Artificial ground freezing of underground mines in cold regions using thermosyphons with air insulation

Current practice of underground artificial ground freezing(AGF)typically involves huge refrigeration systems of large economic and environmental costs.In this study,a novel AGF technique is proposed deploying available cold wind in cold regions.This is achieved by a static heat transfer device called thermosyphon equipped with an air insulation layer.A refrigeration unit can be optionally integrated to meet additional cooling requirements.The introduction of air insulation isolates the thermosyphon from ground zones where freezing is not needed,resulting in:(1)steering the cooling resources(cold wind or refrigeration)towards zones of interest;and(2)minimizing refrigeration load.This design is demonstrated using well-validated mathematical models from our previous work based on two-phase enthalpy method of the ground coupled with a thermal resistance network for the thermosyphon.Two Canadian mines are considered:the Cigar Lake Mine and the Giant Mine.The results show that our proposed design can speed the freezing time by 30%at the Giant Mine and by two months at the Cigar Lake Mine.Further,a cooling load of 2.4 GWh can be saved at the Cigar Lake Mine.Overall,this study provides mining practitioners with sustainable solutions of underground AGF.

Strategies and Economic Benefit Analysis for Productive Landscape of Rape Flower Sea in Cold Regions

The cold regions are located in high latitudes and cold climates.The local excellent ornamental plant resources are relatively scarce.The plant species that are suitable for both ornamental and productive benefits of landscape of flower sea construction are also even fewer.Therefore,it is imperative to introduce and screen the plant resources suitable for cold regions to create the landscape of flower sea.The rape,an oilseed crop,was used as a research object in order to create a productive flower landscape with both ornamental and economic values in cold regions.Four rape flower varieties,Qingza No.5,7,9,and 11,were introduced from Qinghai Hufeng Agricultural Science and Technology Group Co.,Ltd.They were planted in the experimental practice base of Northeast Agricultural University in three batches.Development characteristics and seed yield of rape flowers on different sowing dates were studied.The fuzzy probability method was used to comprehensively evaluate the varieties.The results showed that the rape flowers grew well in Harbin City during the experimental sowing period,which could form a good landscape of flower sea and had a considerable rapeseed yield.It could be widely used in cold urban and rural areas,such as Harbin City.In view of the experimental results,the strategies of creating a productive landscape of rape flower sea were proposed and the economic benefits were analyzed.It could change the status quo of a uniform landscape of flower sea in cold regions,help the development of rural tourism,and promote local economic income.

Dynamic response characteristics of a circular lined tunnel under anisotropy frost heave of overlying soil at the tunnel portal section in cold regions

The rapid development of traffic engineering in cold regions and its consequent problems need to be considered.In this paper,the dynamic response characteristics of the tunnel portal section in cold regions with harmonic load acting on the lining were studied in the frequency domain.The lining is in close contact with the frozen soil,and there is relative movement between the frozen and unfrozen soil due to the phase change.The analytical solution of the vibration of tunnel portal section caused by the harmonic load acting on the lining was derived under the consideration of the anisotropy frost heave of overlying soil.Based on the continuity conditions and boundary conditions,the undetermined coefficients were obtained,and the analytical solutions for different medium displacements and stresses of the cold-region tunnel system were acquired.The vertical pressure coefficient was equivalently simplified as a variable that could be used to replace the thickness of the overlying soil above the tunnel.The analysis of the parameter model shows that the change of the medium parameters(lining,frozen,and unfrozen soil)affects the circumferential stresses,the radial displacements and their peak frequencies of the soil.For example,the increase of density ratio of tunnel lining to frozen soil decreases the radial stresses of the frozen and unfrozen soil;the increase of volumetric frost heaving strain of the frozen soil increases the radial displacements of the frozen surface and decreases the stability of the frozen surface;the increasing of thickness of the frozen soil significantly reduces the radial displacement of unfrozen soil at dimensionless radius η=4.5 compared with that of frozen soil at η=1.5.

