High-cold Areas Research Articles

Analytical study on plastic loosening zone of weak surrounding rocks tunnel in high cold areas

AbstractThe analysis of plastic loosening zone of tunnels with cold condition, high in situ stress, and weak stratum is the key scientific problem of tunnel construction in cold areas. Based on the unified strength theory and considering the coupling effect of high in situ stress and low‐temperature field, the analytical model of the plastic loosening zone of tunnel surrounding rocks was proposed, and the influence laws of physical parameters (initial ground stress, freezing temperature, excavation radius, and intermediate principal stress) was explored. The results illustrate that: (1) with the coupling of low temperature and stress fields, the in‐situ stress has a more significant effect on the radius of the plastic loosening zone of the tunnel surrounding rocks, showing a nonlinear correlation. When the in situ stress is small, the influence of the temperature field on the radius of the plastic loosening zone is more obvious. (2) The radius of the plastic loosening zone of the tunnel surrounding rocks increases synchronously with the excavation radius and gradually decreases with the increase of the intermediate principal stress. (3) The greater the temperature difference in the low‐temperature field, the tunnel stability has a more significant response to the intermediate principal stress and is positively correlated with the coefficient of the intermediate principal stress. (4) In the actual project, the proposed model can well describe the mechanical behavior and deformation characteristics of tunnel surrounding rocks in low‐temperature environment, showing applicability. The research results are expected to provide a theoretical basis for the study of tunnel stability in cold areas.

Research on the effectiveness of second-child subsidy policy in high-cold areas based on multi-level model

Research on the effectiveness of second-child subsidy policy in high-cold areas based on multi-level model

Dynamic deformation and meso-structure of coarse-grained saline soil under cyclic loading with freeze-thaw cycles

The cumulative deformation properties of subgrade soil under cyclic traffic loads are critical for optimizing pavement structure design and ensuring long-term highway structural performance. This study aims to investigate the coupling effect of freeze-thaw cycles and cyclic loads on the cumulative deformation behaviors and meso-structure of coarse-grained saline soil (CGSS) subgrade filling in high-cold areas. Dynamic triaxial tests and computed tomography (CT) scanning were conducted to analyze the CGSS under different working conditions. The research focused on the dynamic deformation development and damage evolution under varying freeze-thaw cycles and load amplitudes. The research results show that the cumulative deformation behavior of CGSS under cyclic loading is relatively sensitive to the freeze-thaw process. The cumulative dynamic strain increases as the freeze-thaw cycles, with a critical freeze-thaw cycle number of five. The stable cumulative dynamic strain curve exhibits clear three-stage characteristics when plotted in semi-log coordination, with critical loading cycles at 20 and 1,000. After 10–100 loading cycles, the cumulative strain curve quickly shows failure. The CGSS’s low density and pore regions greatly increase after a freeze-thaw cycle. The rise in dynamic stress amplitude notably affects the bonding between soil particles and crystalline salts. The coupling effect of the freeze-thaw cycle and dynamic activity exacerbates the deterioration of soil structure, resulting in variations in CT values within the scanning layer in the final state.

Temperature sensitivities of vegetation indices and aboveground biomass are primarily linked with warming magnitude in high-cold grasslands

Incessant argument on whether temperature sensitivity of aboveground biomass is primarily linked with temperature itself (local air temperature and increased magnitudes in air temperature) or other environmental variables restrains our capability to exactly forecast upcoming alterations in grass yield and high-quality development of animal husbandry in high-cold areas. Consequently, since May 2010, a field warming trial with open-top containers was achieved in high-cold grasslands at three elevations (i.e. 4313, 4513 and 4693 m) of the Tibet. The temperature sensitivities of normalized different vegetation indices (Q1_NDVI), soil adjusted vegetation indices (Q1_SAVI) and aboveground biomass (Q1_AGB) were detected in 2014–2015 and 2017–2018. Temperature itself had the greatest exclusive impacts on the Q1_NDVI, Q1_SAVI and Q1_AGB. Vegetation indices itself or aboveground biomass itself had the second greatest exclusive impacts on the Q1_NDVI, Q1_SAVI or Q1_AGB. The exclusive impact of vegetation indices itself or aboveground biomass itself was less than one-tenth that of temperature itself. Water availability and elevation & duration (elevation and warming length) only had exclusive impacts on the Q1_NDVI and Q1_SAVI. The total exclusive impact of water availability and elevation & duration on the Q1_NDVI or Q1_SAVI was around 11–12 % equivalent to that of temperature itself. Vegetation indices/aboveground biomass itself, water availability and elevation & duration had interactive impacts with temperature itself on the Q1_NDVI, Q1_SAVI or Q1_AGB. Compared to local air temperature, increased magnitudes in air temperature had the greater exclusive effects on the Q1_NDVI, Q1_SAVI and Q1_AGB. Consequently, temperature sensitivities of vegetation indices, and aboveground biomass were primarily linked with temperature itself (especially warming magnitude), and adjusted by water availability, vegetation indices/aboveground biomass itself, elevation and warming length in high-cold grasslands of the Tibet.

