Search Results (190)

Permafrost degradation, driven by the thawing of ground ice, results in the progressive thinning and eventual loss of the permafrost layer. This process alters hydrological and ecological systems by increasing surface and subsurface water flow, changing vegetation density, and destabilising the ground. The thermal and hydraulic conductivity of permafrost are strongly temperature-dependent, both increasing as the soil warms, thereby accelerating thaw. In addition, thawing permafrost releases large quantities of greenhouse gases, establishing a feedback loop in which global warming both drives and is intensified by permafrost loss. This paper reviews the mechanisms and consequences of permafrost degradation, including reductions in strength and enhanced deformability, which induce landslides and threaten the structural integrity of foundations and critical infrastructure. Permafrost has been investigated and modelled extensively, and various approaches have been devised to address the consequences of thawing permafrost on communities and the built environment. Some techniques focus on keeping the ground frozen via insulation, while others propose local replacement of permafrost with more stable materials. However, given the scale and pace of current changes, systematic remediation appears unfeasible. This calls for increased efforts towards adaptation, informed by interdisciplinary research. Full article

Warm-mix foamed polyurethane modified bitumen (WPB) has been widely promoted due to its significant warm-mix effect and high viscosity. However, it still has problems such as too fast foam dissipation and unstable performance. Waste molecular sieves have an extremely fine pore structure that can absorb moisture. The porous characteristics of waste molecular sieves are used to adsorb water and let it slowly release water in bitumen. If the foam dissipation time can be prolonged and the bitumen expansion speed can be reduced, it will help to stabilize the performance of foamed bitumen. This paper conducts a study on the foaming characteristics and rheological properties of WPB based on waste molecular sieves. First, the bitumen foaming test is used to analyze the foaming characteristics of WPB with waste molecular sieves. Second, the basic properties of warm-mix foamed polymer-modified bitumen, including penetration, softening point, ductility, and viscosity, are investigated. Finally, a dynamic shear rheometer (DSR) is employed to study the high-temperature rutting resistance and high-temperature permanent deformation resistance of warm-mix foamed polymer-modified bitumen. The research results show that the amount of foaming water is the primary factor influencing bitumen foaming. The addition of waste molecular sieves has a significant impact on the intensity and duration of the bitumen foaming reaction. WPB with waste molecular sieves has a greater consistency and better high-temperature performance, but its low-temperature performance is somewhat weakened. The high-temperature deformation resistance of WPB with waste molecular sieves is superior to that of ordinary WPB and is affected by the amount of foaming water. An appropriate amount of foaming water can enable WPB with waste molecular sieves to exhibit excellent high-temperature deformation resistance. Full article

The development of sustainable and energy-efficient asphalt pavements is essential to address the growing demand for climate-neutral transportation infrastructure. This study investigates the structural design and functional performance of low rolling resistance asphalt mixtures utilizing reclaimed asphalt pavement (RAP) and warm mix asphalt (WMA) technologies. Ten mixtures with WMA additive—including asphalt concrete (AC) and stone mastic asphalt (SMA) with and without RAP—were evaluated for volumetric and mechanical performance. Laboratory results show that RAP addition did not compromise compaction nor indirect tensile strength ratio (ITSR), and in some cases improved these properties. SMA and SMA RAP-modified mixtures achieved the highest resistance to rutting (as low as 5.0% rut depth), while AC and SMA mixtures both demonstrated low rolling resistance (coefficients of energy loss 0.00604–0.00636). Resistance to low-temperature cracking was strong for all mixtures, with thermal stress restrained specimen test (TSRST) fracture temperatures ranging from −32.8 °C to −36.0 °C. SMA mixtures generally exhibited superior resistance to fatigue (up to 63 με at 1 million cycles). Overall, three asphalt mixtures with different particle size distribution containing 14% RAP and a WMA additive (SMA 8 S_1 R, SMA 8 S_3 R, and AC 11 VS_2 R) demonstrated the best balance of rolling resistance, durability, and circularity, and are recommended for field trials to support climate-neutral and sustainable road infrastructure. These results encourage broader adoption of circular practices in road infrastructure projects, contributing to lower emissions and life-cycle costs. Full article

