This study evaluates dykes stability of bauxite residue storage facility using limit equilibrium (LEM) and finite element methods (FEM), considering diverse construction phases. In LEM, steady state seepage is simulated using piezometric line while factor of safety (FOS) is determined by Morgenstern-Price method using SLOPE/W. In FEM, actual loading rates and time dependent seepage is modelled by coupled stress-pore water pressure analysis in SIGMA/W and dyke stability is assessed by stress analysis in SLOPE/W, referencing SIGMA/W analysis as a baseline model. Both the analysis incorporated suction and volumetric water content functions to determine FOS. FEM predicted pore pressures are validated against in-situ piezometer data. The results highlight that coupled hydro-mechanical analysis offers accurate stability assessment by integrating stress-strain behaviour, pore pressure changes, seepage paths, and dyke displacements with time. It is found that inclusion of unsaturated parameters in Mohr-Coulomb model improved the reliability in FOS predictions.

The present document presents a review on the use of the finite element software package CODE_BRIGHT to simulate reinforced soil structures (RSS). RSS are composed of longitudinal steel or polymeric materials, placed orthogonal to the main stress direction in a soil mass, acting as tension-bearing elements. A common application of RSS is in retaining structures, in the form of reinforced soil walls (RSWs). RSW are usually designed with analytical methods, which have limited capabilities when predicting a structure's deformation response. To improve on this, the use of numerical tools allows to quantify the stress-strain response of complex, compound structures, such as RSWs. Several factors must be considered when modelling RSS, including reinforcement response, which can be non-linear under several circumstance (including time- and temperature-dependencies), soil-reinforcement interaction, soil-structure interaction, and soil response, all of which can be affected by the presence of moisture. Using laboratory measured data, the individual response of reinforcements (e.g., creep elongation), as well as the compound behaviour of soil-reinforcement material (e.g., pullout response) can be simulated to explore individual and compound response. Depending on the modelled phenomena, numerical simulations may include 2D and 3D representations. For full-scale reinforced soil walls, the stress-strain response within the soil mass, reinforcements, concrete facing panels, and connections can be studied in magnitude and distribution. Details regarding special considerations of how to model such structures with CODE_BRIGHT and other commercially available software are provided. Insights on the thermo-hydraulic repone of RSWs are covered. Advantages, limitations and future lines of research in the use of CODE_BRIGHT are explored.

In metropolitan cities, underground railway lines of Mass Rapid Transit Systems are the lifeline to the daily commuters. However, these underground lines cause vibrations while trains move. This ground-borne vibrations may cause damage to heritage buildings and fa & ccedil;ade elements. Humans can feel this vibration, and the comfort of people living nearby is compromised if vibrations cross threshold limit. In the current study, a two-stage coupled analysis is conducted to assess ground-borne vibrations in the free field generated by moving trains in a circular shaped tunnel. Two sub-models are generated-(a) train-track sub-model and (b) tunnel-soil coupling sub-model. The preceding model is a closed-form analytical solution which calculates the quasi-static effect of dynamic interactions between the train wheel and the railway track. The follower model is a 2D FE model to calculate the transfer of dynamic forces from track-tunnel interface to the ground surface through the soil medium. It is found that the computed results fairly match with experimental results for both amplitude and frequency content of the vibration. It is observed that ground vibrations reduce with distance from tunnel and any structure or residents staying beyond 30 m distance would not be affected by vibration as only 25% of vibration is present at this distance. The vibration is found to increase with velocity of train and at soft ground conditions to limit vibration, the velocity of train can be restricted. It is found that the frequency content of vibration is in interference range of human life and critical zone of frequency of structures. Therefore, careful assessment of vibration is required during finalization of the metro project particularly if the ground has shear wave velocity of less than 400 m/s.

