To investigate the effect of interface temperature on the soil-reinforcement interaction mechanism, a series of pullout tests were conducted considering different types of reinforcement (geogrid and non-woven geotextile), backfill (dry sand, wet sand, and clay), and six interface temperatures. The test results indicate that at interface temperatures of 0 degrees C and above, reinforcement failure didn't occur during the pullout tests, whereas it predominantly occurred at subzero temperatures. Besides, the pullout resistance for the same soil-reinforcement interface gradually decreased as the interface temperature rose. At a given positive interface temperature, the pullout resistance between wet sand and reinforcement was significantly higher than that of the clayreinforcement interface but lower than that of the dry sand-reinforcement interface. Compared with geotextile reinforcements, geogrids were more difficult to pull out under the same interface temperature and backfill conditions. In addition, the lag effect in the transfer of tensile forces within the reinforcements was significantly influenced by the type of soil-reinforcement interface and the interface temperature. Finally, the progressive deformation mechanism along the reinforcement length at different interface temperatures was analyzed based on the strain distribution in the reinforcement.

Understanding the mechanical behaviour of water ice-bearing lunar soil is essential for future lunar exploration and construction. This study employs discrete element method (DEM) simulations, incorporating realistic particle shapes and a flexible membrane, to investigate the effects of ice content, initial packing density, and gravitational conditions on lunar soil behaviour. Initially, we calibrated DEM model parameters by comparing triaxial tests on lunar soil without ice to physical experiments and the angle of repose simulations, validating the accuracy of our approach. Building on this, we conducted simulations on water ice-bearing lunar soil, examining stress-strain responses, shear strain, bond breakage, deviatoric fabric, and N-ring structures. DEM simulations demonstrate that increasing ice content from 0 % to 10 % elevates peak strength from 85 kPa to 240 kPa in loose samples and from 0.2 MPa to 1.62 MPa in dense samples. This strengthening aligns with microstructural stabilization evidenced by 5-ring configurations and narrowed branch vector distributions. Strain field analysis reveals greater deformation magnitudes in icy regolith, suggesting a trade-off between enhanced load-bearing capacity and reduced ductility. These quantified mechanical responses, including strength gain, structural stabilization, and strain localization, reveal the dual engineering implications of water ice in lunar soil.

Accurately modeling soil-fluid coupling under large deformations is critical for understanding and predicting phenomena such as slope failures, embankment collapses, and other geotechnical hazards. This topic has been studied for decades and remains challenging due to the nonlinear responses of geotechnical structures, which typically result from plastic yielding and finite deformation of the soil skeleton. In this work, we comprehensively summarize the theory involved in the soil-fluid coupling problem. Within a finite strain framework, we employ an elasto-plastic constitutive model with linear hardening to represent the solid skeleton and a nearly incompressible model for water. The water content influences the behavior of the solid skeleton by affecting its cohesion. The governing equations are discretized by material point method and two sets of material points are employed to independently represent solid skeleton and fluid, respectively. The proposed method is validated by comparing simulation results with experimental results for the impact of water on dry soil and wet soil. The capability of the method is further demonstrated through two cases: (1) the impact of a rigid body on saturated soil, causing water seepage, and (2) the filling of a ditch, which considers the erosion of the foundation. This work may provide a versatile tool for analyzing the dynamic responses of fluid and solid interactions, considering both mixing and separation phenomena.

Mesh-free methods, such as the Smooth Particle Hydrodynamics (SPH) method, have recently been successfully developed to model the entire wetting-induced slope collapse process, such as rainfall-induced landslides, from the onset to complete failure. However, the latest SPH developments still lack an advanced unsaturated constitutive model capable of capturing complex soil behaviour responses to wetting. This limitation reduces their ability to provide detailed insights into the failure processes and to correctly capture the complex behaviours of unsaturated soils. This paper addresses this research gap by incorporating an advanced unsaturated constitutive model for clay and sand (CASM-X) into a recently proposed fully coupled seepage flow-deformation SPH framework to simulate a field-scale wetting-induced slope collapse test. The CASM-X model is based on the unified critical state constitutive model for clay and sand (CASM) and incorporates a void-dependent water retention curve and a modified suction-dependent compression index law, enabling the accurate prediction various unsaturated soil behaviours. The integration of the proposed CASM-X model in the fully coupled flow deformation SPH framework enables the successful prediction of a field-scale wetting-induced slope collapse test, providing insights into slope failure mechanisms from initiation to post-failure responses.