Correlation analysis of longitudinal cracks and vertical deformation within asphalt pavement of cold regions

The asphalt pavement longitudinal crack is a common distress in cold regions,resulting from uneven deformation of the subgrade.Analysis of the correlation law between uneven deformation and crack distress is of positive significance for understanding the mechanism of crack initiation,and putting forward treatment measures.In view of the complexity of longitudinal crack inducement and road surface deformation,the grey relational method was used to analyze this relationship.Through long-term monitoring of the vertical deformation data of typical road sections,the vertical deformation law of the pavement surface and its deformation characteristics under the action of temperature field are analyzed.Parameters such as vertical relative deformation,vertical relative deformation rate and vertical differential deformation VDSr were constructed to describe vertical deformation characteristics.Typical distribution characteristics of longitudinal fractures and their length and distribution characteristics are also described.The grey correlation analysis theory was utilized to analyze the relationship between deformation characteristics of sections,cross sections and monitoring points and longitudinal crack characteristics(length and location).The analysis reveals a linear positive correlation or a high correlation between several indicators.This study can provide a deeper understanding of the occurrence and development mechanism of longitudinal cracks in asphalt pavement of cold areas,and give references for the research of road engineering structure,materials and distress prevention.

The effect of living environment on developmental disorders in cold regions

Developmental disorders(DDs)are a kind of chronic maladies,which can cause serious irreversible detriment to children’s physical and mental health.It is predominantly regulated by the interaction of environment and heredity.Cold regions are mainly located in the high latitudes of China.Their living environment is characterized by frequent cold wave,huge temperature difference,severe air pollution,high calorie diet,less exercise,smoking,drinking,etc.In recent years,substantial advances have been made in studies of the correlation between the living environment features in cold regions and the DDs.Accordingly,this article reviews the impact of the peculiar living environment of cold regions on DDs,with a view to provide fresh prevention strategies for reducing the morbidity of DDs in China cold regions by ameliorating living environment.

Characterization of Reverse Thermo-sensitive Genic Male Sterile Lines in Cold Regions of China

Yannong S, a reverse thermo-sensitive genic male sterile （TGMS） line, is sterile at high temperature and fertile at low temperature. In the present study, the fertility of Yannong S and the japonica reverse TGMS lines derived from it was in- vestigated in Harbin, Heilongjiang from 2013 to 2015. The results showed that Yan- nong S was completely male sterile in July and August （the hottest months of the year in Harbin）, and the seed setting rate of bagged panicles was 0. We also in- ferred that the critical temperature for inducing the sterility of Yannong S was higher than 28 ℃. Most of the japonica reverse TGMS lines derived from Yannong S were completely aborted in July and August, with a seed setting rate of 0. It can be con- cluded that the reverse TGMS lines derived from Yannong S are genetically stable lines that have a long period of sterility in cold regions, so they may be the ideal genetic materials for the development and in-situ seed production of japonica hybrid rice.

Structural analysis and design of frost resistance function for subgrade of high-speed railway ballasted track in cold regions

According to the technical characteristics of short fixed wheelbase of a high-speed carriage, a subgrade-track integrated space mechanical response analysis model is proposed for trains under the action ofbiaxial load after the comparison of the stress distribution characteristics of the ballast track subgrade bed structures for high-speed railway under the action of uniaxial load and biaxial load. The loading threshold value （high-cycle long-term dynamic strength） under the circum- stance where the cumulative deformation of subgrade structure gradually develops and finally reaches the convergent state, and its relationship with the foundation coefficient K30 were deduced, based on the characteristics of cumulative defor- mation evolution obtained from the unit structure filling model test under the action of cyclic loading. In view of structure stability and frost resistance requirements of the railway subgrade in cold regions, technical conditions to maintain good service performance of subgrade structure of high-speed railway ballasted track are discussed and analyzed. Study results show that the additive effect manifests itself obviously for railway train bogies under the action of biaxial load than uni- axial load, which has a significant dynamic effect on the subgrade bed bottom and a slight effect on the surface layer. Thus, the adoption of a biaxial load model in the design of a high-speed railway subgrade accurately reflects the vehicle load. Pursuant to the structure design principle, the design method of the subgrade structure of high-speed railway ballasted track is proposed to meet the technical requirements such as structural strength, bearing stiffness and high-cyclic and long-term stability. Technical indicators are obtained for the variation of thickness of the surface layer of reinforced sub- grade bed in the double-layer subgrade mode along with the change of K30 at the subgrade bed bottom. The double-layer structure mode of ＂closure on the upper layer and drainage on the lower layer＂ was proposed in order to meet the water- proofing and drainage requirements of the upper layer of the subgrade bed in cold regions. A dense-framework graded gravel filler with weak water permeability at a coefficient of 10 4 cm/s is used on the upper layer and the void-framework graded gravel filler at the water permeability coefficient of 10 2 cm/s is adopted on the lower layer.