Climate Adaptation and Indoor Comfort Improvement Strategies for Buildings in High-Cold Regions: Empirical Study from Ganzi Region, China

The improvement of building and living conditions in high-cold areas has always been an issue worthy of attention, but there is currently no research using field survey data for evaluation. The Ganzi region, based in the western plateau of China, is a typical example for such a study. Restricted by factors such as natural conditions and economic level, the winter indoor thermal environment of western plateau houses is generally poor. Taking the new residential houses in the Ganzi region as a case study, the authors of this paper conducted field research and analyses. First, the authors analyzed the construction technology and functional layout of the building through thermal environment testing and investigation; second, the authors analyzed the user’s activity path according to the production and lifestyle; thirdly, the authors comprehensively evaluated the indoor thermal comfort through questionnaires and a predicated mean vote (PMV)-predicted percentage dissatisfied (PPD) evaluation model. The research results showed that: (1) the construction technology, functional layout, and temperature distribution of the new residential building were consistent with the user’s activity path, which could effectively improve thermal insulation ability and thermal comfort; (2) compared to the developed eastern regions, the users in the building showed a stronger tolerance and wider acceptable temperature range in the extreme climate environment; and (3) under certain cooperative work conditions, an indoor temperature of 10–14 °C could meet basic thermal environment requirements and thus lower the limits of the standards. The author’s method was proven to be more resilient than current standards in dealing with climate change. Therefore, this research can provide a practical reference for the improvement of peoples’ living conditions and sustainable development in cold regions and other harsh areas.

Simulated Long-Term Vegetation–Climate Feedbacks in the Tibetan Plateau

The Tibetan Plateau (TP) is an important region of land–atmosphere interactions with high climate variability. In this study, an atmosphere–vegetation interaction model was applied to explore the possible responses of vegetation to climate warming, and to assess the impacts of land cover change on the land surface physical processes across the TP. Results showed that long-term warming over the TP could influence vegetation growth via different mechanisms. Most likely, increased temperature would enhance the physiological activity in most high cold areas on the TP, whereas high temperature would inhibit vegetation growth by increasing respiration in areas with favorable water and temperature conditions. In addition, for areas where the climate is warmer but not wetter, higher temperature could influence photosynthesis via the moisture condition of the vegetation rather than by modulating respiration. Numerical simulations demonstrated that vegetation could control the land surface–atmosphere energy balance effectively. The change of land cover from vegetated land to desert steppe decreased the net radiation absorbed by the surface, weakening the surface thermal effects, and reducing sensible and latent heat fluxes. Furthermore, sensitivity simulations also revealed that global warming would likely accelerate vegetation growth in most areas of the TP, resulting in increased surface heat flux.

Ensilage of oats and wheatgrass under natural alpine climatic conditions by indigenous lactic acid bacteria species isolated from high-cold areas.