Liquefaction resistance and post-liquefaction shear deformation are key aspects of the liquefaction behavior for granular soil. In this study, 3D discrete element method (DEM) is used to conduct undrained cyclic triaxial numerical tests on specimens with diverse initial fabrics and loading history to associate liquefaction resistance and post-liquefaction shear deformation with the fabric of granular material. The influence of several fabric features on liquefaction resistance is first analyzed, including the void ratio, particle orientation fabric anisotropy, contact normal fabric anisotropy, coordination number, and redundancy index. The results indicate that although the void ratio and anisotropy strongly influence liquefaction resistance, the initial coordination number or redundancy index can uniquely determine liquefaction resistance. Regarding post-liquefaction shear deformation, the above quantities do not dictate the shear strain induced after initial liquefaction. Instead, the mean neighboring particle distance (MNPD), a fabric measure previously introduced in 2D and extended to 3D in this study, is the governing factor for post-liquefaction shear. Most importantly, a unique relationship between the initial MNPD and ultimate saturated post-liquefaction shear strain is identified, providing a measurable state parameter for predicting the post-liquefaction shear of sand.

Hidden soil caves pose a serious threat to the stability and safety of subgrades. In this study, using the two-dimensional particle flow discrete element code, a total of eight subgrade models with circular soil caves of different dimensions, depths, and locations were established. Under self-weight and superimposed loading, the deformation characteristics of fill subgrade models, such as the evolution of displacement field and crack development process, were analyzed. The results show that under the self-weight, after the fill subgrade model of soil caves with diameters of 2 m, 4 m, 6 m, and 8 m is stable, the overlying soil layer of the soil cave corresponds to the transformation of slag falling, block falling, collapse and rapid collapse, respectively. The larger the dimension of the soil cave, the larger the number of cracks and damage areas, and the more prone the fill subgrade is to collapse. The superimposed load makes the fill subgrade compress from shallow to deep, significantly increasing the overall subgrade deformation, the number of cracks, and the development range. The evolution of the displacement field and crack propagation of the fill subgrade are also controlled by the buried depth and location of the soil cave. Whether the fill subgrade collapses is comprehensively controlled by the dimension and buried depth of the soil cave, the mechanical parameters of the soil layer, the load, and its scope of action. Thus, a comprehensive criterion of cylindrical collapse of the soil layer above the soil cave is constructed.

Permafrost, a critical global cryospheric component, supports subarctic boreal forests but is frequently disturbed by wildfires, an important driver of permafrost degradation. Wildfires reduce vegetation, organic layers, and surface albedo, leading to active layer thickening and ground subsidence. Recent studies using interferometric synthetic aperture radar (InSAR) have confirmed the rapid and extensive post-fire permafrost degradation, and have largely focused on short-term impacts. However, the longer-term post-fire permafrost deformation, potentially persisting for decades, remains poorly understood due to limited data. Here, we applied InSAR in North Yukon to detect deformation signals across multiple fire scars in the past five decades. Using a chronosequence (space-for-time substitution) approach, we summarize a continuous trajectory of post-fire permafrost evolution: (a) an initial degradation stage, characterized by abrupt subsidence up to 50 mm/year and gradually slowing over the first decade, with cumulative subsidence exceeding 100 mm locally; (b) an aggradation stage from approximately 15 to 30 years after fire, marked by ground uplift reaching 25 mm/year before gradually declining, compensating for the earlier subsidence; and (c) a stabilization stage beyond three to four decades, where permafrost nearly recovers to pre-fire conditions with indistinguishable deformation between burned and unburned areas. Notably, the rarely-reported uplift phase appears closely related to vegetation regeneration and fire-greening feedback that provide thermal protection, suggesting a critical mechanism of permafrost recovery. These findings provide new insights into the resilience of boreal-permafrost systems to wildfires and also underscore the importance of long-term InSAR monitoring in understanding permafrost responses to wildfires under climate change.