The seismic excitations are potential hazards for offshore wind turbines located in earthquake prone zone. To investigate the dynamic characteristics of bottom-fixed offshore wind turbines (OWTs) under earthquakes, the influence of aerodynamic, hydrodynamic loads and pile foundation flexibilities is non-negligible. Hence, in this study, the fully coupled simulation tool FAST V8 for OWTs under earthquakes is updated based on the devised equations and the rotor-nacelle-assembly-tower-substructure numerical models considering different boundary conditions are established. The natural modes of a monopile substructure are compared to validate the accuracy of the established numerical model in the updated FAST V8. Subsequently, the OWT structural dynamic responses with different foundation boundary conditions under the combination of winds and waves, the combination of winds, waves, and earthquakes are analyzed and discussed, and a short-term damage equivalent load is adopted to assess the effect of pile foundation flexibility on OWTs. Finally, it is pointed out that the different foundation boundary constraint conditions have obvious influence on the OWT dynamic responses, especially for the model with coupled spring boundary condition under the action of earthquakes, the effect of second order frequency is more significant. In addition, the influence of different environmental loading frequencies on the OWT structure can also be observed.

This study compares the performance of various foundation systems in expansive soils, such as mats, granular anchor piles, and concrete piles. Expansive soils experience volumetric changes due to moisture fluctuations, which can lead to structural damage. Abaqus software, in conjunction with the SCV approach, is used to analyze soil-foundation interactions. A custom subroutine enhances simulation accuracy by incorporating empirical data on unsaturated clay behavior, matric suction, and variations in effective stress. The method's accuracy is validated by comparing simulation results to field and laboratory experiments. The findings indicate that increasing the applied load on mats decreases overall heave but increases the differential heave. Additionally, higher soil permeability dereases the differential heave of mats. Granular anchor piles outperform concrete piles by more than 50% in highly expansive soils, suggesting a preference for these foundations. This study provides insights into the behavior of expansive soils, which will assist engineers in designing resilient foundation systems for structures.

A soil-water-air fully coupled numerical framework is proposed to predict the deformation and hydraulic behavior of soils under different saturation states in response to dynamic loading. The proposed framework is developed based on the mixture theory of porous media and the governing equations are discretized with the finite-element method. The soil behavior is modeled by a sophisticated constitutive model. The hysteresis characteristic and the mutual dependence between volume change and the degree of saturation in the soil-water characteristic curve (SWCC) are considered. A consistent description for both unsaturated and saturated soils is achieved by taking the effective stress and the degree of saturation as the two independent variables, with only one set of unified mechanical/hydraulic parameters. The numerical framework is first validated at the element level against undrained and unvented strain-controlled cyclic triaxial test results of unsaturated Toyoura sand. The reliability of the proposed framework in addressing boundary value problems is further validated by the simulation of a dynamic centrifuge model test. The numerical framework is further applied to the dynamic stability analysis of unsaturated embankments with different initial water contents. The results show that initially unsaturated embankments with relatively high water content are susceptible to liquefaction during seismic loading. There is a significant correlation between the liquefaction and the deformation-induced soil saturation. Deformation-induced saturation initially occurs at the toe of the embankment and then gradually extends to the areas near the lateral surfaces of the embankment, which triggers the development of shear bands.

In this paper, a computational framework based on the Smoothed Particle Finite Element Method is developed to study the coupled seepage-deformation process in unsaturated porous media. Governing equations are derived from the balance laws of solid and fluid phases considering partial saturation effects in porous media. Moreover, an hourglass control method is implemented to avoid the rank-deficiency issue in SPFEM and the moving least squares approximation technique (MLS) is implemented to eliminate the pore pressure oscillations when the low-order triangle element is used. The proposed coupled SPFEM formulation is validated through four elastic examples and one elasto-plastic example. Good agreement with the numerical or analytical results reported in the literature is obtained. Further, the rainfallinduced slope failure is studied, in which a suction-dependent elasto-plastic Mohr-Coulomb model is adopted to take account of the suction effect in unsaturated soil. The evolution of the suction and soil deformation during the rainfall period and the whole slope failure process are obtained. It is demonstrated that the proposed method is a promising tool in numerical investigations of both the triggering mechanisms and post-failure behavior of the rainfall-induced slope failure.