Five different species of selected broad-spectrum antibiotic lactic acid bacteria isolated from extremely high–cold areas were used as starters to ferment indigenous forage oats and wheatgrass under rigid alpine climatic conditions. The five isolates were Lactobacillus plantarum QZ227, Enterococcus mundtii QZ251, Pediococcus cellicola QZ311, Leuconostoc mesenteroides QZ1137 and Lactococcus lactis QZ613, and commercial Lactobacillus plantarum FG1 was used as the positive control and sterile water as the negative control. The minimum and maximum temperatures were −22°C and 23°C during the fermentation process, respectively. The pH of wheatgrass silage fermented by the QZ227 and FG1 inocula reached the expected values (≤4.15) although the pathogens detected in the silage should be further investigated. All of the inocula additives used in this study were effective in improving the fermentation quality of oat silage as indicated by the higher content of lactic acid, lower pH values (≤4.17) and significant inhibition of pathogens. QZ227 exhibited a fermentation ability that was comparable with the commercial inoculum FG1 for the whole process, and the deterioration rate was significantly lower than for FG1 after storage for 7 months. The pathogens Escherichia coli, mold and yeast were counted and isolated from the deteriorated silage. E. coli were the main NH3-N producer while F. fungi and yeast produced very little.

Influence of Moisture Content to the Freeze-Thaw Performance of Roadbed in High-Cold Areas

Frost-heave and thaw-settlement of roadbed soil in highway will influence directly the durability, safe traffic flow and construction & maintenance costs in high-cold areas, therefore, recognizing and analysing the common embankment technologies of highway roadbed in high-cold areas accurately is significant to the effective controlling of project invest and the highway construction with limited funds in minority areas. The relations of Moisture Content and the freeze-thaw performances of roadbed fillers, subgrade soil were got respectively by experiments, and the results shows: Moisture Content has larger influence on the frost-heave and thaw-settlement performance of the soil. During the embankment of roadbed, the Moisture Content of fillers should be controlled nearby the optimum Moisture Content. The frost-heave and thaw-settlement occurs mainly in the subgrade soil, controlling the Moisture Content of subgrade soil is very important to improve the up-limit of frozen-soil, keep the stability of frozen-soil, control the thaw-settlement of roadbed and get rid of the roadbed diseases.

Influence of Moisture Content to the Freeze-Thaw Performance of Roadbed in High-Cold Areas

Frost-heave and thaw-settlement of roadbed soil in highway will influence directly the durability, safe traffic flow and construction & maintenance costs in high-cold areas, therefore, recognizing and analysing the common embankment technologies of highway roadbed in high-cold areas accurately is significant to the effective controlling of project invest and the highway construction with limited funds in minority areas. The relations of Moisture Content and the freeze-thaw performances of roadbed fillers, subgrade soil were got respectively by experiments, and the results shows: Moisture Content has larger influence on the frost-heave and thaw-settlement performance of the soil. During the embankment of roadbed, the Moisture Content of fillers should be controlled nearby the optimum Moisture Content. The frost-heave and thaw-settlement occurs mainly in the subgrade soil, controlling the Moisture Content of subgrade soil is very important to improve the up-limit of frozen-soil, keep the stability of frozen-soil, control the thaw-settlement of roadbed and get rid of the roadbed diseases. CLC: U416.1 Document code: B

