The Arctic has been warming much faster than the global average, known as Arctic amplification. The active layer is seasonally frozen in winter and thaws in summer. In the 2017 Arctic Boreal Vulnerability Experiment (ABoVE) airborne campaign, airborne L- and P- band synthetic aperture radar (SAR) was used to acquire a dataset of active layer thickness (ALT) and vertical soil moisture profile, at 30 m resolution for 51 swaths across the ABoVE domain. Using a thawing degree day (TDD) model, ALT=K root TDD, we estimated ALT along the ABoVE swaths employing the 2-m air temperature from ERA5. The coefficient (K) calibrated has an R2=0.9783. We also obtained an excellent fit between ALT and K root(TDD/theta) where theta is the soil moisture from ERA5 (R2=0.9719). Output based on shared-social economic pathway (SSP) climate scenarios SSP 1-2.6, SSP 2-4.5, and SSP 5-8.5 from seven global climate models (GCMs), statistically downscaled to 25-km resolution, was used to project the impacts of climate warming on ALT. Assuming ALT=K root TDD, the projections of UKESM1-0-LL GCM resulted in the largest projected ALT, up to about 0.7 m in 2080s under SSP5-8.5. Given that the mean observed ALT of the study sites is about 0.482 m, this implies that ALT will increase by 0.074 to 0.217 m (15% and 45%) in 2080s. This will have substantial impacts on Arctic infrastructure. The projected settlement Iset (cm) of 1 to 7 cm will also impact the infrastructure, especially by differential settlement due to the high spatial variability of ALT and soil moisture, given at local scale the actual thawing will partly depend on thaw sensitivity of the material and potential thaw strain, which could vary widely from location to location.

The distribution and variation of active layer thickness (ALT) are crucial indicators for assessing the stability and environmental conditions of permafrost regions, which significantly impact regional hydrology, ecology, climate change, engineering construction, and disaster risk assessment. Based on the measured ALT data and Stefan equation, this study investigated the spatial distribution characteristics of ALT in the Tuotuo River region and explored the factors influencing its variability. The results showed that the ALT in the Tuotuo River area ranged from 0.15 to 5.18 m, with an average value of 2.65 m. The spatial distribution showed that the ALT was thinner in the southern region, which exhibited strong spatial heterogeneity, while the northeastern region generally had thicker ALT. Additionally, mountain areas tended to have thinner ALT, whereas plains showed thicker ALT. There was a good linear correlation between the simulated and measured ALT values, and the R 2 was up to 80%. The ALT in the Tuotuo River area was mainly controlled by air temperature and surface water thermal conditions. Among all factors, soil water content was identified as the key determinant. Topographic factors influenced ALT distribution and variation mainly through their impact on soil water content.

Understanding the evolution of permafrost extent and active layer thickness (ALT) surrounding Antarctica is critical to global climate change and ecosystem transformations in the polar regions. However, due to the remoteness and harsh environment of Antarctica, most studies lack long-term and a regional perspective on the variations of ALT in Antarctica, resulting in hindering accurate assessment of ALT dynamics. In this study, based on MODIS land surface temperature (LST) and soil climate station data, we used the Stefan model to reconstruct ALT in the ice-free area of the McMurdo Dry Valleys (MDV) in East Antarctica from 2003 to 2022. The modeled ALT was verified against ground observations showing a good correlation (R) of 0.72 (p < 0.001), with an RMSE of 12.66 cm. The results indicate that the ALT exhibits a decreasing trend from coastal to inland, ranging from a maximum of 60 cm near the coastal area to zero in the polar plateau. Furthermore, within the inland valleys, deeper ALT values are mainly distributed in the lower elevation areas, reaching up to 60 cm at the lowest altitudes. During the period from 2003 to 2022, the interannual variability in ALT was notable, especially in coastal areas, with a maximum amplitude close to 30 cm in the years 2012 and 2016. Our study proved that the Stefan model with parameters estimated by MODIS LST and soil climate station data has good potential to reconstruct large-scale ALT in the ice-free area of Antarctica.

