Cold Regions Science and Technology最新文献

The multi-dimensional estimation of frost heave deformation is crucial for predicting soil deformation and the pressure generated during the freezing process. This study offers a comprehensive review and analysis of frost heave characteristics in the heat flow direction and the transverse direction to it. Based on the frost heave test results, an innovative method for calculating the anisotropic parameter has been introduced. This method includes only two parameters: one reflects the more pronounced characteristic of frost heave in the direction of heat flow, and the other represents the sensitivity of anisotropic parameters to constraint stress. Through comparative analysis with experimental results, this method can effectively express the evolution of the anisotropic frost heave with changes of the confining stress in different directions. Then, a combined thermal-hydraulic-mechanical coupling model is established, offering a way of applying the improved model. The coupling model can predict significant frost heave under conditions of sufficient water supply and effectively captures the frost heave characteristics under various temperature and stress boundary conditions. This research contributes significantly to predicting frost heave deformation in low-temperature natural gas pipelines and calculating the frozen soil pressure exerted on the pipelines.

This study delves into the complexities of frost formation on road surfaces, a phenomenon that presents significant safety hazards in transportation due to its sudden emergence and unpredictable nature. Despite advanced meteorological warning systems for snowfall and freezing rain, black ice and frost remain difficult to predict and counteract. To address this, a controlled indoor simulation experiment was designed to investigate the characteristics of road surface frosting at low temperatures.

Results from the experiment indicated that growth of the frost layer thickness follows a parabolic trend with extended freezing time yet the mass of the frost layer increases at a roughly linear rate. The data also revealed that lower temperatures expedite the phase transition of water vapor to ice, leading to faster increases in frost layer height. Additionally, the effects of air temperature and velocity on frost properties were examined. Interestingly, higher air temperatures facilitated rapid frost formation initially, but later stages displayed a plateau phase in the rate of accumulation. Furthermore, increased air velocity up to 1 m/s resulted in greater frost mass, but higher velocities diminished frost formation due to enhanced heat transfer.

In conclusion, this study offers a detailed analysis of frost layer development under controlled conditions, providing valuable insights into the environmental factors influencing this hazardous phenomenon. The findings contribute to the understanding of frost dynamics on road surfaces, with implications for improving predictive models and developing effective countermeasures for road safety during icy conditions.

A rapid freezing of a sea water droplet moving in a cold air is modeled. A droplet freezing model is a key component needed for computational forecasting of ice accretion on surfaces of ships and other equipment operating in low-temperature regions. The freezing process consists of the three stages: 1) water cooling to the incipient solidification temperature; 2) liquid solidification; 3) further freezing of the primarily solidified droplet. An icy region, being formed during the 2nd stage, initially represents a slurry, composed of ice crystals suspended in water. Further cooling is associated with an increase in the crystal concentration that at a certain threshold causes slurry transformation into a spongy (porous) ice. The solidification stage model is composed of the three coupled differential equations formulated in the moving coordinate system. All the physical and thermophysical water properties, required for modeling droplet freezing, are calculated by using the empirical correlations. The set of the equations is solved numerically. The solidification process is illustrated by computational examples for different droplet sizes and water salinities. The computed icy region thickness vs. time, as well as temperature distributions and porosities along droplet radius at different time moments are shown.

Accumulated snow and ice on road surface affect traffic operation. Anti-icing asphalt pavement is widely implemented as an active snow melting technology. However, there are few studies on anti-icing modified asphalt mortar mechanical properties and the effect of mortar materials on the interaction between modified asphalt and anti-icing filler. For this reason, this study investigated the mechanical properties of asphalt including rheological, high-temperature, fatigue and low-temperature properties through frequency and temperature scan, multiple stress creep recovery, linear amplitude scan, and single edge notched beam test. Based on this, the significant factors affecting asphalt mechanical properties were identified by analysis of variance. Subsequently, the Palierne-C-G* parameter was used to quantify the interaction between modified asphalt and anti-icing filler, and the effect of asphalt chemical structure on the interaction was revealed by Fourier Transform Infrared Spectroscopy (FTIR) test. The results indicated that the anti-icing filler significantly improved the high temperature and fatigue resistance of asphalt. Compared with SBS modified asphalt mortar, the mechanical properties of composite modified asphalt mortar were superior. The most significant factor affecting the mechanical properties of SBS modified asphalt mortar was modifier dosage, while the most significant factor affecting the composite modified asphalt mortar was crushed rubber dosage. The interaction showed a decreasing trend with the increase of frequency, while it appeared to increase and then decrease with the increase of temperature. The carbonyl functional group of asphalt correlated best with the interaction between asphalt and filler.

A universal testing machine and a 50 mm split Hopkinson pressure bar (SHPB) were used to conduct salt erosion and freeze-thaw (F-T) cycle coupling tests on cement soil specimens with 0.5% polyvinyl alcohol (PVA) fiber and without fiber in order to study the effects of salt solution and F-T cycles on the dynamic and static mechanical properties of cement soil. In four distinct solution settings (clear water, 9 g/L sodium sulphate solution, 9 g/L sodium chloride solution, and 9 g/L sodium sulphate and sodium chloride mixed solution). After F-T cycles, the cement soil specimens underwent the unconfined compressive strength (UCS) test, SHPB test, and SEM test. The findings indicate that as the number of F-T cycles increases, the dynamic and static mechanical properties of cement soil specimens decrease, and the rate of decline is rapid followed by slow. After five F-T cycles, the combined solution's unconfined compressive strength dropped to 15.91% (without fiber) and 29.41% (with fiber), respectively. After five F-T cycles, the dynamic compressive strength in sodium sulphate solution fell by 95.17% (without fiber) and 93.86% (with fiber). Fibers help to some degree by preventing salt erosion and F-T cycles. With more F-T cycles, the absorbed energy declines exponentially, and the order of the solutions' effects on the absorbed energy is: mixed sodium chloride and sodium sulphate solution > sodium chloride solution > sodium sulphate solution > clear water.

