Excavation-induced retaining wall deflection (RWD) significantly influences the safety of surrounding built environment. To predict the three-dimensional RWD in heterogeneous strata, a new partial differential equation (PDE) is derived in this study, and two prediction models are proposed, i.e. the physics-informed neural network (PINN) model and the data-driven PINN model. As a physical constraint, the new PDE is crucial to the loss functions of these models. Then, the validity of the models is verified and analysed using a subway deep-foundation pit. The results show that the training times of both models are controlled within 900 s, which is a significant reduction compared to that of the conventional numerical model. In addition, the prediction accuracy of the data-driven PINN model is higher than that of the numerical model, while that of the PINN model is slightly lower than that of the numerical simulation. However, in contrast to the data-driven PINN model, the PINN model can identify irregular soil interfaces in heterogeneous strata to learn the deflection continuity conditions at irregular interfaces and realize RWD prediction in non-uniform distributed strata. In practical applications in foundation pit engineering, the selection of the PINN and data-driven PINN models can be conducted according to the in situ distribution conditions of the strata to enable the early prediction of potential RWD, thereby providing a reliable basis for the further optimisation of retaining structures design.

Compacted bentonite blocks are proposed for buffer barriers in deep geological repositories for high-level radioactive waste (HLRW) disposal. These blocks, manufactured through uniaxial compression in molds, exhibit heterogeneity that may impact long-term buffer performance. This study focuses on the physical and hydro-mechanical heterogeneity of full-scale blocks induced by the compaction process. Sector-shaped blocks, with radii of 600 mm and 1200 mm and a height of 200 mm, were axially compressed. Key parameters, including water content, dry density, elasticity modulus, swelling pressure, and permeability, were measured to assess the heterogeneity. Results show that the heterogeneity in the upper layer is primarily caused by differences in drainage and gas expulsion pathways. As depth increases, water content and dry density become more correlated. Hydro-mechanical behavior is largely controlled by dry density, but its fluctuation ratio is much higher than that of dry density. Regarding the microstructure, pore structure heterogeneity follows the order: corner regions > edge regions > center regions, and upper layer > middle layer > lower layer. Vertical microcracks also develop to varying degrees, increasing the anisotropy of the blocks. Upon these observations, the study thoroughly discusses the feasibility and challenges of reckoning the hydro-mechanical properties of blocks using dry density distribution alongside laboratory-scale data. Additionally, it proposes an indicator to evaluate the overall heterogeneity of buffer blocks. These findings highlight the inherent heterogeneity of compacted bentonite blocks at the engineering scale, providing valuable insights for future experiments and simulations.

In the natural environment, the soil structure can be weakened by temperature fluctuations and climatic changes. Nevertheless, the dynamic behavior of expansive soils, especially those with high swelling and pronounced fissure properties, subjected to wetting-drying-freeze-thaw (WDFT) cycles has been rarely investigated. Undisturbed and remolded samples, made of Xinjiang's highly expansive soils, were evaluated in this study through comprehensive resonant column tests conducted at several confining pressures and WDFT cycles. A typical hyperbolic model demonstrated the decay law of shear modulus with strain. An estimated model of the maximum shear modulus, incorporating the two factors, was developed, and it was found to be in good agreement with the measurement results. The results reveal that strain, WDFT cycle, and confining pressure have qualitatively uniform effects on the shear modulus of natural soils containing fissures and recompacted samples. However, the maximum shear modulus of the undisturbed samples is lower by 0.83-13.24 MPa due to the presence of initial fissures, except for the confining pressure of 400 kPa. Also, their responses to confining pressure are more significant, with the shear modulus increased by up to 20 %-124 % relative to that at 25 kPa. Furthermore, the relative difference in the shear modulus (up to about 60 %) between the two samples tested under low confining pressure conditions deserves special attentions. The quantitative differences in shear modulus and cumulative damage effect of the tested samples are attributed to the initial fabric and microstructural evolution, as observed by Scanning Electron Microscope (SEM). This research enriches the theoretical framework for analyzing the ability of soils to resist shear deformation under small strain, which is instructive for disaster prevention and mitigation in expansive soil regions, considering the effects of climate change.

