Permeable concrete piles, which combine the advantages of rigid piles and drainage consolidation techniques, have been widely applied in soil foundation treatment. In this study, the optimal mix proportion of the permeable concrete pile material was first determined through laboratory experiments; subsequently, based on the experimental results, numerical simulations were employed to investigate the load-bearing characteristics of composite foundations reinforced with permeable concrete piles under applied loads. The experimental results indicate that when the designed porosity is set between 20% and 35%, and the water-to-cement ratio is 0.3, the actual porosity closely approximates the design value, achieving a favorable balance between compressive strength and permeability. Numerical simulation results reveal that as the axial force in the permeable concrete piles attenuates with depth, the side friction of piles exhibits an overall increasing trend. Compared with impermeable piles, the pile–soil stress ratio and the load-sharing ratio of permeable piles gradually decrease under high loads; furthermore, the settlement and pile–soil stress ratio of the composite foundation is significantly influenced by factors such as pile length, pile diameter, cushion modulus, inter-pile soil modulus, and the modulus of the pile material.

The soil parameters of artificial soil foundations exhibit significant spatial variability due to particle sorting during the filling process, which follows a trend that is distinct from that of natural soft foundations. Based on this observation, a non-stationary random field model is proposed, in which the undrained shear strength decreases along the horizontal filling direction and increases along the vertical deposition direction. The impact of the non-stationary random field model on the vertical bearing capacity of pile foundations is analyzed and discussed with Monte Carlo simulations. The results indicate that the mean and coefficient of variation of the undrained shear strength significantly affect the vertical ultimate bearing capacity of pile foundations, whereas the effects of the random field correlation distance and vertical non-stationary trend coefficient are relatively minor. Under the influence of the horizontal non-stationary trend coefficient, the mean vertical ultimate bearing capacity of pile foundations decreases with the horizontal distance between the pile and the backfill entrance. Moreover, the rate of decrease diminishes linearly with the horizontal non-stationary trend coefficient. A predictive formula for the vertical ultimate bearing capacity of pile foundations is proposed, and its applicability is verified.

The accumulation of silty soils and industrial solid waste not only results in a significant waste of land resources but also causes environmental pollution. Phosphogypsum and cement are commonly utilized as binding agents for the solidification of silt in engineering applications. However, the use of PG and cement alone may lead to issues such as insufficient strength, crack formation, and poor durability. Therefore, this research considered and employed a two-phase stabilization method using phosphogypsum and cement to solidify silt. Additionally, to further enhance the durability of the stabilized silt, polypropylene fiber (PP) and sodium sulfate (Na₂SO₄, NS) were incorporated. The effects of two-phase phosphogypsum and the proportion of hemihydrate phosphogypsum (BHPG) in the two-phase phosphogypsum on the strength characteristics of the stabilized silt were investigated through unconfined compressive strength tests and durability tests. The results show that when the content of two-phase phosphogypsum is 5%, and the proportion of BHPG in the two-phase phosphogypsum is 20%, the 28-day unconfined compressive strength of the stabilized silt reaches 1.42 MPa, and the deformation modulus is 95.5 MPa. After incorporating sodium sulfate (NS), the water and frost resistance of the stabilized silt significantly improved. The microstructural analysis shows that NS promotes the formation of ettringite. Furthermore, an excessively high proportion of hemihydrate phosphogypsum (BHPG) in the two-phase phosphogypsum content can lead to dihydrate phosphogypsum (2HPG) not being encapsulated by hydration products, which results in a less dense structure of the solidified silt and a decline in performance.

For the purpose of ensuring the construction safety of tunnel excavation, it is necessary to adopt a suitable pre-support technology to reinforce the surrounding rock. The pipe roof reinforcement method and the leading ductule method are the most commonly used and classical technologies during tunnel construction. This paper adopts the Huashan tunnel and the Xianglianshan tunnel as the engineering background, the numerical simulation is established based on Midas/GTS to analyze the mechanical performance of the pre-supports formed by the two methods during excavation, then the obtained results, such as stress, deformation, plastic zone, and settlement, are analyzed and discussed. The analysis and discussion illustrate that, during excavation, compared to the leading ductule reinforcement method, the pipe roof reinforcement method can effectively control the vault settlement and improve the stress state of the lining structure, as well as prevent the stress release from the surrounding rock. Thus, the pipe roof reinforcement method shows better reinforcement effectiveness and ensures construction safety.

To address the stability of high embankment slopes and investigate the influence of spatial variability of gravel soil on slope stability, this study proposes a simplified reliability analysis method of slope stability. Based on FLAC^3D, a numerical model was developed to simulate slope behavior, and a linear regression-based empirical model was formulated to quantify the relationship between soil pressure and spatial variability indicators (e.g., coefficient of variation and correlation length). By mapping the spatial variability of soil parameters to soil pressure fluctuations, the slope reliability was evaluated through the first-order second-moment method (FOSM). The results demonstrate that the mean value of internal friction angle has a significant effect on the stability of gravel soil embankment slope, whereas the coefficient of variation in this parameter is limited. Furthermore, the correlation length of soil spatial variability shows marginal influence on stability outcomes. The computational model was validated against case study data, demonstrating its applicability for practical slope stability assessments.