In cold regions, heat-insulating layers play a crucial role in frost prevention in tunnels. This paper presents a numerical study on the anti-freezing behavior of a cold region tunnel (the Dege tunnel) with heat-insulating layers. A numerical model based on the temperature field coupling theory is firstly proposed and validated using field test data of the Dege tunnel. Subsequently, a comprehensive parametric study is carried out to investigate the influences of heat-insulating layers on the temperature characteristics of airflows inside the tunnel, the surrounding rock, and the tunnel lining. Furthermore, a numerical investigation based on the proposed numerical model is carried out to propose reasonable design parameters of heat-insulating layers for different velocities of mechanical ventilation, and different heat-insulating materials for cold region tunnels. The numerical results show that using the heat-insulating layer can effectively reduce the heat transfer between the surrounding rock and the airflow inside the tunnel. It is also found that the design parameters for the heat-insulating layer are greatly affected by the tunnel ventilation conditions and heat-insulating materials. Full article

The Baiyanghe uranium deposit is a currently important medium-sized deposit in the Xuemisitan area, Xinjiang. The hydrothermal alteration in this deposit is closely related to the uranium mineralization of the deposit. In this study, hyperspectral data are collected from drill cores in the Baiyanghe uranium deposit using a FieldSpec4 visible-shortwave infrared spectrometer to study the hydrothermal alteration. The results reveal that the altered mineral assemblages have obvious zonation characteristics: (1) the upper section comprises long-wavelength illite and minor hematite and montmorillonite; (2) the middle section contains three types of illite (long-, medium- and short-wavelength illite) and hematite; and (3) the lower section includes short-wavelength illite, chlorite and carbonate. Additionally, the variety in the characteristic absorption-peak wavelength of illite at 2200 nm gradually shifts to shorter wavelength and ranges between 2195 nm and 2220 nm with increasing depth, while the SWIR-IC (short-wavelength infrared illite crystallinity, a dimensionless quantity) of the drill holes gradually increases from 0.2 to 2.1. These patterns reflect the hydrothermal fluid activity in the deposit, which features relatively high-temperature, high-pressure hydrothermal fluid in the deeper section and low-temperature, low-pressure hydrothermal fluid in the shallower section. Additionally, the uranium mineralization is located near the fracture zone, which represents the center of hydrothermal fluid activity or mineralization. This area has abundant alteration minerals, and the minerals illite (short- and medium-wavelength), hematite and fluorite can be used as uranium-prospecting indicators for uranium exploration in the deeper sections of the Baiyanghe uranium deposit. Full article

Double-arched tunnel is a special and complex underground structure which needs to be monitored carefully during construction. Taking the Gangkou tunnel as the engineering background, this paper presents a case study of field monitoring of a representative double-arched tunnel. Typical cross sections were chosen in each class of surrounding rock masses in the tunnel area and different types of sensors were embedded in designed locations, and the deformations and forces of both surrounding rocks and lining structures were monitored systematically. The dynamic evolution as well as the spatial distribution characteristics of the monitoring data including the internal displacements of surrounding rocks and the contact pressures between surrounding rocks and primary linings, the axial forces in rock bolts and the internal forces in both steel arches and secondary linings were analyzed. The monitoring and analysis results show that the deformations and forces of both surrounding rocks and lining structures are directly related to the construction procedures, geological conditions and locations in the double-arched tunnel. According to the results, some reasonable suggestions were provided for the improvement of the tunnel construction. This study will provide useful reference and guidance for the design, construction and monitoring of similar engineering projects in future. Full article

The rheological properties of drilling fluid have important effects during drilling in natural gas hydrate at low temperatures. The present study was performed using theoretical analysis. Experiments and micro-analyses were carried out to determine the rheological properties with temperature response characteristics and the mechanism involved in solid-free polymer drilling fluid (SFPDF) at low temperatures when drilling in permafrost with natural gas hydrates (NGH). The curves of shear stress with the shear rates of three kinds of polymer drilling fluids, Semen Lepidii natural vegetable gum, polyacrylamide, and xanthan gum, were drawn. Then, statistical and related analyses of test data were performed using Matlab ver. 8.0. Through regression analysis, the Herschel–Bulkley model was used to characterize the rheological characteristics of SFPDF. On this basis, the laws regarding the rheological properties of the three kinds of SFPDF under changing temperatures were analyzed and rheological properties with temperature response state equations were established. Next, the findings of previous studies on rheological properties with temperature response characteristics of the SFPDF were reviewed. Finally, the rheological properties with temperature response mechanisms were assessed using scanning electron microscopy and infrared spectrum analysis. Full article