Stratigraphic interface characterization and strength parameter assessment of geomaterials constitute fundamental research priorities in geological and geotechnical engineering. While measurement while drilling (MWD) and drilling process monitoring (DPM) have emerged as critical techniques for acquiring real-time drilling parameters, inherent limitations in data interpretation persist. The critical challenge of random fluctuations in MWD-derived penetration rate measurements exhibits poor correlation with the stratified homogeneity characteristics of geological formations. Such discrepancies undermine the reliability of stratigraphic classification and mechanical property analysis. Through systematic comparison of MWD and DPM datasets combined with quantitative parameter evaluation, this investigation reveals significant methodological distinctions in data acquisition accuracy. Machine learning-enhanced analysis employing Support Vector Machine (SVM) algorithms demonstrates that DPM-derived parameters provide superior stratigraphic identification capabilities. Our findings indicate that DPM implementations achieve 20.57 % and 38.01 % higher resolution in interface detection along two drill-holes compared to the conventional MWD approaches. This improvement allows for better prediction of stratigraphic profiles and more precise guidance in subsequent geological and geotechnical engineering practices.

Traditional active earth pressure evaluations considering seepage are typically deterministic, assuming uniform soil layers. However, soil hydraulic properties exhibit the obvious spatial variability due to geomorphological processes or poor construction control. To address this, the random limit analysis method (RLAM) is employed to investigate the influence of spatial variability of saturated hydraulic conductivity on active earth pressure. To combine random field simulations with the limit analysis-based evaluation method, this study discretizes the conventional three-dimensional (3D) rotational failure mechanism. Owing to the energy dissipation principle, the explicit expression of 3D active earth pressures can be derived. The proposed method's validity is demonstrated through comparisons with available analytical solutions, deterministic numerical calculations, and random finite difference method (RFDM). RLAM integrating with Monte Carlo simulations (MCS) in MATLAB, facilitates the probabilistic analysis of the active earth pressure to be evaluated. The findings indicate that the present method not only incorporates the spatial variability of hydraulic properties, but also enhances the computational efficiency of calculating active earth pressures compared to the RFDM. Based on extensive uncertainty analyses, this study proposes a system reliability evaluation method for semi-gravity retaining walls, accounting for the spatial variability of saturated hydraulic conductivity. The results reveal that under different random field design scenarios, all decay curves of system failure probabilities for a semi-gravity retaining wall intersect within a specific range, referred to herein as the "turning region". Furthermore, as the normalized horizontal autocorrelation distance, anisotropic ratio and coefficient of variation increase, the effective influence zone of the wall design index on system failure probability gradually expands, offering valuable guidance for the design and construction of semi-gravity retaining walls.

The actively-heated fiber-optic (AHFO) method can near-continuously measure soil water content along the AHFO sensors by sensing the temperature variation during an actively heated pulse. Different heating materials, structures, and fiber-optic temperature sensing techniques significantly impact the measurement performance of AHFO sensors. However, there has been no systematic evaluation regarding the measurement performance of soil water content by different AHFO sensors. To address this issue, this study focuses on the measurement performance and monitoring potential of six different AHFO sensors (i.e. actively-heated fiber Bragg grating (AH-FBG) alundum tube, AH-FBG cable, carbon fiber heated cable (CFHC), copper metal heated cable (CMHC), CFHC sensing tube, and CMHC sensing tube). Numerical models were built first for simulating the thermal response process of six AHFO sensors to quantify the measurement accuracy and sensitivity of soil water content. Then, the in situ applications of six AHFO sensors were carried out in Yan'an, China. The numerical and in situ monitoring results indicate that the measurement accuracy and sensitivity of soil water content are both highest by using CFHC sensing tube and CMHC sensing tube. CMHC sensing tube is most suitable for fine and accurate monitoring of in situ soil, while AH-FBG alundum tube and AH-FBG cable are best suited for long-term real-time remote monitoring. In practical applications, it is recommended that geotechnical engineers, when selecting AHFO sensors for a specific site project, should take into account a variety of factors, including measurement performance, spatial resolution, monitoring duration, site installation, and power supply conditions.

This study investigates particle crushing mechanisms in granular soils during shearing through staged triaxial compression experiments performed at prescribed axial strains and varying confining stresses, integrating a high-performance acoustic emission (AE) measurement system. The study analyzed particle crushing-related parameters using grain size distribution (GSD)-based indices (relative breakage index B_r and its rate ΔB_r) and AE-based parameters (high-frequency AE hits and hit rates ). The results confirm the feasibility of high-frequency AEs (>100 kHz) in comprehensive quantification of particle crushing, with a strong linear relationship observed between and B_r. Significant particle crushing occurs within the initial 5 % of axial strain, which correlates with the yielding and peak-stress phases. This process yields fragments with a size range of 0.425-2 mm. Increased confining stresses result in a steady rise in B_r and , suggesting that large strains are required for stable particle grading. The evolution trends of different high-frequency AE ranges reveal a shift to complex crushing mechanisms, such as particle abrasion/grinding and corner breakage/particle splitting, highlighting the role of stress and strain levels in influencing particle damage behavior.

