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Tunnels located in cold regions are vulnerable to frost damage resulting from the special atmosphere, which directly threatens the safety of the tunnel structure and operation. Frost problems of tunnels in cold regions have not been fundamentally resolved. This paper reviews design theory and the frost mitigation techniques currently used in the design, construction and maintenance of cold region tunnels. The depths of freezing and thawing and frost heaving force are the key indexes of design theory. Insulation is the main design technology used to prevent frost heaving and thawing, and the active heating technology has also been applied in practice. In construction, reducing the heat of hydration and blasting by specific winter construction techniques can prevent tunnel freeze–thaw damages. In operation, the restoration of drainage systems, the reinforcement of structures and the reinstallation of freezing-prevention systems are effective measures to treat frost problems. Finally, some constructive suggestions and opinions are put forward to improve the service performance of tunnels.

Germination characteristics and frost tolerance of seedlings are crucial parameters for establishment and invasion success of plants. The characterization of differences between populations in native and invasive ranges may improve our understanding of range expansion and adaptation. Here, we investigated germination characteristics of Ambrosia artemisiifolia L., a successful invader in Europe, under a temperature gradient between 5 and 25 °C. Besides rate and speed of germination we determined optimal, minimal and maximal temperature for germination of ten North American and 17 European populations that were sampled along major latitudinal and longitudinal gradients. We furthermore investigated the frost tolerance of seedlings. Germination rate was highest at 15 °C and germination speed was highest at 25 °C. Germination rate, germination speed, frost tolerance of seedlings, and the temperature niche width for germination were significantly higher and broader, respectively, for European populations. This was partly due to a higher seed mass of these populations. Germination traits lacked evidence for adaptation to climatic variables at the point of origin for both provenances. Instead, in the native range, seedling frost tolerance was positively correlated with the risk of frosts which supports the assumption of local adaptation. The increased frost tolerance of European populations may allow germination earlier in the year which may subsequently lead to higher biomass allocation—due to a longer growing period—and result in higher pollen and seed production. The increase in germination rates, germination speed and seedling frost tolerance might result in a higher fitness of the European populations which may facilitate further successful invasion and enhance the existing public health problems associated with this species.

The results of studies on the growth and development of black saxaul ( Haloxylon aphyllum (Minkw.) Iljin.) of various geographical origins and its relationship to the main environmental factors in order to identify the most promising climatypes for the creation of a seed base are provided. By testing 19 climatic ecotypes of saxaul, it was established that, in the first year after planting in the experimental plot, they suffered from frost, which was due to insufficient lignification of the annual growths of the southern climatic types. The preliminary permissible boundaries for zoning of saxaul seed material for the arid zone have been identified. The main growth indicators of saxaul during the growing season were analyzed, which made it possible to identify the earliest swelling of buds in Zaisan saxaul (Mongolian ecotype), as well as in saxauls introduced from Kazakhstan, Baskunchak, and Kharabali (Astrakhan oblast). The growth processes of saxaul continue throughout the summer period, but in the hottest years, growth is also observed in September. It has been established that the growth energy of saxaul increases with increasing air temperature, which is especially noticeable in southern climatic types. The dependence of shoot growth energy on the amount of precipitation in representatives of this species has not been noted. The highest water regime indicators were noted in saxaul introduced from Dosang (Astrakhan oblast), which characterizes them as the most drought-resistant biotypes. The crops created from northern reproduction seeds showed the highest frost resistance. The adaptation of saxaul to new growing conditions is demonstrated by its good fruiting, growth in height, increase in the diameter of the trunk and crown, and high biomass indicators. Damage to experimental plants by pests and diseases was noted by the authors only during dry and hot periods, mainly in saxaul climatypes from Kazakhstan and introduced species; no damage was noted in southern climatypes. Observations of the state of the saxaul in the conditions of the Astrakhan Trans-Volga region showed the prospects of creating its seed base in geographical cultures.

Frost-resistant rubbers retain their highly elastic properties over a wide temperature range. They are used in various friction units (e.g., seals), but their high friction coefficient and low wear resistance lead to the need for frequent replacement. In this paper, we propose applying thin (several hundred microns) UHMWPE coatings to formed rubber rings. The application technology depends on the required coating thickness. Friction tests of the coatings and pure UHMWPE were performed using the ball-on-disk (unidirectional sliding) scheme for various loads and velocities. In the experiments, the friction coefficients and temperatures near the contact area were determined. Friction tracks were studied using microscopy methods. The sliding contact of the ball and the two-layer material was modeled to obtain the dependences of the deformation component of friction on the sliding velocity for coatings of different thicknesses. UHMWPE is sensitive to frictional heating, so the thermal problem of determining the temperature in the contact area was also solved. It is shown that the minimum friction coefficient occurs for coatings with a thickness of 600 μm. At the same time, in the case of the 300 μm coating, the surface of the friction track is practically no different from the initial one. Thus, the studied combination of polymers provides antifrictional properties and wear resistance to the surface layer while maintaining the damping properties of rubber.

