As a potential source of damage, earthquake-induced liquefaction is a major concern for embankment safety and serviceability. Densification has been a popular method for improving the performance of liquefiable soils. Understanding embankment settlement mechanisms plays a fundamental role in determining densification remediation. In this work, nonlinear dynamic analysis of embankments on liquefiable soils is conducted by the finite-difference program FLAC3D (version 6.0) with the simple anisotropic sand constitutive model. Numerical models are validated via dynamic centrifuge test results reported in the literature. The effects of densification countermeasures on the mean and differential settlements are explored in this study. Furthermore, the effects of the densification spacing and width are investigated to optimize the geometry of the densified regions. The development of pore pressure and the movement of the surrounding loose soil are discussed. The results show that both the mean settlement and differential settlement should be simultaneously utilized to comprehensively assess the overall effectiveness of densification treatment. The mean settlement is influenced by the densification spacing and width, but the differential settlement is highly associated with the inner edge of the densified region. This study provides insight for improving the design of the location and lateral extent of densification regions to prevent excessive embankment settlement.

Continuous internal erosion, commonly manifested as piping, is a major cause of failure in earthen structures. This study employs the hole erosion test to examine the internal erosion resistance of zein biopolymer-treated soil, encompassing three sandy soil types with varying particle sizes. The gelation mechanism of the zein binder is evaluated through rheological and shear wave analyses. Treated and untreated specimens are subjected to hydraulic gradients at constant flow rates. The erosion analysis focuses on changes in axial diameter, particle loss rate, shear stress, and erosion rate. The biopolymer gel demonstrates evolving rheological behaviour, transitioning from shear thickening to shear thinning after a 4-hour curing period. Treated specimens exhibit improved shear stress and erosion rate over time, which vary with particle sizes. Hydraulic shear stress decreases with the curing period, and particle size increases, correlating with erosion rate reduction. Higher consistency index of the biopolymer gel leads to decreased hydraulic shear stress, influenced by gel internal friction. Hydraulic shear stress linearly relates to shear wave velocity of the treated specimen. Zein biopolymer enhances erosion resistance of cohesionless sand through gel internal friction and treated specimen shear stiffness.

The presence of cracks significantly impacts the hydrological behaviour of clay embankments. This study aimed to enhance understanding of the complex interplay between the amount and propagation of desiccation cracks and seasonal variations. A full-scale embankment was constructed and equipped with an array of instruments, including pore water pressure, volumetric water content (VWC), and crack observer. The results suggested that continues cracks at shallow depths (0.5 m) exhibit significant seasonal fluctuations due to pronounced soil-atmosphere interactions, facilitating rapid water movement and substantial changes in crack width. In contrast, discontinuous cracks at intermediate depths (0.5 m) are less affected by seasonal changes, but they can propagate and connect over time due to repeated wetting and drying cycles. The crack intensity factor (CIF) above 0.4 m is highly sensitive to climatic variations, leading to pronounced fluctuations with changes in rainfall and dry conditions. The twofold increase in CIF values leads to a significant reduction in VWC (by 13.5%) at the depth of 0.25 m under the same atmospheric water balance. However, this effect is less pronounced at greater depths, such as 0.5 m, as discontinuous cracks are less effective in facilitating rapid drainage and moisture loss.

This study presents two large-scale model tests to investigate the load transfer mechanism of floating pile-supported embankments subjected to cyclic loading. The soft soil and piles were prepared using Kaolin clay and reinforced concrete. Results on cumulative settlements, pile efficacy, and strain distribution were obtained and analyzed under semi-sinusoidal cyclic loading. The results show that the floating pile increased surface settlement by 7.1% compared to the end-bearing pile-supported embankment. The soil arching in floating pile-supported embankment does not degrade under cyclic loading but slowly enhances with settlement development. Floating piles result in less arching, membrane effect, and pile strain.

During rainfall, collapse compression predominates due to the slippage of particles, resulting in the rearrangement of soil fabric toward a configuration dependent on the fabric of the initial stress state. Consequently, these alterations in soil fabric induce anisotropic mechanical behavior in unsaturated soils. In this study, an anisotropic model, denoted as ABBM and based on the Barcelona Basic Model (BBM), was implemented into FLAC to analyze the wetting behavior of a typical compacted embankment during infiltration. The research findings indicate that prolonged rainfall durations result in the evolution of the yield surface, consequently amplifying vertical surface displacement. Moreover, as the anisotropic evolution parameter surpasses a defined threshold, the degree of anisotropy diminishes, ultimately resembling the isotropic behavior observed in the Barcelona Basic Model (BBM) due to changes in preconsolidation pressure. The study presents an innovative approach to evaluate embankment performance under rainfall-induced conditions by considering changes in fabric anisotropy relative to the degree of saturation. The results demonstrate that alterations in the degree of saturation lead to rotation of the yield surface, nearly erasing anisotropy upon reaching full saturation. To account for parameter variability, a reliability analysis was performed using the Monte Carlo method, assessing the performance of embankment using different constitutive models, viz, the Mohr-Coulomb model, BBM, and ABBM. Notably, the analysis revealed that embankment failure probabilities simulated using the ABBM exceed those obtained using the Mohr-Coulomb criterion or BBM, suggesting a greater susceptibility to failure in terms of deformations. This observation has practical significance in a sense that use of appropriate constitutive models in embankments is required.