The extensive distribution of quaternary sediments and the extraction of underground resources in the Yellow River Delta (YRD) have resulted in significant land subsidence, which accelerates relative sea level (RSL) rise and heightens the risk of coastal inundation. This study uses Sentinel-1A (S1A) imagery and the time-series synthetic aperture radar interferometry (TS-InSAR) method to obtain subsidence information for the YRD. By integrating data from groundwater level monitoring wells, hydrogeological conditions, extensometer monitoring, and drilling wells, we analyze the causes of subsidence and the deformation response to the groundwater level changes in the corresponding aquifers. For the first time in the YRD, this study introduces the high accuracy CoastalDEM v2.1 digital elevation model, combined with absolute sea level (ASL) data, to construct a coastal inundation simulation. This simulation maps the land inundation caused by RSL rise along the YRD in different scenarios. The results indicate significant subsidence bowls in coastal and inland regions, primarily attributed to shallow brine and deep groundwater extraction, respectively. The main subsidence layers in inland towns have been identified, and residual deformation has been observed. Currently, land subsidence has caused a maximum elevation loss of 141 mm/yr in coastal YRD areas, significantly contributing to RSL rise. Seawater inundation simulations suggest that if subsidence continues unabated, 12.84% of the YRD region will be inundated by 2100, with 8.74% of the built-up areas expected to be inundated. Compared to global warming-induced ASL rise, ongoing subsidence is the primary driver of inundation in the YRD coastal areas. Full article

Understanding Holocene high sea levels in the South China Sea (SCS) is critical for understanding climate change and assessing future sea-level rise risks. We provide a comprehensive review of the Holocene highstand in the SCS, focusing on its age, height, and mechanisms. Records reveal a wide range for this highstand: ages span 3480–7500 cal yr BP, while elevations range from −7.40 to 7.53 m relative to the present. Positive elevations dominate (80.5% of records), with the most frequent range being 2–3 m. Regionally averaged formation times suggest a broadly synchronous mid-Holocene high-sea-level event across the SCS, potentially reflecting a global background. The observed variability is attributed to the interplay of multiple factors: global processes like glacial meltwater input and seawater thermal expansion, particularly during the Holocene warm period, and regional neotectonic movements (uplift/subsidence), which are the primary cause of spatial differences in reconstructed elevations. Significant debate persists regarding precise timing, height, and dominant mechanisms due to limitations in data coverage, dating precision, and challenges in quantifying tectonic influences. Future research priorities include obtaining high-resolution data from stable marine sediments, employing diverse dating techniques and modern crustal deformation monitoring, quantifying tectonic impacts, developing regional sea-level models, and enhancing international collaboration to refine understanding and improve predictions of future sea-level rise impacts. Full article

With the expansion of offshore and subsea infrastructure in Arctic and sub-Arctic regions, concerns are rising, driven by climate change and global warming, over the risk of drifting icebergs colliding with these structures in cold waters. Traditional methods for estimating iceberg underwater height and assessing subgouge soil properties, such as costly and time-consuming underwater surveys or centrifuge tests, are still used, but the industry continues to seek faster and more cost-efficient solutions. In this study, the extra tree regression (ETR) algorithm was employed for the first time to simultaneously model iceberg drafts and subgouge soil properties in both sandy and clay seabeds. The ETR approach first predicted the iceberg draft, then simulated subgouge soil reaction forces and deformations. A total of 22 ETR models were developed, incorporating parameters relevant to both iceberg draft estimation and subgouge soil characterization. The best-performing ETR models, along with the most influential input variables, were identified through a combination of sensitivity, error, discrepancy, and uncertainty analyses. The ETR model predicted iceberg draft with a high level of accuracy (R = 0.920, RMSE = 1.081), while the superior model for vertical reaction force in sand achieved an RMSE of 43.95 with 70% of predictions within 16% error. The methodology demonstrated improved prediction capacity over traditional techniques and can serve early-stage iceberg risk management. Full article

The Amazon Basin plays a crucial role in the global hydrological cycle, where seasonal and interannual variations in terrestrial water storage (TWS) are essential for understanding climate–hydrology coupling mechanisms. This study utilizes data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission and its follow-on mission (GRACE-FO, collectively referred to as GRACE) to investigate the spatiotemporal dynamics of hydrological mass changes in the Amazon Basin from 2002 to 2021. Results reveal pronounced spatial heterogeneity in the annual amplitude of TWS, exceeding 65 cm near the Amazon River and decreasing to less than 25 cm in peripheral mountainous regions. This distribution likely reflects the interplay between precipitation and topography. Vertical displacement measurements from the Global Navigation Satellite System (GNSS) show strong correlations with GRACE-derived hydrological load deformation (mean Pearson correlation coefficient = 0.72) and reduce its root mean square (RMS) by 35%. Furthermore, the study demonstrates that existing hydrological models, which neglect groundwater dynamics, underestimate hydrological load deformation. Principal component analysis (PCA) of the Amazon GNSS network demonstrates that the first principal component (PC) of GNSS vertical displacement aligns with abrupt interannual TWS fluctuations identified by GRACE during 2010–2011, 2011–2012, 2013–2014, 2015–2016, and 2020–2021. These fluctuations coincide with extreme precipitation events associated with the El Niño–Southern Oscillation (ENSO), confirming that ENSO modulates basin-scale interannual hydrological variability primarily through precipitation anomalies. This study provides new insights for predicting extreme hydrological events under climate warming and offers a methodological framework applicable to other critical global hydrological regions. Full article