Study on the Improvement Strategies of Physical Environment for Square in Severe Cold Regions' Rural Areas

To improve the comfortable physical environment for square in severe cold regions' rural areas. This paper applies the methods of questionnaires,field testing and statistical analysis to compare and analyze two different square cases of Qingyunpu in Liaoning Province,and conclude the main factors which affect the physical environmental comfort. The improvement strategies for physical environment of rural square are put forward from the aspects of site selection,road position,orientation,landscape design,and ground pavement material selection,aiming to provide the design basis for the physical environment of square in severe cold regions' rural areas.

Population Construction and Super-high Yield Characteristics of Japonica Super Rice in Cold Regions

[Objective] This study was conducted to construct a super-high yield population of Japnica rice in cold regions of North China and to explore its characteristics. [Method] The super rice variety Longjing 21 was selected as the experimental material. Different row spacing（two levels）, plant spacing（three levels） and seedling number per hill（three levels） were designed in field trials. Then, the growth stages,dry matter accumulation, leaf area, yield and yield components of these different treatments were measured. [Result] Rice yield had significantly negative correlation with plant spacing and row spacing, but no significant correlation with seedling number per hill. Rice yield was mainly affected by plant spacing, and less affected by seedling number per hill. The best recommended specifications for plant spacing of super rice variety Longjing 21 were 24 cm for row spacing, 12 cm for plant spacing and five seedlings per hill, and the expected yield was 10 473.0 kg/hm^2.The increased number of total spikelets（4.5×108hm2or more） in populations was the major reason for high yield. Super-high yield populations had fewer tillers at the early growth stage and achieved the expected number of productive tillers at critical leaf-age（June 25）, and tiller number peaked at jointing stage（July 6） and was about 1.2 times of the expected number. The percentage of productive tillers in total tillers of super-high yield population was more than 85% at heading stage. At middle growth stage（from jointing to heading stage）, the dry matter accumulation, leaf area index（LAI） at heading stage, effective leaf area, spikelet number of population,spikelet number per leaf area unit（cm2）, and culm-sheath weight per stem of super-high yield population were significantly higher than those of other populations.At late growth stage（from heading to maturity stage）, the leaf area decreasing rate of super-high yield population was significantly smaller than that of other populations. At late growth stage（from heading to maturity stage）, the leaf area decreasing rate, crop growth rate, net assimilation rate, biomass accumulation, number of filled grains per leaf area unit（cm^2） and grain weight per leaf area unit（cm^2） of high-yield population were significantly higher than those of other populations. Output and translocation of dry matter（weight per stem and sheath and total filling rate at maturity） from heading to milky stage of super-high yield population were significantly higher than those of other populations. [Conclusion] The characteristics of superhigh yield rice in cold region of North China are enriching the amount of actual filling of sink through improving photosynthetic efficiency from heading to maturity stage on the basis of enough panicle numbers.

Rationale for creation of capillary breaking layers in cold regions subgrade by pressure injection of waterproofing compounds

In the presents work,the authors have carried out a field study of moisture transfer processes in highway subgrades in a cold region during freezing and laboratory experiments on freezing samples of silicified soils used as a capillary barrier.The study showed that the creation of a capillary barrier from an injected solution,blocking the access of groundwater to the freezing zone,will reduce the amount of heaving to permissible values.Based on the results of laboratory studies,an exponential dependence of the relative deformation due to frost heaving on the relative height of soil silicatization in the freezing zone has been established.For creating a capillary barrier in the already existing subgrade,the authors have proposed designs of injection-silicified soils and substantiated the use of such soils.

Discussion on pile axial load test methods and their applicability in cold regions

The measurement of pile axial load is of great significance to determining pile foundation design parameters such as skin friction and end bearing capacity and analyzing load transfer mechanisms.Affected by the temperature and ice content of frozen ground,the interface contact relationship between pile foundation and frozen soil is complicated,making pile axial load measurements more uncertain than that in non-frozen ground.Therefore,it is necessary to gain an in-depth understanding of the current pile axial load test methods.Four methods are systematically reviewed:vibrating wire sensors,strain gauges,sliding micrometers,and optical fiber strain sensors.At the same time,the applicability of the four test methods in frozen soil regions is discussed in detail.The first two methods are mature and commonly used.The sliding micrometer is only suitable for short-term measurement.While the Fiber Bragg grating(FBG)strain gauge meets the monitoring requirements,the Brillouin optical time-domain reflectometer(BOTDR)needs further verification.This paper aims to provide a technical reference for selecting and applying different methods in the pile axial load test for the stability study and bearing capacity assessment of pile foundations in cold regions.

