In high-mountain contexts, rainfall can trigger various flow-like mass movements, from debris flows to hyperconcentrated flows and flash floods. Despite similar runout and velocity, propagation mechanisms are different. In such complex phenomena, also the existing protection structures play a fundamental role. In this paper, a multi-phase mathematical framework is adopted to simulate the propagation of a mixture of soil and water along a 3D terrain model. The mass and momentum conservation equations are solved including the rheological behavior models for the materials involved: frictional for soil, Newtonian for water. Some selected scenarios are discussed for a site-specific case study in Northern Italy. The controversial role played by two storage basins located at the toe of the gully is explored numerically and compared to the field evidence. The novelty of the paper is to show how the water temporarily impounded in the basins enhanced the mobility of an incoming debris flow, which turned into an hyperconcentrated flow and went out of the protections structure.

Numerous endorheic lakes in the Qinghai-Tibet Plateau (QTP) have shown a dramatic increase in total area since 1996. These expanding lakes are mainly located in the interior regions of the QTP, where permafrost is widely distributed. Despite significant permafrost degradation due to global warming, the impact of permafrost thawing on lake evolution in QTP has been underexplored. This study investigated the permafrost degradation and its correlation with lake area increase by selecting four lake basins (Selin Co, Nam Co, Zhari Namco, and Dangqiong Co) in QTP for analysis. Fluid-heat-ice coupled numerical models were conducted on the aquifer cross-sections in these four lake basins, to simulate permafrost thawing driven by rising surface temperatures, and calculate the subsequent changes in groundwater discharge into the lakes. The contribution of these changes to lake storage, which is proportional to lake area, was investigated. Numerical simulation indicates that from 1982 to 2011, permafrost degradation remained consistent across the four basins. During this period, the active layer thickness first increased, then decreased, and partially transformed into talik, with depths reaching up to 25 m. By 2011, groundwater discharge had significantly risen, exceeding 2.9 times the initial discharge in 1988 across all basins. This increased discharge now constitutes up to 17.67 % of the total lake water inflow (Selin Co). The dynamic lake water budget further suggests that groundwater contributed significantly to lake area expansion, particularly since 2000. These findings highlight the importance of considering permafrost thawing as a crucial factor in understanding the dynamics of lake systems in the QTP in the context of climate change.

To ensure the mud discharge performance of the atmospheric cutterhead and reduce the risk of clogging, it is necessary to consider the distribution of soil in the cutterhead opening under different tunneling parameters. Taking the Haizhuwan tunnel project as an example, the rheological properties of soil and slurry samples were collected and analyzed. The full-scale mud discharge model of cutterhead was established for the first time by using the Euler multiphase flow model. By examining the pressure value of the monitoring point of the excavation chamber, the simulation parameters agree with the field-measured data. The simulation results show that the soil content in the center area and the edge area of the cutterhead is more than 60% and 15% respectively, which is much higher than that in other areas. The mathematical model of soil content and tunneling parameters was established, and the measures to reduce the soil content were explored. By comprehensively analyzing the variation law of soil content in the central and edge areas, it is beneficial to improve the mud discharge performance of the cutterhead by reducing the penetration rate and increasing the cutterhead rotation speed and grouting rate.

With the rapid growth of shield-discharged soil (SDS), there is an increasing demand for effective recycling and transformation methods. This study aims to develop an alkali-activated controlled low-strength material (CLSM) by utilizing ground granulated blast furnace slag (GGBFS) and fly ash (FA) as precursors, SDS as fine aggregate, and sodium hydroxide (NaOH) solution as an activator. The Box-Behnken design (BBD) within the response surface methodology (RSM) framework was employed, considering liquid-to-solid ratio, alkali equivalent, aggregate-to-binder ratio, and foam agent content (FC) in SDS as key factors. Regression models were constructed to analyze the effects of these factors on flowability, bleeding rate, setting time, compressive strength, elastic modulus, and water absorption. The results confirmed the effectiveness of RSM in determining optimal conditions for material performance. In addition, microscopic analyses were conducted to explore hydration products, microstructural characteristics, and pore distribution. The findings revealed that the fresh density of the CLSM ranged from 1460 to 1740 kg/m(3), classifying it as a low-density material. The 28-day compressive strength varied from 1.837 to 7.884 MPa, while the setting time ranged between 1.2 and 5.6 hours. These properties comply with the ACI 229 standard and are suitable for practical applications. Interestingly, when the aggregate-to-binder (A/B) ratio was between 0.2 and 0.4, increasing the ratio did not lead to a consistent reduction in mechanical properties. Instead, the properties initially decreased and then improved. Moreover, an increase in foam agent content (FC) extended the setting time and reduced mechanical strength. The correlation coefficients of all models exceeded 0.98, with a coefficient of variation below 10 % and a signal-to-noise ratio greater than 4, demonstrating strong reliability and accuracy of the models. Additionally, the average relative error between predicted and experimental values in six scenarios was under 6 %, validating the feasibility of optimizing the design of alkali-activated CLSM using RSM. The formation of Ca(OH)(2) crystals facilitates early strength development, resulting in final cementitious materials reticular, fibrous C-S-H, C-A-H, and other gel-like hydration products. Calcium promotes the formation of gels such as C-S-H, shortening the setting time and enhancing microstructural density. This study provides valuable insights for optimizing the design of alkali-activated CLSM containing SDS, thereby expanding methods for utilizing construction and demolition waste.