Supersulfated cement (SSC) is considered an environmentally friendly alternative to ordinary Portland cement (OPC), while its stabilization efficiency on dredged sediment (DS) is still unclear. Three types of SSC were prepared by combining ground granulated blast-furnace slag, alkali-activator NaOH, and a sulfate waste source, yielding SSCE (from electrolytic manganese residue), SSCP (from phosphogypsum), and SSCD (from desulfurization gypsum). To further enhance the stabilization efficiency of SSC on DS, nano-SiO₂ (NS) and nano-Al₂O₃ (NA) were incorporated individually and as a composite blend. Mechanical properties and microstructural analyses were conducted to evaluate the stabilization efficiency and elucidate the underlying mechanisms. The leaching toxicity of SSCE-stabilized DS was investigated via leaching tests. The results showed that both alkali-activation and nano-modification can significantly improve the strength development of SSC-stabilized DS. At least 15 % NaOH was required for SSC to achieve the same stabilization efficiency as OPC. The optimum NA-modified SSCD-stabilized DS demonstrated superior strength compared to OPC-stabilized DS. Composite NS/NA-modification was more efficient than using NS or NA individually. For DS stabilized with SSCE, SSCP, and SSCD, the optimal NS-to-NA mass ratios were 7:3, 3:7, and 3:7, respectively. Notably, the nano-modified SSCE-stabilized DS showed no environmental risks. Incorporating NS and NA into SSC-stabilized DS respectively promoted the formation of C-S-H gel and ettringite. A micro-mechanism model was developed to explain the strength evolution of nano-modified SSC-stabilized DS. This study provides a theoretical basis for the application of SSC in DS stabilization, and facilitates the collaborative resource utilization of industrial solid wastes and DS.

Callovo-Oxfordian (COx) claystone has been selected as the host rock formation for the deep geological disposal of radioactive waste in France, called the Cigéo project. The excavation of drifts in the COx formation induced damage zones with an anisotropic shape, while the stress state around the drifts is almost isotropic. This is due to the anisotropic properties of the host rock formation and the instability caused by the brittle damage. In this study, the mechanical anisotropy of COx claystone was investigated through a triaxial shear test, where the axial stress was maintained while the lateral stress was decreased. Such a method was proposed for simulating one of the possible unloading paths involved during the excavation. The triaxial samples were prepared along different directions based on the angle between the axial loading direction and the one perpendicular to the bedding plane. Results show that the stress-strain curve exhibited an elasto-plastic pattern. With increasing deviatoric stress, a minor decline in Young's modulus E was observed, suggesting progressive damage behaviour. The shear strength changed with increasing the loading angle, showing the anisotropic property of COx claystone. Moreover, the results in this study and collected from other works show a time-dependent behaviour of COx claystone. It is attributed to the coupled effect of creep and pore pressure dissipation inside claystone.

Landfill cover system plays a crucial role in reducing leachate generation by limiting rainwater infiltration. This paper evaluates the field performance of a polymer-enhanced three-layer cover system at a leather sludge dump site in Xinji city, China over a 1-year monitoring period. Waste soil (WS), sand-bentonite mixture (SB), and sand-polymer-bentonite mixture (SPB) were used as the low-permeability layer, respectively, in three test areas, above which the fine-grained cultivated soil and gravel were used in the top and middle layers to form a capillary barrier. During the 1-year monitoring period, the recorded cumulative rainfall was 452.1 mm, and the volumetric water content (VWC) at the top layer fluctuated significantly from 0.13 to 0.45 in response to rainfall and evaporation, but that of the low-permeability layer maintained stable for both cover SB and SPB. No water percolation was detected during the 1-year monitoring period. Furthermore, numerical simulations were carried out to assess the anti-seepage performance under more extreme climatic conditions (i.e., higher rainfall intensity and long-term deterioration of soil permeability). Numerical simulations corroborated the field observations that the SPB layer effectively minimized percolation even under extreme climatic conditions. For example, under the most unfavourable conditions, the computed annual percolation through the cover SPB was 4.7 mm, as low as 27.2% and 8.1% that through the cover SB (=17.3 mm) and WS (=57.9 mm). Overall, the results suggest that the polymer-enhanced three-layer soil cover is a promising alternative to traditional geomembrane-based covers and/or thick composite soil covers.