Ice-and cryogel-soil composites in water-retaining elements in embankment dams constructed in cold regions

There are a number of serious problems connected with building and repairing water-reining elements in embankment dams in cold regions. One of them is the difficulty in finding inexpensive clay materials with the necessary structural properties and using them in the winter. Another is the cracks that appear in the upper part of a dam when the core freezes to the banks, and leakage along the cracks threatens to desWoy the dam. Still another is the process of erosion at the bottom of the core which may occur through fissures in the rock foundation of a dam and in transport constructions. Also, the behaviour of water-retaining elements during eazthquakes is unreliable. All of these problems can be solved by using iceand cryogel-soil composites created by cryotropic gel formation （CGF）. Our laboratory investigations demonstrate that the materials proposed for water-retaining elements have the necessary permeable, plastic, thermophysical, and slrength properties to solve all of these problems. Certain consmactious of water-retaining elements which may prove to be both safe and cost-effective are proposed. However, these iceand cryogel-soil composites need to be field-validated before they are used in dams and transport structures in cold regions.

Numerical simulation of dynamic response of subgrade under moving heavy truck in cold regions

This paper reports on the dynamic response of highway subgmde under moving heavy Wuck in cold regions. Numerical simulations are performed in two stages. In the first stage, the moving heavy truck vibration, induced by mad roughness, is calculated through a three-dimensional dynamic interaction model of heavy tmckavement-subgrade, and the lime-histories of nodal loads on the top of the base are calculated through this model. In the second stage, a two-dimensional dynamic finite element model of the bgrade-ground system is formulated, using the calculated nodal loads from the first stage as input. The dynamic resporkse of the subgrade is validated by field measurements, and the effects of mack type, axle loading, running speed, and road roughness on the vertical dynamic slress in the unfrozen period and the spring thawing period are analyzed and discussed.

Seismic behavior of tire waste-sand mixtures for transportation infrastructure in cold regions

Tire wastes have many properties that are valuable from a geotechnical engineering perspective, such as low density, high strength, thermal insulation, energy absorption capacity, permeability, durability, compressibility, resilience, and high frictional strength. Thus, tire wastes offer good thermal characteristics in resisting frost penetration and have good drainage characteristics, being as permeable as coarse granular soil for fill materials. The many advantages of tire wastes make the material suitable for transportation infrastructure construction in cold regions. Also, tire wastes with high damping prop- erty make them a preferable admixture with sand for transportation infrastructures in seismic regions, This study aimed to determine the seismic performance of certain tire waste-sand mixtures in cold regions. A 70% sand-30% tire crumb mixture by weight （TC30） with a very high damping property was selected for analysis as an engineering material for transportation infrastructure. Small-scale shake-table tests were conducted on this material as well as on a sand-only sample under two different temperatures, 0 ℃ and 20 ℃, to simulate cold-region and moderate-temperature performance, respectively. The 1999 lzmit Earthquake Excitation （EW） （Mw = 7.4） was taken as the input motion. Test results showed that the tire waste-sand mixture at 0 ℃ showed better seismic performance than that at room temperature, suggesting that a tire waste-sand mixture in cold regions may reduce seismic hazards to infrastructure.

Research on the Limit Value of Shape Coefficient of Rural Residences in Severe Cold Regions

Shape coefficient is a significant factor accounting for building energy consumption. In order to decrease the building energy consumption of rural residence in severe cold regions,this paper from the perspective of regulating the shape coefficient limit value,applies the field survey method to statistic and analyze the shape,width and depth of rural residence in severe cold regions and concludes the distribution characteristics and scope of building area. On this basis,though calculating and analyzing the relations between shape coefficient and length-width ratio under different building areas,meanwhile comprehensive considering the building function,farmers' living mode and requirements etc,it put forward that the shape coefficient of rural residence in severe cold regions should below 0. 8. It has important significance for guiding the rural energy-saving house design and construction of severe cold regions.