To investigate the dynamics and relative drivers of cellulose degradation during litter decomposition, a field experiment was conducted in three individual ecosystems (i.e., forest floor, stream, and riparian zone) of an alpine forest meta-ecosystem on the eastern Tibetan Plateau. Four litter species (i.e., willow: Salix paraplesia, azalea: Rhododendron lapponicum, cypress: Sabina saltuaria, and larch: Larix mastersiana) that had varying initial litter chemical traits were placed separately in litterbags and then incubated on the soil surface of forest floor plots or in the water of the stream and riparian zone plots. Litterbags were retrieved five times each year during the two-year experiment, with nine replicates each time for each treatment. The results suggested that foliar litter lost 32.2%–89.2% of the initial dry mass depending on litter species and ecosystem type after two-year’s incubation. The cellulose lost 60.1%–96.8% of the initial mass with degradation rate in the order of stream > riparian zone > forest floor. Substantial cellulose degradation occurred at the very beginning (i.e., in the first pre-freezing period) of litter decomposition. Litter initial concentrations of phosphorus (P) and lignin were found to be the dominant chemical traits controlling cellulose degradation regardless of ecosystems type. The local-scale environmental factors such as temperature, pH, and nutrient availability were important moderators of cellulose degradation rate. Although the effects of common litter chemical traits (e.g., P and lignin concentrations) on cellulose degradation across different individual ecosystems were identified, local-scale environmental factors such as temperature and nutrient availability were found to be of great importance for cellulose degradation. These results indicated that local-scale environmental factors should be considered apart from litter quality for generating a reliable predictive framework for the drivers of cellulose degradation and further on litter decomposition at a global scale. Full article

The high-grade uranium deposits in the Xiemisitan area, northwestern China, are genetically associated with the faulting of felsic volcanic or sub-volcanic rocks. Ferric iron alteration indicates that oxidizing hydrothermal fluids percolated through the rocks. In this study, we measured the gamma-ray intensities of rocks in the Xiemisitan area and we propose a hybrid method for the mapping of ferric iron alteration using concentration-area fractal modeling and spectral angle mapper. The method enables ferric iron alteration to be distinguished from potash-feldspar granitic rocks. The mapping results were integrated with structural data to assist with exploration for uranium in the study area. Using this approach, six prospective areas of mineralization were proposed. Of these areas, two anomalies with high gamma-ray intensities of 104 and 650 Uγ were identified and verified by field inspection. These observations suggest that Enhanced Thematic Mapper Plus images are a valuable tool that can improve the efficiency of uranium exploration. Full article

To analyze the association between non-alcoholic fatty liver disease (NAFLD) and the incidence of diabetic nephropathy in patients with type 2 diabetes, the incidence of diabetic nephropathy was assessed in 413 type 2 diabetic patients, by testing the 24 h urinary albumin excretion rate (UAER). The NAFLD was diagnosed based on patient’s medical history and liver ultrasound. The difference in diabetic nephropathy incidence between patients with and without NAFLD was tested by χ². Multivariate logistic regression analysis was used to assess the factors associated with diabetic nephropathy among type 2 diabetic patients. Total 363 out of 413 type 2 diabetic patients were enrolled in this study. The incidences of NAFLD and diabetic nephropathy in participants were approximately 56% (202/363) and 38% (137/363) respectively, and there was no significant difference in the prevalence of diabetic nephropathy between patients with and without NAFLD (37.1% vs. 38.5%, p = 0.787). The duration of diabetes (odds ratio [OR] 1.065, 95% confidence interval [CI] 1.014–1.120, p = 0.012), waist circumference (OR 1.077, 95% CI 1.040–1.116, p = 0.000), and fasting blood glucose (FBG; OR 1.136, 95% CI 1.023–1.1262, p = 0.017) were significantly associated with diabetic nephropathy, whereas sex, high blood pressure, total cholesterol (TC), triglyceride (TG), and ankle brachial pressure index (ABI) were not significantly associated with the disorder. The present results suggest that NAFLD is not related to the incidence of diabetic nephropathy in type 2 diabetes, but the duration of diabetes, waist circumference, and FBG are important factors for diabetic nephropathy in type 2 diabetes. Full article