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The resource utilisation of mine overburden in subgrade is an essential approach to accelerate environmental governance in mining areas. The present study focuses on investigating the mechanical properties and damage evolution of mine overburden under different environmental factors. The influences of water immersion, freeze–thaw cycles, water and salt migration on the road characteristics of mine overburden with different coarse grain contents (CGCs) were systematically studied and a cumulative damage model of mine overburden was proposed. The durability of mine overburden under the effect of the environmental factors was further compared. The results showed that mine overburden has less frost heave and can be utilised as subgrade filler in seasonally frozen region. With the increase of CGC of mine overburden, the resilient modulus and CBR gradually increase, and the UCS increases first and then decreases. The cumulative damage model of mechanical properties can effectively characterise the failure evolution of mine overburden. The infiltration of sulphate solution turns the mine overburden filler into weak frost heaving soil. The mine overburden with a CGC of 40% – 60% can be selected to improve the environmental adaptation. The wrapping method is recommended to reduce the impact of negative temperature and moisture on mine overburden subgrade. [ABSTRACT FROM AUTHOR]

In this paper, alumina (Al2O3) coatings were prepared via atmospheric plasma spraying. To improve the insulation performance of the as-sprayed coatings, infiltration sealing treatment processes were performed using silicone resin and epoxy resin sealants. The mechanical properties and dielectric strength of the coatings were characterized. For the as-sprayed coating, the average microhardness was 914.94 HV0.2, and the bond strength was 38.07 MPa. The phase composition of the coatings was presented by γ-Al2O3, as the primary phase, and α-Al2O3, as the second phase. The dielectric strengths of the as-sprayed, silicone resin-sealed, and epoxy resin-sealed coatings were 10.27, 15.78, and 17.91 kV/mm, respectively. The results indicate that the porosity of the coatings was reduced, and the dielectric strength was enhanced by the sealing treatment. Sealants filled the pores of the coatings and prevented the accumulation of electric charges, thereby increasing the dielectric strength. The dielectric breakdown of the coatings was due to combined mechanisms of intrinsic, corona discharge, and thermal breakdown. [ABSTRACT FROM AUTHOR]

Significant heterogeneity has been observed among different ecosystem services (ES). Understanding the trade-offs and synergies among ES and delineating ecological functional zones is crucial for formulating regional management policies that improve human well-being and sustainably develop and maintain ecosystems. In this study, we used the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) and Carnegie–Ames–Stanford Approach (CASA) models to evaluate the spatial distribution patterns of nine ES (food supply, raw material supply, water resource supply, water connotation, climate regulation, soil conservation, water purification, habitat quality, and entertainment tourism) in the Qilian Mountains from 2000 to 2018. We also investigated the trade-offs and synergistic relationships among ES through Spearman correlation analysis, identified ES hotspots through exploratory spatial data analysis, and identified ES bundles (ESB) using K-means clustering. Our results revealed that water purification and habitat quality remained relatively stable, while food supply, raw material supply, water resource supply, water conservation, climate regulation, soil conservation, and entertainment tourism increased by 1038.83 Yuan·ha−1, 448.21 Yuan·ha−1, 55.45 mm, 7.80 mm, 0.60 tc·ha−1, 40.01 t·ha−1 and 4.82, respectively. High-value areas for water resource supply were mainly concentrated in the high-altitude mountainous area, whereas high-value areas for soil conservation were found in the western and eastern parts of the study area. The low-value areas of water purification were primarily located in the east, while the remaining six services were highly distributed in the east and were less common in the west. Correlation analysis showed that water resource supply, water conservation, and soil conservation exhibited a synergistic relationship in the Qilian Mountains. Moreover, food supply, raw material supply, climate regulation, habitat quality, and entertainment tourism showed synergistic relationships. However, there were trade-offs between food supply and water purification as well as water resource supply, and habitat quality showed a tradeoff with water resource supply, water conservation, and soil conservation. We identified four ESB. The food supply bundle consisted mainly of farmland ecosystems, while the windbreak and sand fixation and ecological coordination bundles were dominant in the Qilian Mountains. Notably, the area of the water conservation bundle increased significantly. Our comprehensive findings on ES and ESB can provide a theoretical foundation for the formulation of ecological management policies and the sustainable development of ecosystems in the Qilian Mountains. [ABSTRACT FROM AUTHOR]

Ancient cities are excellent spatiotemporal indicators for the study of historical human activities and environmental change. The ancient city of Sanchahe is located at the southern margin of the Mu Us Desert, China. It is an ideal location for studying the complex relationships between historical desertification and human activities. Field observations of the ancient city walls, a well, and a spring, as well as 14C dating, grain size, spatial analysis of archaeological sites, and analyses of historical seismicity, indicated that neotectonics may have contributed to crustal uplift and accelerated fluvial incision of the Wuding River. This rapid incision caused a decline in groundwater levels, which is an important reason for the irreversible environmental degradation around Sanchahe city over the past 800 yr. This study provides new evidence for such environmental degradation and may contribute to a better understanding of historical desertification in the Mu Us Desert. [ABSTRACT FROM AUTHOR]