Seasonally frozen ground (SFG) is a significant component of the cryosphere, and its extent is gradually increasing due to climate change. The hydrological influence of SFG is complex and varies under different climatic and physiographic conditions. The summer rainfall dominant climate pattern in Qinghai Lake Basin (QLB) leads to a significantly different seasonal freeze-thaw process and groundwater flow compared to regions with winter snowfall dominated precipitation. The seasonal hydrological processes in QLB are not fully understood due to the lack of soil temperature and groundwater observation data. A coupled surface and subsurface thermal hydrology model was applied to simulate the freeze-thaw process of SFG and groundwater flow in the QLB. The results indicate that SFG begins to freeze in early November, reaches a maximum freezing depth of approximately 2 meters in late March, and thaws completely by June. This freeze-thaw process is primarily governed by the daily air temperature variations. During the early rainy season from April to June, the remaining SFG in deep soil hinders the majority of rainwater infiltration, resulting in a two-month delay in the peak of groundwater discharge compared to scenario with no SFG present. Colder conditions intensify this effect, delaying peak discharge by 3 months, whereas warmer conditions reduce the lag to 1 month. The ice saturation distribution along the hillslope is affected by topography, with a 10 cm deeper ice saturation distribution and 3 days delay of groundwater discharge in the steep case compared to the flat case. These findings highlight the importance of the freeze-thaw process of SFG on hydrological processes in regions dominated by summer rainfall, providing valuable insights into the hydro-ecological response. Enhanced understanding of these dynamics may improve water resource management strategies and support future research into climate-hydrology interactions in SFG-dominated landscapes.

The development of a nonconventional nitrogen fertilizer, which can be fixed in agricultural fields using decentralized renewable energy sources, presents a feasible solution for sustainable on-site nitrogen fixation and fertilization. This study focuses on plasma-generated dinitrogen pentoxide (N2O5) as a prospective mediator for the on-site nitrogen fertilization, allowing nitrogen fertilization directly into culture media. Basal dinitrogen pentoxide fertilization demonstrated almost 100% dinitrogen pentoxide dissolution efficiency as nitrate in a culture medium and nitrogen fertilization effect on plant growth without explicit symptoms of damage. Top-dressing of dinitrogen pentoxide was also an efficient method for transferring nitrogen into the soil as nitrate, which improved plant growth and suppressed nitrogen deficiency symptoms, while overdose caused adverse effects. Plants can be grown with dinitrogen pentoxide (N2O5), acting as a nitrogen fertilizer remotely synthesized from air by on-site plasma nitrogen fixation. Both basal N2O5 fertilization and top-dressing of N2O5 gas over soil significantly improved plant growth owing to high dissolution efficiency into liquid and soil. image

To address data scarcity on long-term glacial discharge and inadequacies in simulating and predicting hydrological processes in the Tien Shan, this study analysed the observed discharge at multiple timescales over 1980s-2017 and projected changes within a representative glacierized high-mountain region: eastern Tien Shan, Central Asia. Hydrological processes were simulated to predict changes under four future scenarios (SSP1, SSP2, SSP3, and SSP5) using a classical hydrological model coupled with a glacier dynamics module. Discharge rates at annual, monthly (June, July, August) and daily timescales were obtained from two hydrological gauges: Urumqi Glacier No.1 hydrological station (UGH) and Zongkong station (ZK). Overall, annual and summer discharge increased significantly ( p < 0.05) at both stations over the study period. Their intra-annual variations mainly resulted from differences in their recharge mechanisms. The simulations show that a tipping point in annual discharge at UGH may occur between 2018 and 2024 under the four SSPs scenarios. Glacial discharge is predicted to cease earlier at ZK than at UGH. This relates to glacier type and size, suggesting basins with heavily developed small glaciers will reach peak discharge sooner, resulting in an earlier freshwater supply challenge. These findings serve as a reference for research into glacial runoff in Central Asia and provide a decision-making basis for planning local water-resource projects.

