Huanan Liu

Frost heave of transmission tower foundations in seasonally frozen regions endangers cold-region power infrastructure and grid security. This study establishes a coupled model to simulate foundation freeze-thaw and frost heave processes, validated via laboratory tests. The results demonstrate that the high thermal conductivity of the tower foundation alters the temperature field distribution, inducing preferential development of the freezing front along the foundation interface. During freezing, temperature gradients drive unfrozen water migration toward the freezing front, resulting in locally high-saturation zones in shallow soil after freeze-thaw. After freeze–thaw, plastic deformation of the soil and compression and rearrangement of soil particles degrade the uplift capacity of the tower foundation and prevent full recovery of its initial position, thereby producing residual displacement. Increases in the number of freeze–thaw cycles and initial water content both intensify the cumulative frost jacking effect on the tower foundation; moreover, soil with higher water content is more susceptible to consolidation settlement after thawing. The experimental data confirmed the reliability of the coupling model. These findings offer a theoretical foundation and numerical analysis methods for the long-term sustainable operation and maintenance of infrastructure in seasonally frozen regions.

Improving water retention, erosion resistance and nutrients in desert areas is essential for ecological sustainability. This study evaluated the effects of biochar, polyethylene oxide (PEO), and seaweed fertilizer on the properties of desert sandy soil, focusing on water retention, erosion resistance, and soil nutrients. The sandy soil used in the study was taken from the Tengger Desert in Gansu, China, and an orthogonal experimental design was used to select three different proportions of biochar, PEO, and seaweed fertilizer. Compared with the control, applying of these three substances decreased bulk density by 5.8–9.6%, increased porosity by 8.3–14%, and increased water-holding capacity by 2.2–6.7%. The erosion rate decreased by more than 99%, and water-stable aggregates increased by 9.7–37.4%. Soil nutrients showed varying degrees of increase, and seed germination increased by 26.7%. The results of the principal component analysis showed that B6P0.6S2 had the best overall improvement effect. Therefore, a ratio of 6% biochar, 0.6% PEO, and 2% seaweed fertilizer is recommended to improve the properties of sandy desert soils. Overall, biochar, PEO, and seaweed fertilizer can improve the physical properties of desert sandy soil, enhance soil nutrients, and create a stable and suitable environment for plant growth.

In seasonally frozen soil areas, high-steep rocky slopes resulting from open-pit mining and slope cutting during road construction undergo slow natural restoration, making ecological restoration generally challenging. In order to improve the problems of external soil attachment and long-term vegetation growth in the ecological restoration of high-steep rocky slopes in seasonally frozen areas, this study conducted a series of experiments through the combined application of polyacrylamide (PAM) and carboxymethyl cellulose (CMC) to assess the effects of soil amendments on soil shear strength, water stability, freeze–thaw resistance, erosion resistance, and vegetation growth. This study showed that the addition of PAM-CMC significantly increased the shear resistance and cohesion of the soil, as well as improving the water stability, freeze–thaw resistance, and erosion resistance, but the internal friction angle of the soil was not significantly increased after reaching a certain content. Moderate amounts of PAM-CMC can extend the survival of vegetation, but overuse may cause soil hardening and inhibit vegetation growth by limiting air permeability. It was observed by a scanning electron microscope (SEM) that the gel membrane formed by PAM-CMC helped to “bridge” and bind the soil particles. After discussion and analysis, the optimum application rate of PAM-CMC was 3%, which not only improved the soil structure but also ensured the growth of vegetation in the later stage under the optimum application rate. Field application studies have shown that 3% PAM-CMC-amended soil stably attaches to high-steep rocky slopes, with stable vegetation growth, and continues to grow after five months of freeze–thaw action, with no need for manual maintenance after one year.

