Acta Geotechnica最新文献

The evaluation of thermo-hydro-mechanical (THM) coupling response of clayey soils has emerged as an imperative research focus within thermal-related geotechnical engineering. Clays will exhibit nonlinear physical and mechanical behavior when subjected to variations in effective stress and temperature. Additionally, temperature gradient within soils can induce additional pore water migration, thereby resulting in a significant thermo-osmosis effect. Indeed, thermal consolidation of clayey soils constitutes a complicated THM coupling issue, whereas the theoretical investigation into it currently remains insufficiently developed. In this context, a one-dimensional mathematical model for the nonlinear thermal consolidation of saturated clay is proposed, which comprehensively incorporates the crucial THM coupling characteristics under the combined effects of heating and mechanical loading. In current model, the interaction between nonlinear consolidation and heat transfer process is captured. Heat transfer within saturated clay is investigated by accounting for the conduction, advection, and thermomechanical dispersion. The resulting governing equations and numerical solutions are derived through assuming impeded drainage boundaries. Then, the reasonability of current model is validated by degradation and simulation analysis. Subsequently, an in-depth assessment is carried out to investigate the influence of crucial parameters on the nonlinear consolidation behavior. The results indicate that increasing the temperature can significantly promote the consolidation process of saturated clay, the dissipation rate of excess pore water pressure (EPWP) is accelerated by a maximum of approximately 15%. Moreover, the dissipation rate of EPWP also increases with the increment of pre-consolidation pressure, while the corresponding settlement decreases. Finally, the consolidation performance is remarkably impacted by thermo-osmosis and neglecting this process will generate a substantial departure from engineering practice.

Granular soil generally exhibits an anisotropic stiffness in engineering but challenging to quantify in situ and laboratory condition, due to a lack of the appropriate factor and quantitative research. In this paper, discrete element method is employed to create two typical types of soil fabric and conduct shear wave measurement in double direction, with the microscopic parameters monitored to investigate the connection with macroscopic stiffness anisotropy. The results show that the reference fabric increases as fabric anisotropy increases first and then decreases with further increase in the XZ stress plane, while always decreases approximately linearly in the XY stress plane. The reference fabric is determined by the contact density in the direction of wave propagation and particle perturbation under microscale examination. The results also reveal a linear relationship between the macroscopic stiffness anisotropy and microscopic fabric anisotropy, which could be used as an effective method to reflect the degree of anisotropy in situ by wave measurement. And the applicability of the expression of small-strain shear modulus is also discussed.

Internal erosion is one of the most important factors that cause earth structures that retain water, such as embankment dams, to collapse. Concentrated leak erosion, one of the forms of internal erosion, occurs in cracked fine-grained soils and pressurized flow conditions. To evaluate the concentrated leak erosion risk of cracks/voids, it is necessary to ascertain the erosion resistance of these materials. The erosion rate and critical shear stresses determine internal erosion resistance in concentrated leak erosion. This study determined soil’s concentrated leak erosion resistance using test equipment that allowed the flow to pass through a hole with stress-free (no loading), anisotropic-compression stress, anisotropic-expansion stress, and isotropic stress conditions. The stresses that developed in the samples’ hole wall where erosion occurred were determined with numerical modeling as pre-experimental stress conditions. The experiments were performed under a single hydraulic head on four selected cohesive soils with different erosion sensitivity. Time-dependent flow rates obtained from the test system can be used to determine hydraulic parameters, such as energy grade lines, with the help of basic theorems of pipe hydraulics in theoretical hydraulic models. Moreover, the erosion rates were quantitatively determined using the continuity equation, while critical shear stresses were qualitatively compared for concentrated leak erosion developed by the dispersion mechanism. As a result of the experiments, stress conditions influence the concentrated leak erosion resistance in the soil samples with dispersive erosion. Moreover, the shear strength in the Mohr–Coulomb hypothesis can explain the erosion resistance in these soils under stress conditions depending on the sand/clay ratio.

Rainfall-induced landslides have caused a large amount of economic losses and casualties over the years. Machine learning techniques have been widely applied in recent years to assess landslide susceptibility over regions of interest. However, a number of challenges limit the reliability and performance of machine learning-based landslide models. In particular, class imbalance in the dataset, selection of landslide conditioning factors, and potential extrapolation problems for landslide prediction under future conditions need to be carefully addressed. In this work, we introduce methodologies to address these challenges using XGBoost to train the landslide prediction model. Data resampling techniques are adopted to improve the model performance with the imbalanced dataset. Various models are trained and their performances are evaluated using a combination of different metrics. The results show that synthetic minority oversampling technique combined with the proposed gridded hyperspace sampling technique performs better than the other imbalance learning techniques with XGBoost. Subsequently, the extrapolation performance of the XGBoost model is evaluated, showing that the predictions remain valid for the projected climate conditions. As a case study, landslide susceptibility maps in California, USA are generated using the developed model and are compared with the historical California landslide catalog. These results suggest that the developed model can be of great significance in global landslide susceptibility mapping under climate change scenarios.

Calcareous sand–diatom mixtures are found naturally in the coral reef sediments, where the diatom potentially affects the mechanical behaviors of the mixtures. We performed a series of isotropic compression and triaxial drained shear tests to investigate the effect of diatom on the compression and critical-state behaviors of the mixtures. We found that the diatom and effective confining pressure can considerably affect the compression index, swelling index, coefficient of volume compressibility, compression modulus, secant modulus, peak-state deviatoric stress, peak-state axial strain, and peak-state frictional angle. In addition, the critical-state friction angle is independent of the diatom content, while the critical-state line (CSL) in the compression plane is affected significantly by the diatom content. We proposed modified equations for compression modulus and CSL considering the influence of diatom content, and the two equations could reasonably predict the compression deformation and critical-state behaviors of the mixtures. This study provides experimental basis for understanding critical-state behavior for the calcareous sand–diatom mixtures.

Suffusion is a typical type of internal erosion that is an important factor leading to the failure of dams and dikes. In this paper, fine particles are divided into erodible particles and non-erodible particles, and the soil suffusion mechanism is investigated by laboratory tests and CFD_DEM simulations when the content of erodible particles (F_c) and non-erodible particles (F_z) is 15% and 5%, 10% and 10%, and 5% and 15%. The global mean permeability coefficient (k_av) and local permeability coefficient (k_i–j) were calculated by monitoring the water head in the seepage path of the sample. The results show that with increasing non-erodible particle content, the difficulty of soil suffusion increases gradually. When soil suffusion occurs, the loss of fine particles starts from the seepage outlet area and the influent area, and the non-erodible particles have little influence on the particle loss process in these two areas. After the occurrence of suffusion, the number of weak contact chains is obviously reduced, while the strong contact chains are basically stable. When F_z = 5% and F_z = 10%, the average permeability coefficient of the soil after suffusion expands to 2.21–1.60 times that of the initial state, and the corresponding values of the CFD_DEM simulation are 2.14–1.86 times.