Climate change has regulated cryosphere-fed rivers and altered interannual and seasonal sediment dynamics, with significant implications for terrestrial material cycles and downstream aquatic ecosystems. However, there has been a notable scarcity of research focusing on the patterns of water-sediment transport within these permafrost zones. Integrating 6 years (2017-2022) of in-situ observational data from FengHuoShan basin with the partial least squares-structural equation modelling (PLS-SEM) method, we analyse the driving factors, characteristics and seasonal patterns of the water-sediment transport process. We observed a gradual increase in both suspended sediment flux (SSF, Mt/yr) and runoff (Q, km(3)/yr) within the basin, with annual growth rates of 1.34%/yr and 0.75%/yr, respectively. It is worth noting that these growth rates exhibit seasonal variations, with the highest values observed in spring (SSF: 1.76%/yr, Q: 1.71%/yr). This indicates that the response to climate change is more pronounced in spring compared with summer and autumn. Through mathematical statistics and the PLS-SEM model, we found that temperature plays a predominant role in the dynamics of water-sediment in both spring and autumn, whereas rainfall exerts a more significant impact during the summer. Most suspended sediment concentration (SSC, kg/m(3)) peak events throughout the year are primarily driven by rainfall. Affected by the freeze-thaw cycle of permafrost, SSC and discharge (Q, m(3)/s) exhibit distinct seasonality. SSC and Q demonstrate a clockwise trend; both Q and SSC begin to increase from May and peak in August before declining. The insights gleaned from this study hold significant implications for water resource management and soil conservation strategies in the region, particularly in the face of ongoing climatic changes characterized by warming and increased humidity.

Extreme climate events such as storms and severe droughts are becoming more frequent under the warming climate. In the tropics, excess rainfall carried by hurricanes causes massive flooding and threatens ecosystems and human society. We assessed recent major floodings on the tropical island of Puerto Rico after Hurricane Maria in 2017 and Hurricane Fiona in 2022, both of which cost billions of dollars damages to the island. We analyzed the Sentinel-1 synthetic aperture radar (SAR) images right after the hurricanes and detected surface inundation extent by applying a random forest classifier. We further explored hurricane rainfall patterns, flow accumulation, and other possible drivers of surface inundation at watershed scale and discussed the limitations. An independent validation dataset on flooding derived from high-resolution aerial images indicated a high classification accuracy with a Kappa statistic of 0.83. The total detected surface inundation amounted to 10,307 ha after Hurricane Maria and 7949 ha after Hurricane Fiona for areas with SAR images available. The inundation patterns are differentiated by the hurricane paths and associated rainfall patterns. We found that flow accumulation estimated from the interpolated Fiona rainfall highly correlated with the ground-observed stream discharges, with a Pearson's correlation coefficient of 0.98. The detected inundation extent was found to depend strongly on hurricane rainfall and topography in lowlands within watersheds. Normal climate, which connects to mean soil moisture, also contributed to the differentiated flooding extent among watersheds. The higher the accumulated Fiona rain and the lower the mean elevation in the flat lowlands, the larger the detected surface flooding extent at the watershed scale. Additionally, the drier the climate, which might indicate drier soils, the smaller the surface flooding areas. The approach used in this study is limited by the penetration capability of C-band SAR; further application of L-band images would expand the detection to flooding under dense vegetation. Detecting flooding by applying machine learning techniques to SAR satellite images provides an effective, efficient, and reliable approach to flood assessment in coastal regions on a large scale, hence helping to guide emergency responses and policy making and to mitigate flooding disasters.

Cylindrical steel silos with flat bottoms are widely used in agriculture and industry for storing granular materials. While research has advanced our understanding of pressure on silo walls, accurate prediction, especially during the dynamic filling and discharge phases, remains a challenge. This study presents a finite element (FE) analysis of pressure distribution in a model cylindrical steel silo with a flat bottom, investigating the influence of the height-to-diameter (H/D) ratio. The numerical results were validated against experimental data from a pilot-scale test facility storing corn. Material properties were determined through laboratory experiments, with mechanical properties obtained from literature. An arbitrary Lagrangian formulation was employed for the FE calculations. The FE results showed good agreement with experimental data for static pressure distribution on the silo wall across all H/D ratios analyzed. While the patterns of dynamic pressure curves were similar, the FE-predicted magnitudes were lower than those observed experimentally. Notably, the simulations captured significant pressure fluctuations during silo discharge.