This study examines the fragility response of an earthen embankment supported on a liquefiable deposit subjected to pulse and nonpulse ground motions. Fragility curves are developed based on two key parameters, namely, median seismic intensity and overall variability in the analysis. Such curves represent the vulnerability of an earthen embankment under two distinct types of ground motions. Numerical simulations are performed using two-dimensional finite-element analysis under plane strain conditions. The saturated sandy deposits in the foundation are modeled with the UBC3D-PLM constitutive model and calibrated with appropriate parameters. Two damage indexes are introduced: normalized embankment settlement and lateral embankment deformation. Nonlinear incremental dynamic analysis is performed for various ground motions, and fragility parameters are developed for different damage levels. The results show that pulse-type earthquakes cause more serious damage to earthen structures than nonpulse-type earthquakes, increasing the vulnerability. Further, the liquefiable layer thickness in the foundation soil plays a significant role in the vulnerability assessment of the embankment. The foundation liquefiable layer with less thickness may lead to an early onset of damage and lower the seismic demand on the embankment structure at lower damage levels. With an increase in the layer thickness, seismic demand reduces, with the drainage path playing a critical role.

Permafrost is one of the crucial components of the cryosphere, covering about 25% of the global continental area. The active layer thickness (ALT), as the main site for heat and water exchange between permafrost and the external atmosphere, its changes significantly impact the carbon cycle, hydrological processes, ecosystems, and the safety of engineering structures in cold regions. This study constructs a Stefan CatBoost-ET (SCE) model through machine learning and Blending integration, leveraging multi-source remote sensing data, the Stefan equation, and measured ALT data to focus on the ALT in the Qinghai-Tibet Plateau (QTP). Additionally, the SCE model was verified via ten-fold cross-validation (MAE: 20.713 cm, RMSE: 32.680 cm, R2: 0.873, and MAPE: 0.104), and its inversion of QTP's ALT data from 1958 to 2022 revealed 1998 as a key turning point with a slow growth rate of 0.25 cm/a before 1998 and a significantly increased rate of 1.26 cm/a afterward. Finally, based on multiple model input factor analysis methods (SHAP, Pearson correlation, and Random Forest Importance), the study analyzed the ranking of key factors influencing ALT changes. Meanwhile, the importance of Stefan equation results in SCE model is verified. The research results of this paper have positive implications for eco-hydrology in the QTP region, and also provide valuable references for simulating the ALT of permafrost.

Unlike uniform soils, soft clays with sand interlayers in coastal soft clays, can affect their mechanical properties, potentially impacting underground-construction safety and stability. Consolidated undrained cyclic triaxial tests were conducted to study the dynamic properties and deformation behavior of clay, focusing on how the thickness ratio between the sand and clay layers and the cyclic-stress ratio influence the pore pressure, axial strain, shear-modulus ratio, and normalized damping ratio. The results indicate that higher thickness ratios and cyclic-stress ratios lead to a faster decay of the shear-modulus ratio, quicker increases in pore pressure, faster strain accumulation, and fewer cycles to failure. The normalized damping ratio has three different forms: decreasing, decreasing then increasing, and increasing. However, at a cyclic-stress ratio of 0.2 and thickness ratio of 0.25, the samples exhibit better dynamic characteristics. Soft clay with sand layers exhibits characteristics in line with the stability theory. At low thickness and cyclic-stress ratios, purely elastic and elastically stable phases are observed. As the thickness and cyclic-stress ratios increase, it transitions to plastic stability and incremental failure.

Carbon capture and storage plus compressed CO2 energy storage (CCS+CES) is gradually moving from conceptual design to feasible studies. Underground salt caverns are ideal locations for implementing CO2 geological storage. However, earthquakes are among the natural disasters that impact underground salt cavern safety. Based on plastic deformation combined with salt rock self-healing characteristics, this study demonstrates that largescale salt-cavern CO2 storage facilities are repairable under moderate seismic. This study evaluates the impact of salt layers on seismic wave propagation using site transfer functions, while seismic acceleration histories are simulated using the trigonometric series method. Based on the typical operating conditions of CCS+CES, a finite element model is established to analyze the seismic performance of CO2 storage under different salt rock layer thicknesses and internal pressures for magnitude 5 earthquakes and temperatures of 40 degrees C. Then, this study proposes safety evaluation criteria and self-healing criteria for the salt cavern under seismic loading. A comparative analysis is conducted on the damage and self-healing potential of the salt cavern under different conditions. The results show that thicker salt layers result in smaller displacement and stress in the cavern, while higher internal pressure leads to a more significant increase in displacement and stress. According to the failure criteria for salt caverns, the likelihood of failure under moderate seismic loads is low. As a comparison, the seismic response of the salt cavern and the salt cavern with an interlayer under a magnitude 7 earthquake is also studied. The results show that under strong seismic loads, both the salt cavern and the salt cavern with an interlayer are likely to experience failure.