Chemical Constituents of Gentiana algida

There are about 240 species of the Gentiana genus grown in China, Gentiana algida Pall. is broadly distributed in the alpine zone of the world. In China, it is a little-investigated medicinal plant, that grows mainly in high cold areas such as Tibet, Sichuan, Xinjiang, Qinghai, and Jilin Provinces [1]. To the best of our knowledge, no work has been reported on the chemical constituents of Gentiana algida. As part of our continuing research on Gentiana algida Pall. [2], we have isolated six compounds from G. algida for the first time. The air-dried plants of G. algida were bought from Kumbum Monastery Tibetan Hospital in Qinghai Province of China in October of 2009 and was identified by Prof. Guo-Liang Zhang, Lanzhou University. The powdered G. algida (4.5 kg) was extracted by ethanol (30 L 4, each extraction lasting 7 days) at room temperature. The EtOH extract was concentrated under reduced pressure to give a residue (798 g), which was sequentially partitioned with petroleum ether (90–100 C) (1.0 L 4), EtOAc (1.0 L 4), and n-BuOH (1.0 L 4). The n-BuOH fraction (238 g) was chromatographed on a macroporous resin column (6.5 150 cm) and eluted with H2O–EtOH (90:10, 75:25, 50:50, 25:75, 5:95, 0:100, v/v) gradientwise and acetone to yield seven fractions (Fr. 1–Fr. 7) according to TLC analysis. Fraction 2 (3 g) was re-treated on a polyamide (60–100 mesh, 100 g) column and eluted with H2O–MeOH (5:1, v/v) to obtain 1 (25 mg), then futher eluted with H2O–MeOH (1:1, v/v) to obtain 2 (10 mg). Fraction 4 (0.5 g) was re-treated on a LH-20 (20–150 m, 30 g) column and eluted with H2O–MeOH (1:1, v/v) to obtain 3 (15 mg). Fraction 5 (1.5 g) was chromatographed on a silica gel (200–300 mesh, 50 g) column and eluted with CHCl3–MeOH (10:1, v/v) to obtain 4 (15 mg). Fraction 7 (1 g) was re-treated on a silica gel (200–300 mesh, 30 g) column and eluted with PE–EtOAc (10:1, v/v) to obtain coarse crystals of compounds 5 (30 mg) and 6 (20 mg), then recrystalled with petroleum ether to obtain 5 (15 mg) and 6 (10 mg). Isoscoparin (1), yellow powder, C22H22O11. ESI-MS m/z 461 [M – 1] +. 13C NMR (100 MHz, DMSO-d6, TMS, , ppm): 163.8 (C-2), 103.2 (C-3), 182.0 (C-4), 160.7 (C-5), 108.9 (C-6), 163.4 (C-7), 93.8 (C-8), 156.3 (C-9), 103.3 (C-10), 121.4 (C-1 ), 120.4 (C-2 ), 148.1 (C-3 ), 150.8 (C-4 ), 115.8 (C-5 ), 110.2 (C-6 ), 73.1 (C-1 ), 70.3 (C-2 ), 79.0 (C-3 ), 70.6 (C-4 ), 81.6 (C-5 ), 61.5 (C-6 ), 56.0 (OCH3-3 ) [3]. Gentiopicroside (2), white powder, C16H20O9. ESI-MS m/z 379 [M + Na] +. 1H NMR (400 MHz, DMSO-d6, TMS, , ppm, J/Hz): 7.38 (1H, s, H-3), 5.62 (1H, m, H-6), 5.60 (1H, d, J = 3.0, H-1), 5.19 (1H, m, H-10), 5.15 (1H, m, H-10), 5.04 (1H, m, H-7), 4.96 (1H, m, H-7), 4.48 (1H, d, J = 8.0, H-1 ), 3.14 (1H, t, J = 8.8, H-9). 13C NMR (100 MHz, DMSO-d6, TMS, , ppm): 96.7 (C-1), 149.1 (C-3), 103.5 (C-4), 125.1 (C-5), 116.4 (C-6), 70.1 (C-7), 134.1 (C-8), 44.5 (C-9), 116.2 (C-10), 163.1 (C-11), 98.9 (C-1 ), 73.0 (C-2 ), 77.4 (C-3 ), 69.4 (C-4 ), 76.7 (C-5 ), 61.3 (C-6 ) [4]. 3,6,4 -Trimethoxy-5,7-dihydroxyflavone (3), yellow powder, C18H16O7 [5]. -Sitosterol (4), white needles identical to an authentic sample. 10 -Hydroxy-7(11)-eremophilen-12,8 -olide (5), white needles, C15H22O3. EI-MS m/z 250 [M] +, 232, 126, 125, 109. 1H NMR (400 MHz, CDCl3, TMS, , ppm, J/Hz): 2.6 (1H, d, J = 14.0, H-6 ), 2.43 (1H, d, J = 14.0, H-6 ), 5.01 (1H, m, H-8), 2.15 (1H, dd, J = 7.2, 12.8, H-9 ), 1.96 (1H, dd, J = 11.2, 12.8, H-9 ), 1.81 (3H, s Me-13), 1.06 (s, Me-14), 0.84 (3H, d, J = 6.4, Me-15). 13C NMR (100 MHz, CDCl3, TMS, , ppm): 36.3 (C-1), 22.3 (C-2), 29.7 (C-3), 33.5 (C-4), 44.9 (C-5), 31.7 (C-6), 161.4 (C-7), 78.7 (C-8), 40.9 (C-9), 74.9 (C-10), 120.5 (C-11), 175.2 (C-12), 8.2 (C-13), 14.7 (C-14), 16.0 (C-15) [6].