In technical areas, the prevention of atmospheric icing on structures is imperative due to safety risks and potential technical failures it poses. Recent development projects have focused on hybrid ice protection systems, combining active elements (heaters/mechanical actuators) with passive icephobic coatings. However, there is a lack of test strategies for the early development stages of these coating materials. An efficient test design for an ice wind tunnel is described here, developed to quantitatively assess the ice shedding effects facilitated by icephobic surfaces in electro-thermal ice protection systems. Dependencies on test and surface parameters are explored, laying the groundwork for defining test procedures for subsequent surface evaluations. During testing, utilizing a hydrophobic model coating, a reduction in energy of over 30% was observed compared to uncoated aluminium. This finding highlights the potential effectiveness of icephobic surfaces in mitigating icing effects. The presented test serves as a valuable tool for pre-selecting the most promising surfaces for further advanced tests, particularly those involving aerodynamic profiles within the ice wind tunnel test facility. It constitutes a vital component of a comprehensive test pyramid, encompassing ice-related tests with increasing complexity. Furthermore, the results obtained from these tests are utilised to establish correlations with surface properties, thereby enhancing our understanding of the significance of these findings. This approach provides a well-founded testing strategy for evaluating and advancing icephobic surface technologies.

The required time for producing snow avalanche maps is influenced by computation speed of simulations. Commonly, integrating terrain assessment with dynamic flow simulation aids in mapping dangerous areas for human and structural threats. This approach enables the evaluation of avalanche paths, as well as the assessment of flow rate and thickness during avalanche movement. However, the substantial computational cost of the simulation results in long calculation times when using the Central Processing Unit (CPU). In this study, a new rapid snow avalanche simulator was developed by applying massively parallel computation with the General-Purpose computing on Graphics Processing Unit (GPGPU) technique. By avoiding slower data transfer and utilizing faster memory, computational speed could be accelerated up to 80 times faster than conventional simulation using a CPU. Additionally, the rapid calculation models were validated based on the Mt. Nasu event in 2017, and pilot studies of the avalanche map of Mt. Nasu in Japan demonstrated the usefulness of the developed model for vulnerability evaluation. A total of 123 simulations were conducted for each susceptible source area, and all simulations were completed within only 6.5 h. This high-performance calculation can significantly reduce the time cost of producing and expanding conventional avalanche maps.

The investigation on the mechanical properties and damage model of rock subjected to freeze-thaw cycles (FTCs) holds significant theoretical for assessing the deformation of rock mass engineering in cold regions. When the rocks subjected to FTCs, the fracture voids of rocks increase with increasing number of FTCs, and the rocks exhibit nonlinear deformation characteristics as its fracture voids compaction. Based on the dissipation energy evolution law and distribution characteristics of rocks under loading, the critical point of rock compaction deformation was determined. A constitutive model for rock subjected to FTCs considering its fracture voids compaction was established based on macroscopic and microscopic damage levels. The rationality of the model was validated using experimental results, and a comparison was made between the calculation results of proposed model and model that not consider fracture voids compaction. The evolution properties of rock damage variable and stress under different FTCs were analyzed. The variation of model parameters with the FTCs and the influence of model parameters on the deformation characteristics of rock was analyzed.

Strain localization has always been an important subject in frozen soil mechanics and engineering. To evaluate the development of local strain and the formation of shear bands in frozen soil, uniaxial compression tests have been conducted on frozen sand at various temperatures and particle grades. The strain localization evolution law of the frozen soil is analyzed utilizing the digital image correlation (DIC) method. The test results reveal that the entire process of shear band generation, development, and formation in frozen soil can be well captured. Within the testing temperature and particle grade range in this study, in comparison to particle grade, temperature exerts a more pronounced influence on the shear band angle which increases as temperature decreases. It is discovered that the width of the shear band increases with the decrease in temperature and the increase in mean particle diameter d₅₀. Subsequently, a discrete element method (DEM) model is developed to examine the microscopic mechanical characteristics of frozen sand in uniaxial compression tests. The reliability of the DEM model is verified through comparative analysis with test results. Besides, the development law of the strain localization of the frozen soil obtained by the numerical simulation is revealed based on the quantitative analysis of the rotational angle, bonding state, and displacement of the soil particle during the shearing process.

Coastlines along the Sea of Okhotsk in Hokkaido are the southernmost regions in the northern Pacific Ocean where sea ice reaches the coast. It has been demonstrated that global warming affects and decreases the ice cover area in the Sea of Okhotsk. This study thus aims to investigate the relationship between sea ice and waves in the Sea of Okhotsk by analyzing ice cover area, sea ice volume, significant wave height and significant wave period. Additionally, we made an attempt to clarify trends in ice cover area and sea ice volume from 1989 to 2012 using satellite images. Sea ice volumes in the northern part of the Sea of Okhotsk correlate with significant wave height and significant wave period. Furthermore, ice cover area and sea ice volume have decreased since 2001 or 2002, which may enhance wave action during winter.