This study aims to optimize geotextile placement depth to enhance subgrade strength and achieve sustainable pavement design. Laboratory tests were conducted to characterize the soil and evaluate the effect of geotextile placement at depths of 3/4D, 1/2D, and 1/4D (where D is the total specimen depth). California bearing ratio (CBR) tests revealed that positioning the geotextile at 0.3D significantly improves subgrade strength, yielding a 78.08% increase in soaked CBR (from 5.84 to 10.4) and a 136.56% improvement in unsoaked conditions (from 3.72 to 8.8). Pavement analysis using IITPAVE software further demonstrated that geotextile placement at 0.3D effectively reduces fatigue and rutting strains, allowing reductions in pavement layer thicknesses-16.67% for bituminous concrete (BC) and dense bituminous macadam (DBM), 38.18% for water bound macadam (WBM), and 25% for granular sub-base (GSB). These optimizations lead to a cost saving of Indian Rupee36,06,610 ($42,430) per kilometer. The findings highlight the practical and economic benefits of placing geotextile at 0.3D depth (150 mm for a 500 mm subgrade), offering improved pavement performance, material savings, and enhanced sustainability. This research benefits pavement engineers, contractors, and transportation agencies by offering a sustainable, cost-efficient design strategy. Additionally, the findings provide a foundation for future research into geosynthetic reinforcement techniques under varying soil conditions, supporting the development of resilient, eco-friendly pavements.

To investigate the influence of the filling thickness and internal water pressure on the stability of a water supply pipeline, a typical pipeline of the Sun Mountain Water Supply Project is selected as the research object. A numerical simulation method is adopted to establish a three-dimensional finite element model integrating a double-line pipeline-artificial fill-foundation to study the influence of different single-layer filling thicknesses and internal water pressures on the mechanical properties of the double-line pipeline. The results of the study show that the relative error between the intrinsic mode of the finite element model of the double-line pipeline and the frequency identified by the dispersion entropy variational mode decomposition (DVMD) method on the measured vibration signals is only 1.55%, which confirms the validity of the finite element model and the accuracy of the results. With increasing soil filling and increasing single-layer filling thickness, the vertical displacement of the double-line pipe gradually increases, with a maximum value of 12.24 mm. With increasing single-layer filling thickness, the rate of increase in the vertical displacement of the double-line pipe increases. With increasing soil filling, the tensile and compressive stresses on the double-line pipe increase gradually, with maximum values of 0.148 MPa and 0.568 MPa, respectively. When the number of cycles is the same, the tensile and compressive stresses of the pipe sheet increase with increasing single-layer filling thickness. When the internal water pressure is 0.6 MPa, the trends of the inner and outer circumferential deformation and tensile and compressive stresses of the left and right lines of the pipes are basically the same. The outer stresses are lower than the inner stresses, among which the tensile stresses are reduced by 25% and 20.1%, and the compressive stresses are reduced by 16% and 18.2%, respectively. Under the joint action of the earth pressure and internal water pressure, the deformation of the double-line pipeline and the compressive stress tended to decrease and then increase, and the tensile stress gradually increased. The research results provide a theoretical reference and basis for similar water supply pipeline projects.

The extent of wildfires in tundra ecosystems has dramatically increased since the turn of the 21st century due to climate change and the resulting amplified Arctic warming. We simultaneously studied the recovery of vegetation, subsurface soil moisture, and active layer thickness (ALT) post-fire in the permafrost-underlain uplands of the Yukon-Kuskokwim Delta in southwestern Alaska to understand the interaction between these factors and their potential implications. We used a space-for-time substitution methodology with 2017 Landsat 8 imagery and synthetic aperture radar products, along with 2016 field data, to analyze tundra recovery trajectories in areas burned from 1953 to 2017. We found that spectral indices describing vegetation greenness and surface albedo in burned areas approached the unburned baseline within a decade post-fire, but ecological succession takes decades. ALT was higher in burned areas compared to unburned areas initially after the fire but negatively correlated with soil moisture. Soil moisture was significantly higher in burned areas than in unburned areas. Water table depth (WTD) was 10 cm shallower in burned areas, consistent with 10 cm of the surface organic layer burned off during fire. Soil moisture and WTD did not recover in the 46 years covered by this study and appear linked to the long recovery time of the organic layer.