Incident analyses of frost heaving failure of municipal underground gas pipelines in cold regions of northern China

In the cold regions of northern China, incidents of municipal underground gas pipeline rupture and leakage occur quite fi-equently, aaost often in winter. To prevent harm to citizen safety and property, analysis of the causes of such cracking and leakage is therefore valuable. Two incident analyses are discussed here and the reasons why most of these types of cases occur dttring winter are clarified. Fhe effects of vehicle loadings above buried pipelines are calculated and compared with the effects and calculations of frost heaving forces. We demonstrate thtit when the soil layer above a pipeline freezes rapidly, the soil generates repeated frost heaving, which exerts heaving forces on the pipeline that can result in fatigue crack propagation and ultimate pipeline failure. Therefore, the incident induced 9y frost heaving is one of the primary reasons of gas pipeline failure. Based on these analyses, we present some recommendations pertaining to the proper design, construction, and management of gas pipelines.

Use of fly ash with no water consumption for cold regions transportation infrastructure

The construction period in cold regions is very short due to problems related to excavation and use of frozen soils in embankment construction, which leads to excessive deformations upon thawing. Also, handling of compaction water is critical due to freezing temperatures. Coalburning thermal power plants are very common in cold regions to supply electricity. The inorganic part of the pulverized coal after burning produces fly ash, which is available in large volumes. Due to excavation difficulties and the poor engineering behavior of frozen soils in cold regions, the utilization of fly ash when it is readily available must be promoted. Any construction technique which utilizes alternative materials like fly ash and minimizes water consumption has a potential to extend the short construction season and even allow service and maintenance during extreme weather conditions. This paper presents two potential techniques to solve the moisture affinity of silt-sized materials like fly ash. One technique involves in-plant production of fly ash pellets using cold-bonding pelletization to manufacture aggregates of up to 40,000-~tm diameter from 15- to 60-~tm-diameter fly ash grains. Large disc pelletizers have annual production capacities of up to one million ton at a reasonable cost. The product has adequate strength for embankment construction even when no water is used and no compaction is applied. The second technique is an in situ mixing technique which uses snow instead of compaction water for fly ash. The snow is the main element in this technique to compact the embankment. Water is needed for the hydration reactions to form cementitious minerals in fly ash. The slower the hydration reaction, the greater the crystal growth of cementitious minerals. In the proposed technique, in situ snow is mixed with fly ash and is compacted on-site. The temperature increase due to the hydration reaction of fly ash upon contact with snow crystals provides water for continued long-term hydration, which results in high strength, a high void ratio, light weight, and high thermal insulation capability. The presented techniques have the potential to extend the short construction season in cold regions and will provide fill material, decreasing the need for excavation. Both techniques are well documented under laboratory conditions, the research results have been published, and the techniques are ready for field trials to assess implementability.

Advances on pathogenesis of migraine in cold regions

Migraine is a common primary headache which seriously affects the quality of patients’life due to the high prevalence and disability rate.Recent years a large number of studies have found that temperature is directly bound to migraine and migraine patients in cold regions have higher prevalence,different manifestations and poor response to the conventional therapy.We propose in this review article a new concept of migraine in cold regions on the basis of geography and summarize the research advances on the pathogenesis of migraine in cold regions to provide conceptual basis for the clinical diagnosis and treatment of this disease entity.

THE LABORATORY OF ICE CORE AND COLD REGIONS ENVIRONMENT

Affiliation unit: Lanzhou Institute of Glaciology and Cold Regions Environment, CAS Brief history: The Laboratory of Ice Core and Cold Regions Environment (LICCRE) was formally approved to open domestically and internationally by Chinese Academy of Sciences in April 1997. It is attached to the Lanzhou Institute of Glaciology and Geocryology, CAS.

Model test study of frost heaving pressures in tunnels excavated in fractured rock mass in cold regions

Based on the similarity theory, taking the horseshoe, city-gate and round linings as examples, the value and distribution regularities of normal frost heaving pressures （hereinafter as frost heaving pressures） in tunnels excavated in fractured rock mass in cold regions under different constraints and freezing depths were studied by a test model. It was found that the larger the frozen depth, the larger the frost heaving pressure, and the stronger the top constraint, the larger the frost heaving pressure. For the horseshoe lining and city-gate lining, the top constraint has a greater effect on the frost heaving pressures on the arch and the inverted arch. For the round lining, the influences of the top constraint on the frost heaving pressure in all linings are almost the same. The frost heaving pressure is maximum on the city-gate lining and minimal on the round lining. The largest frost heaving pressure all occur near the foot of the inverted arch for the three kinds of lining. Thus, the test data basically coincide with the observed in situ data.