Using coal gangue as subgrade filler can not only solve the environmental problems of coal mine waste accumulation but also decrease the subgrade cost, which has important theoretical and practical significance. A series of cyclic triaxial tests was carried out using the large-scale dynamic and static triaxial apparatus (LSDSTA) to investigate the permanent deformation ($\epsilon$) of coal gangue subgrade filler (CGSF) under cyclic loading. Experimental grading was designed by using the fractal model grading equation (FMGE), and then well-grading limits of CGSF were captured. The relationship curve between $\epsilon$ and the numbers of cyclic loading (N) can be divided into three stages, i.e., the rapid growth phase, the deceleration growth phase, and the approaching stability phase. N = 1000 can be used as the criterion for reaching the stable stage of CGSF. The effect of confining pressure (${\sigma }_3^{\prime }$) on $\epsilon$ is related to the level of ${\sigma }_3^{\prime }$. The effect of ${\sigma }_3^{\prime }$ on $\epsilon$ is significant when ${\sigma }_3^{\prime }$ is smaller, whereas the influence of ${\sigma }_3^{\prime }$ on $\epsilon$ is smaller when ${\sigma }_3^{\prime }$ is larger. Furthermore, the influence of grading ($D_f$) on $\epsilon$ of coal gangue samples is significant. With the increase of $D_f$, $\epsilon$ first increases and then decreases, reflecting that there is an obvious optimal grading for coal gangue samples under cyclic loading. Moreover, the effect of compaction degree ($D_c$) on $\epsilon$ of CGSF depends on the level of $D_c$. $\epsilon$ is hardly affected when $D_c$ is smaller, whereas increasing $D_c$ has a significant effect on restraining $\epsilon$ when $D_c$ is bigger. In addition, according to the analysis of the permanent deformation curve for CGSF, the unified calculation model of permanent deformation for CGSF under cyclic loading is established. Compared with the existing permanent deformation models, the proposed model in this paper can better describe the permanent deformation of CGSF under cyclic loading. Finally, the model parameters are analyzed, and the model is verified.

Soil–rock mixture (S–RM) is a heterogeneous granular material commonly used in engineering applications, but achieving uniform particle mixing is challenging. This study investigated the effect of mixing homogeneity on the compaction of S–RM using the discrete element method (DEM). Specimens with varying degrees of mixing were modeled under realistic vibration loading. The results showed that a higher degree of mixing resulted in a smaller void ratio after compaction. The analysis of particle motion and energy dissipation revealed that not all particle motion during vibration compaction was aligned with the direction of the particle system. However, rotation was more prevalent and contributed to densification. Dashpot energy dissipation did not solely promote changes in the void ratio, while slip energy dissipation did lead to changes in the void ratio, but not entirely towards compaction. Rolling slip energy dissipation primarily occurred during the stage of void ratio changes and significantly promoted compaction. The change in strain energy aligned with the trend of the void ratio but did not directly contribute to its promotion.

Controlling the ground settlement and building deformation triggered by shield tunnelling, particularly within water-rich strata, poses a significant engineering challenge. This study conducts a finite element (FE) analysis focusing on the ground settlement and deformation of adjacent structures (with a minimum distance of 2.6 m to the tunnel) due to earth pressure balance (EPB) shield tunnelling. The analysis incorporates the influence of groundwater through a 3D fluid–solid coupling model. This study assesses the effects of tunnelling on the behaviour of nearby buildings and introduces two mitigation strategies: the vertical partition method and the portal partition method. Their effectiveness is compared and evaluated. Our findings reveal that the deformation curves of the stratum and the building are influenced by the accumulation and dissipation of pore pressure. The vertical partition method reduced surface settlement by approximately 70%, while the portal partition method further minimized building deformation but required careful application to avoid issues like uplift. Both methods effectively mitigate the impacts of tunnel construction, with the portal partition method offering superior performance in terms of material use and cost efficiency. This research provides a scientific foundation and technical guidance for similar engineering endeavours, which is vital for ensuring the safety of metro tunnel construction and the stability of adjacent buildings.

The use of geosynthetics in reinforced soil structures (RSSs) requires the experimental and numerical modelling of the soil–geosynthetic interaction to support the design and analysis and deepen the knowledge of RSS systems. Direct shear testing has served as a fundamental laboratory choice for soil–geosynthetic interface testing, with the benefits being its availability, simplicity, and straightforward shear strength acquisition. This review paper pays attention to the direct shear testing and modelling of soil–geosynthetic interfaces. A brief laboratory interface experiment overview is presented, summarising the adopted soil–geosynthetic types, as well as the influences of various factors regarding soil–geosynthetic properties and loading/environmental conditions. Development of the finite element method to model interfaces is introduced, concentrating on the commonly adopted zero-thickness element, the thin-layer element, and continuum elements. As a result, emphasis is given to the comparison of the three element methodologies for the analysis of their advantages and limitations in accuracy, stability, and applicability for interface modelling. Based on the retrospective analysis, a summary and visions for the research progress of soil–geosynthetic interface testing and modelling are proposed to provide suggestions for future research topics.

CU test and CD test were performed to capture the stress-strain characteristics of the clay in Dongting Lake area, China. Since the classical constitutive model cannot ideally describe the strain hardening behavior of the clay, an improved constitutive model that involved three damage factors was proposed. The damage first factor , which represents elemental volume strength , was fitted by the Weibull function. The second and third damage factors and , which represent the porosity ratio and the drainage rate respectively, were fitted by Harris function. The CD test damage model is constructed by , , and . In the CU test, the porosity ratio is a constant value, and the drainage volume is 0, so that is constant value and is 0. Therefore, the CU test damage model of the clay was constructed using the damage first factor . In the end, the accuracy of the proposed CU/CD damage constitutive models of the clay was validated with the experimental results. It is found that the results fitted by the proposed methodology are in good agreement with the experimental results.