Collapses are one of the most common geological disasters in mountainous areas, which easily damage buildings and infrastructures and bring huge property losses to people’s production and life. This paper uses Huinan County as the study area, and with the help of a geographic information system (GIS) based on the formation principle of natural disaster risk, the information content method (ICM), the analytical hierarchy process (AHP), and the analytical hierarchy process–information content method (AHP-ICM) model are applied to hazard mapping, and the analytical hierarchy process-entropy weight method (AHP-EWM) model is applied to exposure, vulnerability and emergency responses, and recovery capability mapping. A risk mapping model for collapse disasters was also constructed using these four elements. Firstly, an inventory map of 52 landslides was compiled using remote sensing interpretation, field verification, and comprehensive previous survey data. Then, the study area mapping units were delineated using the curvature watershed method in the slope unit, and 21 indicators were used to draw the collapse disaster risk zoning map by considering the four elements of geological disaster risk. The prediction accuracy of the three hazard mapping models was verified using the receiver operating characteristic (ROC) curve, and the area under the curve (AUC) results of the AHP, ICM, and AHP-ICM models were 80%, 85.7%, and 87.4%, respectively. After a comprehensive comparison, the AHP-ICM model is the best of the three models in terms of collapse hazard mapping, and it was applied to collapse risk mapping with the AHP-EWM model to produce a reasonable and reliable collapse risk zoning map, which provides a basis for collapse management and decision making.

Urban seismic hazards are natural disasters caused by earthquakes in urban areas, which may lead to serious casualties, the collapse of buildings, infrastructure damage, and other impacts, require huge social resources for recovery and reconstruction, and even affect the security stability and sustainable development of the area. This paper adopts the research idea of “Risk = Hazard × Exposure × Vulnerability ÷ Emergency response and recovery capability” and constructs an evaluation system containing 24 representative indicators on this basis. The CF-logistic regression model is applied in the study to calculate the seismic hazard, while the combined weight-TOPSIS model is used to assess the vulnerability of urban hazard-bearing body. Lastly, the study conducts multi-criteria seismic risk evaluation using the GIS platform. The results show that the overall seismic risk in Songyuan is moderate, with 18.66% of the medium-risk area, 37.68% of the very low risk area, 33.96% of the low-risk area, 8.47% of the high-risk area, and 1.23% of the very high-risk area. The significance of this study is to provide a scientific basis for formulating corresponding disaster prevention and mitigation measures and emergency plans, improving urban disaster prevention and emergency response capabilities, reducing urban earthquake disaster losses, and helping to achieve safe and stable urban development.

The frequent occurrence of urban flooding in recent years has resulted in significant damage to ground-level infrastructure and poses a substantial threat to the metro system. As the central city’s core transportation network for public transit, this threat can have unpredictable consequences on travel convenience and public safety. Therefore, assessing the risk of urban flooding in the metro system is of utmost importance. This study is the first of its kind to employ comprehensive natural disaster risk assessment theory, establishing an assessment database with 22 indicators. We propose a GIS-based method combined with the analytical hierarchy process (AHP) and an improved entropy weight method to comprehensively evaluate the urban flood risk in Changchun City’s metro systems in China. This study includes a total of nine metro lines, including those that are currently operational as well as those that are in the planning and construction phases, situated in six urban areas of Changchun City. In this study, we utilize the regional risk level within the 500 m buffer zone of the metro lines to represent the flood risk of the metro system. The proposed method assesses the flood risk of Changchun’s rail transit system. The results reveal that over 30% of Changchun’s metro lines are located in high-risk flood areas, mainly concentrated in the densely populated and economically prosperous western part of the central city. To validate the risk assessment, we vectorized the inundation points and overlaid them with the regional flood risk assessment results, achieving a model accuracy of over 90%. As no large-scale flood events have occurred in the Changchun rail transit system, we employed receiver operating characteristic (ROC) curves to verify the accuracy of the flood risk assessment model, resulting in an accuracy rate of 91%. These findings indicate that the present study is highly reliable and can provide decision makers with a scientific basis for mitigating future flood disasters.

Clean groundwater resources are vital to human health. To evaluate groundwater quality in the Songnen Plain (Jilin), a field investigation sampling test, multivariate statistical analysis, and spatial analysis were conducted based on a geographic information system. The main substances exceeding the standard were screened out, and the main controlling factors affecting groundwater quality were discussed. The research result showed that nine components exceeded groundwater standards by approximately 10%: Al, total hardness (TH), total dissolved solids (TDS), Mn, As, NO₃⁻, Fe, F⁻, and BaP. The over-standard of TDS and TH in groundwater are mainly distributed in the geological environment conditions and unreasonable exploitation and utilization of groundwater in this area. The results of the multi-index evaluation showed that the most important factors affecting groundwater quality were general chemical indices, followed by inorganic toxicology and heavy metals. Controlling the overexploitation of water resources, controlling agricultural activities and sewage discharge, and implementing water conservation systems are the main pathways to improve water quality in the study area. The research results can provide a reference for groundwater pollution control and water resource protection in the Songnen Plain (Jilin).