Landslide dams consist of unconsolidated heterogeneous material and lack engineering measures to drain water and control pore water pressure. They may be porous and seepage through them could potentially lead to piping failure. In this research, the internal processes within a long-existing landslide dam are assessed under transient seepage force. The implemented approach includes a 3D finite element numerical simulation executing fully coupled flow-deformation and consolidation methods based on hydraulic data measurements and geotechnical laboratory tests. The nonlinear constitutive model 'Hardening Soil' is applied to accurately calculate the stressinduced pore water pressure, effective stress, deformation, and flow. Further, the possibility of slope failure due to seepage force is investigated through the strength reduction method. The results highlight the dependency of the seepage flow on the corresponding variation of the relative permeability and saturation in the soil mediums under different rates of seepage force. Small rates of seepage force, however, impose deformation at the dam's crown. High effective stress is obtained at negative small rates of seepage force where the long duration of fluctuation is modeled. In the drawdown simulation, there is a reverse relation between effective stress and the rate of the seepage force. Through the modeling process and based on the measured data, two seepage paths are detected within the landslide dam, while their activation depends on the lake level. The modeling approach and the required data analysis are suggested for utilization in further studies regarding the seepage process understanding at the long-existing landslide dams and their hazard assessments in addition to the common geomorphological approaches.

Engineering practices indicate that stratum hydraulic conductivity (SHC) has a significant influence on deep excavations. However, this influence has been ignored in previous studies with undrained analyses. In this study, a numerical model, combined with the verified hydromechanical coupled method, is established to investigate the effect of SHCs on the performances of deep excavations. Excavation deformation, pore-water pressure, lateral pressure, and the stress evolution process are presented, respectively, to illustrate these influences. In addition, the model of a beam on an elastic foundation is employed to interpret the influential mechanism of SHCs on excavation deformations. Analysis results indicate that excavation deformations increase significantly with the increase in SHCs from 1 x 10-7 to 1 x 10-5 cm/s (i.e., the range of SHCs of soil containing silt). The influence of SHCs on excavation deformations is mainly attributed to the variation of effective stress levels on the excavated side. As SHC increases, the change in the resultant force of the total stress acting on the retained side of the wall, as loads, can be ignored, while the resultant force of the effective stress acting on the excavated side of the wall, as resistances, decreases dramatically. These findings emphasize the importance of accurate determination of the SHC of strata containing silt. Engineering practices indicate that stratum hydraulic conductivity (SHC) significantly affects the performances of deep excavations in Shanghai soft deposits. Constructions in the first aquitard (AdI) have been involved in the many deep excavations in Shanghai, China, and therefore, identifying the effects of the SHC of AdI on deep excavations can further ensure the safety of constructions. In this study, it is found that excavation deformations increase significantly as the SHC of AdI increases from 1 x 10-7 to 1 x 10-5 cm/s (i.e., the SHCs in soil containing silt). This finding indicates that valuing the SHC of AdI containing silt requires utmost caution, and adopting appropriate methods such as dewatering can significantly decrease excavation deformations.

Immense liquefaction damage was observed in the 2011 off the Pacific coast of Tohoku Earthquake. It was reported that, in Chiba Prefecture, Japan, the main shock oozed muddy water from the sandy ground and the aftershock which occurred 29 min after the main shock intensified the water spouting; thus, the aftershock expanded the liquefaction damage in the sandy ground. For comprehending such a phenomenon, using a soil-water-air coupled elastoplastic finite deformation analysis code, a rise in groundwater level induced by main shock is demonstrated, which may increase the potential of liquefaction damage during the aftershock. The authors wish to emphasize that these results cannot be obtained without soil-water-air coupled elastoplastic finite deformation analysis. This is because the rise in groundwater level is caused by the negative dilatancy behavior (plastic volume compression) of the saturated soil layer which supplies water to the upper unsaturated soil layer, and it is necessary to precisely calculate the settlement of ground and the amount of water drainage/absorption to investigate the groundwater level rise. This study provides insight into the mechanism of ground liquefaction during a series of earthquakes.