With rising global temperatures and increasing sustainability demands, the need for advanced pavement solutions has never been greater. This study breaks new ground by integrating phase change materials (PCMs), including paraffin-based wax (Rubitherm RT55), hydrated salt (Climator Salt S10), and fatty acid (lauric acid), as binder modifiers within warm mix asphalt (WMA) mixtures. Moving beyond the traditional focus on binder-only modifications, this research utilizes recycled cigarette filters (CFs) as a dual-purpose fiber additive, directly reinforcing the asphalt mixture while simultaneously transforming a major urban waste stream into valuable infrastructure. The performance of the developed WMA mixture has been evaluated in terms of stiffness behavior using an Indirect Tensile Strength Modulus (ITSM) test, permanent deformation using a static creep strain test, and rutting resistance using the Hamburg wheel-track test. Laboratory tests demonstrated that the incorporation of PCMs and recycled CFs into WMA mixtures led to remarkable improvements in stiffness, deformation resistance, and rutting performance. Modified mixes consistently outperformed the control, achieving up to 15% higher stiffness after 7 days of curing, 36% lower creep strain after 4000 s, and 64% reduction in rut depth at 20,000 passes. Cost–benefit analysis and service life prediction show that, despite costing USD 0.71 more per square meter with 5 cm thickness, the modified WMA mixture delivers much greater durability and rutting resistance, extending service life to 19–29 years compared to 10–15 years for the control. This highlights the value of these modifications for durable, sustainable pavements. Full article

Frictional conditions at the workpiece–die interface are critical in metal forming, as significant plastic deformation generates heat that affects lubricant performance. Understanding lubricant behavior, especially its influence on friction under elevated temperatures, is essential for optimizing forming processes and meeting ecological demands. While the conventional ring compression test evaluates friction through inner diameter changes, it becomes unreliable when friction is transient. In this study, a warm ring compression test incorporating an in situ measurement system is proposed to evaluate the transient frictional behavior of lubricants under temperature rise due to plastic deformation. Results show that at T = 50 °C and 150 °C, the friction coefficient increases notably with the compression ratio, whereas at T = 100 °C, it remains relatively stable. This stability is likely due to the optimal performance of the chlorinated base lubricant at 100 °C, where boundary lubrication is most effective. At T = 50 °C, the additive activation is insufficient, and at T = 150 °C, thermal degradation may reduce its effectiveness. Finite element simulations using the transient friction coefficient reproduce the deformed ring cross-section with high accuracy, while those using constant friction values show less agreement. Full article

The pressing issue of global warming has prompted industries to seek sustainable and renewable materials that can reduce the use of petroleum-based products. Natural fibers, as bio-based and environmentally friendly materials, offer a promising solution. In this study, ramie fiber, which is one of the strongest natural fibers, is used as reinforcement, and the mechanical properties of natural rubber composites are evaluated. The composites were fabricated using a vulcanizing technique at 150 °C, and the fibers were cut into different lengths (5 mm, 10 m, and 15 mm) and weights (15 g, 30 g, and 60 g). Mechanical performance tests, including tensile and tear strength and hardness, were conducted. The results showed that as fiber concentration increased, so did the curing time. Moreover, the composites with higher fiber concentration had higher strength. The composite with a 10 mm fiber length and 60 g weight showed the highest tensile strength (10.35 MPa). Maximum tear strength (52.51 kN/m) was achieved with 5 mm fiber length and 60 g weight. Hardness values reached up to 88 Shore A (10 mm fiber length and 60 g weight), indicating excellent wear resistance. The specimen with the highest tensile strength was subjected to scanning electron microscope analysis. The SEM analysis revealed that the composite had a ductile type of fracture with appreciable plastic deformation, confirming good fiber–matrix interaction. These findings underscore the potential of ramie fiber–reinforced natural rubber composites as sustainable, high-performance alternatives to petroleum-based materials in structural and vibration-damping applications. Full article

In this study, we have explored the thermomechanical processing on 0.1C3Mn steel to produce an ultrafine-grained (UFG) dual-phase (DP) microstructure. The composition was designed to allow a decrease in temperature for the warm deformation of austenite. It was found that the warm deformation of austenite induced a dramatic ferrite transformation, in contrast to the absence of the formation of ferrite in the well-annealed state. Compression by 60% at 650 °C resulted in the generation of a UFG-DP microstructure with a ferrite grain size of 1.4 μm and a ferrite volume fraction of 62%. The UFG-DP 0.1C3Mn steel presents a good combination of strength, ductility and fracture resistance, and the fracture strain of the UFG-DP is higher than the as-quenched low-carbon martensite. The high fracture strain of the UFG-DP could be attributed to delayed void nucleation and constrained void growth, as revealed by the quantitative X-ray tomography. Full article