A series of finite element analyses, conducted on the basis of modified triaxial tests incorporating radial drainage, were carried out to investigate the lateral deformation and stress state characteristics of prefabricated vertical drain (PVD) unit cells under vacuum preloading. The analyses revealed that the inward horizontal strain of the unit cell increases approximately linearly with the vacuum pressure (Pv) but decreases non-linearly with an increase in the initial vertical effective stress (sigma ' v0). The variations in the effective stress ratio, corresponding to the median excess pore water pressure during vacuum preloading of the PVD unit cell, were elucidated in relation to the Pv and sigma ' v0 using the simulation data. Relationships were established between the normalized horizontal strain and normalized effective stress ratio, as well as between the normalized stress ratio and a composite index parameter that quantitatively captures the effects of vacuum pressure, initial effective stress, and subsoil consolidation characteristics. These relationships facilitate the prediction of lateral deformation in PVD-improved grounds subjected to vacuum preloading, utilizing fundamental preloading conditions and soil properties. Finally, the proposed methodology was applied to analyze two field case histories, and its validity was confirmed by the close correspondence between the predicted and measured lateral deformation.

The sulphated gravel embankment in seasonal frozen soil regions may experience deformation problems such as salt expansion, frost heave, and settlement under rainfall percolation conditions and changes in environmental temperature, affecting considerably its normal use. In response to these issues, relying on the renovation and expansion project of an international airport in northwest China, this paper used a self-designed temperature control testing device and conducted indoor constant temperature tests and freeze-thaw cycle tests using on-site natural embankment filling, and conducted numerical simulation tests using the COMSOL Multiphysics software programme. This paper investigated the characteristics of temperature variation, moisture, salt migration, and deformation of sulphated gravel in seasonal frozen soil regions under rainfall percolation conditions. The results indicated that under environmental temperature changes in the range of- 10-25 degrees C, the temperature at which sulphated gravel salt expansion and frost heave occur was approximately-8 degrees C, and the deformation sensitive depth range from 0 to 200 mm. The moisture and salt contents of soil samples would experience a sudden increase due to rainfall percolation, with the sudden increase in moisture in the soil sample with a salt content of 0.9 % lagging that of the soil sample with a salt content of 0.5 % by one freeze-thaw cycle. Rainfall percolation significantly enhanced the settlement deformation of sulphated gravel during freeze-thaw cycles. The primary causes of soil deformation include the upward migration of water vapour, the downward percolation of moisture, and rainfall. These factors contribute to the destruction of the soil structure and alter the contact modes between soil particles, resulting in soil loosening and settlement deformation.

Submarine landslides are a geological hazard that may cause significant damage, and are among the most serious problems in offshore geotechnics. Understanding the mechanism of submarine landslide/offshore structure interaction is essential for risk assessment, but it is challenging due to its complexities. In this study, ten centrifuge tests were conducted to determine how offshore wind turbines founded on four piles respond to consecutive submarine landslides. The tests highlighted two mechanisms of soil deformation and foundation settlement associated with the landslide cycle: (1) deformations of the clay were associated with induced excess pore water pressure, and increased with the number of landslides; and (2) by contrast, foundation settlements largely depended on the dynamic impact of the first cycle and remained unchanged for the remaining events. The settlements were 0.5 m for the 10 m pile foundation and about 0.1 m for the 20 m pile foundation, both in clay and in sand. It was also found that increasing pile length reduces the excess pore water pressure, soil deformation and foundation settlement.