This research aims to investigate the potential of engineering waste marine silt stabilized by a self-developed stabilizing chemical additive called PZ-1 as a subgrade filler. PZ-1 is composed of calcium carbide residue (CCR) and plant ash (PA) under an optimal composition ratio determined by coupling particle swarm optimization with a support vector machine (PSO-SVM). The effect of curing agent dosage (w_g), temperature (w_T), number of dry-wet cycles (N_dw), and organic matter content (w_o) on the micro-macro behavior of the stabilized silt were investigated via the unconfined compressive strength (UCS) test, the scanning electron microscope (SEM) test, and the X-ray diffraction (XRD) test. The experimental results demonstrate a significant positive effect of PZ-1 on the unconfined compressive strength (q_u) of marine engineering waste silt with curing agent contents of 0~8%. It was also found that strength improvement of the stabilized silt can be attributed to the formation of gelling substances such as C-S-H and calcite. The water resistance of the stabilized silt can be enhanced by increasing the dosage of the curing agent. Moreover, the organic matter content and ambient temperature have significant effects on the dry-wet cycle tolerance of solidified soil, among which temperature exhibits a more obvious impact.

This paper presents a simple but workable constitutive model for the stress–strain relationship of sandy soil during the process of tunneling construction disturbance in coastal cities. The model was developed by linking the parameter K and internal angle φ of the Duncan–Chang model with the disturbed degree of sand, in which the effects of the initial void ratio on the strength deformation property of sands are considered using a unified disturbance function based on disturbed state concept theory. Three cases were analyzed to investigate the validity of the proposed constitutive model considering disturbance. After validation, the proposed constitutive model was further incorporated into a 3D finite element framework to predict the soil deformation caused by shield construction. It was found that the simulated results agreed well with the analytical solution, indicating that the developed numerical model with proposed constitutive relationship is capable of characterizing the mechanical properties of sand under tunneling construction disturbance.

Calcareous sand, ubiquitous in the geotechnical makeup of the South China Sea, exhibits both compressibility and vulnerability to fragmentation when subjected to external loading, spanning a spectrum from typical to extreme conditions. This investigation aims to quantitatively assess the compression and particle breakage characteristics of calcareous sand under varied parameters, including relative density, saturation, applied loads, and loading paths, specifically focusing on sustainable geotechnical methodologies. Through a series of confined compression tests, this evaluation employed the relative breakage ratio and fractal dimension as key evaluative metrics. The results indicated that employing this integrated approach offered a more comprehensive understanding of calcareous sand breakdown mechanisms than relying on a singular particle breakage index. Furthermore, an increase in relative density can induce a transition in particle contact behavior, shifting from point-to-point interactions to face-to-face contact, thereby reducing inter-particle stress and minimizing grain breakage, particularly under loads below 200 kPa. Increasing loads exacerbated particle breakage, with finer particles predominantly initiating this process. During reloading, pore ratios across various load levels surpass those observed during initial loading, except at 1600 kPa, where a decline in pore ratio was noted, coinciding with pore water extrusion and the onset of new particle fracturing. The lubricating effect of water reduces inter-particle friction, enhancing stress concentration at particle edges and localized particle breakage, thereby increasing the presence of finer particles without significantly altering the overall structure. Notably, the influence of pore water pressure is evident during the reloading phase. These findings contribute to a refined theoretical framework for predicting coastal erosion risks and devising effective environmental protection strategies for sustainable coastal engineering practices.

An analytical three-dimensional slope reliability evaluation framework was developed in this work independent of use of numerical simulations. The slope stability analysis was necessarily carried out by utilizing an extended three-dimensional Morgenstern–Price method, which was characterized by analytical formulations and competitive computational efficiency. Incorporation of the presented stability analysis method into response surface methodology led to an effective slope reliability evaluation framework. The applicability and superiority of this framework was examined and validated using a real complicated landslide case reported in practice, and a hypothetical slope example widely adopted in the literature. The impact of correlation coefficients and probability distribution patterns on the slope reliability assessment results was further addressed to derive additional benefits of this framework.