Seismic risk expresses the expected degree of damage and loss following a catastrophic event. An efficient tool for assessing the seismic risk of embankments is fragility curves. This research investigates the influence of embankment's geometry, the depth of rupture occurrence, and the underlying sandy soil's conditions on the embankment's fragility. To achieve this, the response of three highway embankments resting on sandy soil was examined through quasi-static parametric numerical analyses. For the establishment of fragility curves, a cumulative lognormal probability distribution function was used. The maximum vertical displacement of the embankments' external surface and the fault displacement were considered as the damage indicator and the intensity measure, respectively. Damage levels were categorized into three qualitative thresholds: minor, moderate, and extensive. All fragility curves were generated for normal and reverse faults, as well as the combination of those fault types (dip-slip fault). Finally, the proposed curves were verified via their comparison with those provided by HAZUS. It was concluded that embankment geometry and depth of fault rupture appearance do not significantly affect fragility, as exceedance probabilities show minimal differences (<4%). However, an embankment founded on dense sandy soil reveals slightly higher fragility compared to the one founded on loose sand. Differences regarding the probability of exceedance of a certain damage level are restricted by a maximum of 7%.

This research focuses on soils derived from volcanic ash in the city of Popayan, stabilized with low percentages of cement. The results reveal high variability in properties due to changes in moisture content, structural condition, and curing time. The study involved evaluating the physical and mechanical properties in both natural state and after modification with cement at 3%, 4%, and 5%. Natural state soils exhibit deficient conditions, such as subgrades or embankments, necessitating improvement in various cases. When cement is used as a stabilizer, it is possible to conclude that there is an increase in mechanical strength and marginal improvements in hydraulic properties (cement- modified soil). However, these improvements are not comparable to the significant enhancements observed after reaching a 5% cement content (soil-cement).

The mechanical behaviour of Fibre-reinforced sands (FRS) has been extensively studied, presenting improved mechanical properties compared to unreinforced soils. Many models have been developed to predict its general stress-strain behaviour. However, the use of double-phase models in FRS is still incipient. Double-phase models are advantageous because they can simulate the whole FRS and the behaviour of its individual components, soil skeleton and reinforcement. This paper uses a modified model for Municipal Solid Waste to reproduce the FRS mechanical response. Introducing a new hardening parameter and a dilatant zone allowed the model to reproduce FRS dilatancy. The model's variables are easily understood, allowing the reproduction of the mechanical behaviour of FRS formed by sands with void ratios ranging from 0.610 to 0.917 and mean grain size from 0.29 to 0.83 mm. The fibres' lengths varied from 12.5 to 51 mm. The results of triaxial and hollow cylinder torsional tests under different stress paths had their main characteristics (peak strength, post-peak behaviour, dilatancy and reinforcement effectiveness) well captured by the model. Predicted and experimental FRS's deviator stress usually differ by less than 15% and the model performance is equivalent or superior to other available models, even requiring fewer input parameters.

Basal reinforcement of embankments and supporting with piles is one of the most recent solutions for rapid embankment construction on soft foundation soils. This paper uses the Particle Image Velocimetry (PIV) to evaluate the performance of unreinforced and reinforced embankments over soft foundation soils in terms of maximum settlement at the embankment base, lateral displacements of the embankment toe and the strains in the reinforcement layer using the digital images captured during the centrifuge model tests at 40g. The reinforcement consisted of a single layer of a scaled-down model basal geogrid and additional support from end-bearing or floating piles. The paper examines the effect of varying embankment heights on the geogrid strains and deformation characteristics of subsoil under rapid embankment construction over unreinforced and reinforced soft foundation soil with varying support conditions. The unsupported reinforced embankments showed a peak geogrid axial strain near the toe, whereas it peaked near the mid- of the embankment for pile supported reinforced embankments. The study also investigates the failure mechanisms of unreinforced and reinforced embankments, with and without pile support, using shear strain contours derived from PIV analysis. The paper underscores the efficacy of PIV as a tool for visualising the deformation behaviour and failure mechanisms in soil during centrifuge model studies. Additionally, the research provides insights into the operation of an in-flight sand hopper used for embankment construction in centrifuge model studies. Post-investigation studies contribute to understanding the potential failure mechanisms in embankments supported by end-bearing and floating piles. Overall, this paper showcases the practical application of PIV in studying the challenges related to rapid embankment construction on soft foundation soils.

Pile-supported embankments are typically composed of soil-rock mixtures. within these structures, while the soil arching effect is crucial for effective load transfer, it remains incompletely understood, particularly when the impact of various loading conditions needs to be considered. This study investigates this problem using a 1 g physical experimental modeling approach. Subsequently, a DEM model for a full-scale pile-supported embankment of high-speed railways, accounting for multiple pile interactions, is established with proper model calibration. Numerical simulations are conducted to explore the load transfer mechanism and soil arching processes under self-weight, embankment preloading, and train-induced dynamics influences. The findings indicate that under self-weight, fully developed soil arching structures can be achieved with a sufficiently high embankment height, although they can diminish as the soil-pile relative displacement increases. However, during embankment preloading processes, represented by static loading, pressure can be transferred from pile caps to subsoil regions, potentially compromising the integrity of soil arching structures. Train-induced dynamics effects are modeled as cyclic loading inputs, revealing that an increase in loading frequency leads to weakened dynamic pressure fluctuation for both pile caps and subsoil regions, with a limited impact on the valley values of the pressures. Additionally, a higher loading frequency corresponds to smaller accumulated loading plate settlements.