage laws and microcosmic failure features of CSG and other relevant materials.

Ship lock project currently demonstrates a distinct cyclical pattern, accumulating latent hazards that pose a significant threat to project safety. Seepage safety (the condition in which the seepage risk is reduced to an acceptable level) serves as a crucial indicator in the safety risk assessment index system for ship lock project construction, thus necessitating an in-depth analysis of the risk factors impacting seepage safety. Utilizing a ship lock project in China as a case study, this study employs the finite element method (FEM) to analyze the seepage field of the ship lock foundation pit basin and proposes a comprehensive set of methods for risk evaluation and warning models pertaining to seepage safety risks in ship lock engineering. This study reveals that the obstruction of dewatering wells and imperfections in the diaphragm wall are the primary factors contributing to seepage damage. The investigation conducted a quantitative analysis of the impact of these two factors on the seepage field of the ship lock pit, considering pore pressure, water head, gradient, and flow velocity. A comprehensive set of evaluation indicators for seepage safety was formulated, drawing on the principles of multi-objective optimization, and a method for delineating the safe range of ship lock pit excavation under seepage action was proposed. Subsequently, an integrated seepage safety risk assessment system for ship lock pit excavation engineering was established. These research findings offer a scientific foundation for the management of seepage safety in ship lock pit excavation engineering and provide valuable references and guidance for the development of anti-seepage systems.

Direct construction of the complete overlying soil deposit is generally impractical in centrifuge tests of deeply buried saturated sand, whereas conventional solid surcharges introduce additional mass and inertial effects that may alter the shaking input and dynamic boundary conditions. To address this limitation, a reaction-constrained airbag method was developed to apply equivalent overburden pressure. A reaction cover plate installed at the top of the model container restrained airbag expansion, thereby converting controllable air pressure into a stable and uniformly distributed load on the sand surface and adjusting the initial effective stress without introducing a massive surcharge. Centrifuge shaking-table tests were conducted using the ZJU-400 centrifuge at 50 g. Airbag pressures of 70 and 200 kPa were applied to reproduce equivalent burial-depth ranges of 10–30 m and 30–50 m, respectively. Sinusoidal motions with identical durations, a prototype peak acceleration of 0.4 g, and frequencies of 2 and 3 Hz were imposed. Acceleration, pore-water-pressure, and interlayer shear responses were analysed together with Arias intensity, Fourier spectra, time–frequency representations, and wavelet-based energy distributions. The results show that the two airbag pressures produced stable and clearly differentiated stress conditions, demonstrating the effectiveness of the proposed method. Under shallower burial conditions, the excess pore-water-pressure ratio and dissipated energy first decreased and then increased towards the surface, accompanied by concentrated shallow-layer shear deformation and a higher liquefaction potential. Under deeper burial conditions, the higher initial effective stress enhanced soil-skeleton confinement and the continuity of dominant-frequency transmission, while markedly suppressing irreversible deformation and pore-pressure buildup. At all measurement locations, the dominant frequency remained controlled by the fundamental frequency of the input motion. The shallower condition further exhibited dominant-frequency transmission in the middle layer and frequency-band redistribution in the shallow layer. The proposed system provides low additional mass, uniform and adjustable loading, and good compatibility with dynamic centrifuge testing, offering a new approach for reproducing the stress state of deeply buried soil layers.

With the rapid development of coastal and nearshore engineering projects in China, geotextile pipe and bag (GPB) structures have been increasingly applied in marine land reclamation and coastal protection works. To better understand the mechanical behavior of GPB structures on soft soil foundations, this study conducts a systematic investigation into the mechanical properties of both soft soils and GPBs using a physical model test system. By integrating numerical simulations, the stress–deformation characteristics of GPB structures on soft soils and the evolution of pore pressure are further analyzed. The results indicate that the compression curve of soft soil exhibits significant nonlinearity, with silt showing higher apparent compressibility than silty clay. Experimental data yielded the compression coefficient λ and rebound coefficient μ for both soil types. As consolidation pressure increases, deviatoric stress in the soft soil rises notably, demonstrating typical strain-hardening behavior. Based on these findings, the critical state effective stress ratio M was determined for both soil types. The study also establishes the development laws of cohesion c and friction angle φ during soil consolidation, as well as the variation of pore water pressure under different confining pressures. Interface tests clarify the relationships between cohesion and friction angle at the interfaces between geotextile pipe bags and sand, and between adjacent pipe bag layers. Numerical simulations reveal that the reclamation construction process significantly influences structural horizontal displacement. Significant stress concentration occurs at the toe of the slope, while the central portion of the pipe-bag structure experiences maximum tensile stress—still within the material’s allowable stress limit. The installation of drainage boards effectively accelerates pore pressure dissipation, achieving nearly complete consolidation within one year after construction. This research provides a scientific foundation and practical engineering guidance for assessing the overall stability and safety of (GPB) structures on soft soil foundations in coastal regions.