This paper presents the results of studies aimed at identifying statistical relationships between the landscape structure and variability in Siberian stone pine ( Pinus sibirica ) increments in the permafrost–hillocky northern-taiga landscapes of Western Siberia (Nadym River basin). Dendrochronologies of Siberian stone pine growing on frost mounds of different types are compiled. Principal component analysis is applied to obtain independent variables that describe the site and landscape structure of the territory. Cores from 512 trees growing on 23 frost mounds are analyzed. The following methods are used: crossdating, dendrochronological standardization, and the elimination of monotonic trends for each tree. Results of the classification of Sentinel satellite images were used to calculate the proportions of lakes, forests, sparse forests, floating bogs, and flat–hillocky peat bogs, with the radius of the vicinity of a frost mound of 100‒2000 m. Correlation, dispersion, and regression analyses are used in the analysis of the dependence of the median increment on the characteristic of the mound site and landscape neighborhoods. It has been established that on high mounds the variability in increments is higher on tops than on slopes, whereas the situation is often reversed on low mounds. It is also found that the tops and slopes of the frost mounds respond differently to climatic fluctuations depending on the landscape structure and the height of the mound: the close proximity of lakes reduces the variability of phytoproductive functioning on the summit surfaces. It is revealed that the sensitivity of Siberian stone pine growth to temperature fluctuations increases with an increase in the diversity of the facies structure caused by the development of thermokarst subsidence and cryogenic cracks.

Freeze-thaw processes in soils, including changes in frost and thaw fronts（FTFs）, are important physical processes. The movement of FTFs affects soil hydrothermal characteristics, as well as energy and water exchanges between the land surface and the atmosphere and hydrothermal processes in the land surface. This paper reduces the issue of soil freezing and thawing to a multiple moving-boundary problem and develops a soil water and heat transfer model which considers the effects of FTF on soil hydrothermal processes. A local adaptive variable-grid method is used to discretize the model. Sensitivity tests based on the hierarchical structure of the Community Land Model（CLM） show that multiple FTFs can be continuously tracked, which overcomes the difficulties of isotherms that cannot simultaneously simulate multiple FTFs in the same soil layer. The local adaptive variable-grid method is stable and offers computational efficiency several times greater than the high-resolution case. The simulated FTF depths, soil temperatures, and soil moisture values fit well with the observed data, which further demonstrates the potential application of this simulation to the land-surface process model.

In this study, backpropagation neural network (BPNN) and generalized regression neural network (GRNN) approaches are used to predict the frost-heaving ratio (FR) of the saline soil specimen collected from Nong’an, Western Jilin, China. Four variables, namely, water content (WC), compactness, temperature, and content of soluble salts (CSS), are considered in predicting FR. A total of 360 pieces of data, collected from the experimental results, in which 30 pieces of data were selected randomly as the testing set data and the rest of the data were treated as the training set data, are applied to develop the prediction models. The predicted data from the models are compared with the experimental data. Then, the results of the two approaches are compared to obtain a relatively reliable model. Results indicate that the prediction model for the FR of saline soil in Nong’an can be successfully established using the GRNN method. Four new GRNN models are constructed for sensitivity analysis to assess the influence degree of the influencing factors, and the results indicate that water content is the most influential variable in the FR of the saline soil specimen, whereas content of soluble salts is the least influential variable.

Climate can be understood both as a resource and a motivation for tourism. This study focuses on the second issue trying to establish the sensitivity to weather anomalies of the outbound flows from United Kingdom, the third biggest international tourist spender country. Using transfer function models it is possible to analyze the significance of the short-term weather conditions in the determination of outbound British flows and simulate the effects of different climate change scenarios. Results show how mean temperature, heat waves, air frost and sunshine days are the weather variables that can be significantly related to the dynamics of the outbound British flows time series.

The main objective of this study is to present a method of determining viscoelastic deformation monitoring index of a Roller-compacted concrete (RCC) gravity dam in an alpine region. By focusing on a modified deformation monitoring model considering frost heave and back analyzed mechanical parameters of the dam, the working state of viscoelasticity for the dam is illustrated followed by an investigation and designation of adverse load cases using orthogonal test method. Water pressure component is then calculated by finite element method, while temperature, time effect, and frost heave components are obtained through deformation statistical model considering frost heave. The viscoelastic deformation monitoring index is eventually determined by small probability and maximum entropy methods. The results show that (a) with the abnormal probability 1% the dam deformation monitoring index for small probability and maximum entropy methods is 23.703 mm and 22.981 mm, respectively; thus the maximum measured displacement of the dam is less than deformation monitoring index, which indicates that the dam is currently in a state of safety operation and (b) the obtained deformation monitoring index using orthogonal test method is more accurate due to the full consideration of more random factors; the method gained from this study will likely be of use to diagnose the working state for those RCC dams in alpine regions.