Variations in the warm formability of AA7075 sheets are primarily attributed to differences in precipitate morphology resulting from distinct thermal histories. To better understand this relationship, this study systematically investigates the influence of precipitate characteristics—quantified by the product of precipitate volume fraction and average radius—on forming limits across various thermal routes in warm forming processes. A modified Cockcroft–Latham ductile fracture model incorporating this microstructural parameter was developed, calibrated against experimental data from warm isothermal Nakajima tests, and implemented within a finite element framework. The proposed model enables the accurate prediction of forming limit curves with minimal experimental effort, thereby significantly reducing the reliance on extensive mechanical testing. Building upon the validated FE model, a practical methodology for rapid R-value estimation under warm forming conditions was established, involving the design of specimen geometries optimised for isothermal Nakajima testing. This approach achieved R-value predictions within 5% deviation from conventional uniaxial tensile test results. Furthermore, experimental results indicated that AA7075 sheets exhibited nearly isotropic deformation behaviour under retrogression warm forming conditions. Overall, the methodology proposed in this study bridges the gap between formability prediction and process simulation, offering a robust and scalable framework for the industrial optimisation of warm forming processes for high-strength aluminium alloys. Full article

This study assesses the risks of glacial lake outburst floods (GLOFs) from moraine sediment dams around Gurudongmar Lake in the Northern Sikkim Himalayas at an elevation of 17,800 feet. It focuses on three moraine sediment dams, analysing the implications of slope failure on the upstream side and the downstream stability under steady seepage conditions, as well as the risks posed by permafrost thawing. Using a comprehensive methodology that includes geotechnical evaluations, remote sensing, and digital elevation models (DEMs), the research employs finite element analysis via PLAXIS2D for the stability assessment. The main findings indicate a stratification of sediment types: the upper layers are loose silty sand, while the lower layers are dense silty sand, with significant variations in shear strength, permeability, and other geotechnical properties. Observations of solifluctions suggest that current permafrost conditions enhance the dams’ stability and reduce seepage. However, temperature trends show a warming climate, with the average days below 0 °C decreasing from 314 (2004–2013) to 305 (2014–2023), indicating potential permafrost thawing. This thawing could increase seepage and destabilise the dams, raising the risk of GLOFs. Numerical simulations reveal that scenarios involving water level rises of 5 and 10 m could lead to significant deformation and reduced safety factors on both the upstream lateral dams and downstream front dams. The study emphasises the urgent need for ongoing monitoring and risk assessment to address the potential hazards associated with GLOFs. Full article

The Arctic is the fastest-warming region on Earth, exhibiting a pronounced “amplifying effect”, which has triggered widespread permafrost thaw and increased the risk of surface deformation. In the Arctic coastal lowlands, permafrost is also affected by shoreline retreat. The impact of these dual stressors on surface deformation processes in the Arctic coastal lowlands remains poorly understood, particularly in terms of how permafrost thaw and shoreline retreat interact to influence surface stability. To address this gap, we employed PS-InSAR technology to monitor surface deformation from 2017 to 2021 at Tiksi Airport, the northernmost airport on the Siberian mainland, situated adjacent to the Laptev Sea. The results show that Tiksi Airport experiences localized significant surface subsidence, with deformation velocity ranging from −42 to 39 mm/yr. The near-coastal area of Tiksi Airport is strongly influenced by the ocean. Specifically, for extreme subsidence deformation (around –40 mm/yr), the surface subsidence velocity increases by 0.2 mm/yr for every 100 m closer to the coastline. Analysis of these deformation characteristics suggests that the primary causes of subsidence are land surface temperature (LST) warming and erosion by the Laptev Sea, which together lead to increased permafrost thaw. By revealing the combined effects of climate warming and coastal erosion on permafrost stability, this study contributes to enhancing the understanding of infrastructure safety and quality of life for residents in Arctic coastal subsidence areas. Full article

Due to the need for weight reduction in the automobile structure, effective and accurate forming is demanded to take advantage of ultrahigh-strength steels. Research on the deep-drawing formability of Usibor^®2000 has an important impact on the application of lightweight automotive bodies. The microstructure and formability of Usibor^®2000 sheets at different temperatures were investigated by the Swift test. The positive effects of increasing the temperature on improving the forming limit and forming quality of Usibor^®2000 were demonstrated by LDR results, thickness, and hardness measurement. The microstructure evolution of Usibor^®2000 steel plates under warm forming and hot forming conditions was discussed in terms of microstructure characterization and precipitate morphology. The phase composition of the sample deformed at 860 °C is analyzed by two-step etching metallographic analysis and numerical simulation, which provides a reference for the application of Usibor^®2000 ultrahigh-strength steel in automotive lightweight. Full article