Nonlinear Thermal Analysis for Qing-Tibet Railway Embankments in Cold Regions

Heat convection in ballast mass in railway embankments is a problem of heat convection in porous media. In order to calculate the temperature distribution of the Qing-Tibet railway embankment from the governing equations used to study forced convection for incompressible fluids porous media, detailed finite-element formulas for heat convection in porous media are derived using Galerkin’s method. The temperature distributions on central lines of the traditional railway embankment, the ripped-rock embankment, and the ripped-rock revetment embankment that were constructed on July 15, 2002 have been analyzed and compared on July 15, October 15 in the 24th year after construction, and January 15 in the 25th year after construction under the climatic and geological conditions on the Qing-Tibet Railway. The calculated results indicate that the traditional railway embankment will raise the permafrost temperature under the embankment base and make the permafrost embankment thermally unstable. The ripped-rock embankment and the ripped-rock revetment embankment will reduce the permafrost temperature under the embankment base in cold regions, therefore maintaining the thermal stability of permafrost. However, the ripped-rock embankment needs more rock mass while the ripped-rock revetment embankment need less rock mass, and its construction cost is lower than that of the former. Therefore, it is highly recommended that the ripped-rock revetment embankment be used for the Qing-Tibet railway embankment structure in high temperature permafrost regions so that the permafrost embankment can be protected as much as possible.     

Experimental Study on the Ventiduct Embankment in Permafrost Regions of the Qinghai-Tibet Railroad

This technical note presents an experimental study on the ventiduct embankment in permafrost regions of the Qinghai-Tibet Railroad. Two experiments were conducted in a test box and they were designed with similarity theory. Some preliminary results are given to describe the temperature regime properties of the embankment, and the temperature differences between the ventiduct embankment and the normal embankment are compared. Results showed that the ventiduct embankment has a good cooling effect; it has a faster cooling rate than the normal embankment; the range of influence of a single duct can reach one duct diameter; the temperature distribution of the ventiduct embankment is asymmetric along the wind direction.     

Three-Dimensional Nonlinear Analysis for the Cooling Characteristics of Crushed-Rock Interlayer Embankment with Ventilated Duct along the Qinghai-Tibet Expressway in Permafrost Regions

The crushed-rock embankment and duct-ventilated embankment have been used as effective cooling measures to protect permafrost underlying the Qinghai-Tibet Railway from thawing in China. These two cooling techniques are not directly applied to the Qinghai-Tibet Expressway, however, due to the large width and higher temperature of pavement surface. Therefore, considering the heat transfer characteristics of crushed-rock interlayer embankments and duct-ventilated embankments, we designed the crushed-rock interlayer embankment with ventilated duct. For cold regions engineering projects, the thermal regime is the most important factor that determines the stability of construction. To investigate the thermal stability of this new type of embankment, a three-dimensional numerical model was developed based on heat and mass transfer theory. The model includes coupled heat transfer between the airflow and the duct wall, air convective heat transfer within the crushed-rock interlayer, and heat conduction with phase change in the soil layer. The computational results indicated that the numerical model can reasonably solve the coupled heat and mass transfer for the crushed-rock interlayer embankment with ventilated duct. Based on an assumption that the mean annual air temperature will increase by 2.6°C in the next 50years, it was determined that in areas where the mean annual air temperature is currently ?4.0°C, the crushed-rock interlayer embankment with ventilated duct can be an effective measure to decrease the underlying ground temperature and ensure the stability of the Qinghai-Tibet Expressway in permafrost regions.     

Nonlinear Analyses for Coupled Problem of Temperature and Seepage Fields in Cold Regions Retaining Walls

In this paper, a mathematical mechanical model and the governing differential equations of the coupled problem of temperature and seepage fields, with phase change, are derived from the theories of heat transfer and seepage. The finite-element formulation of this problem is then obtained using Galerkin’s method. Lastly, an illustrative example is provided. The example shows that the effect of seepage field on the temperature field of cold region retaining walls is large. The effect of this factor on cold region retaining walls should be taken into account in cold regions engineering design. Comparisons of the results of this approach with the measured data in the field have been made. The agreement is very good.     

Identifying Critical Sources of Bridge Deterioration in Cold Regions through the Constructed Bridges in North Dakota

This paper presents the performance of constructed bridges in cold regions through examining the bridges in North Dakota that is one of the coldest regions in the United States. Unique approach of a combined multiple regression and geographic information system technology is employed to evaluate the performance and to identify the critical sources affecting deterioration of the 5,289 bridges sampled from the National Bridge Inventory database inspected between 2006 and 2007. Typical parameters examined include physical, material, and environmental factors associated with the existing bridges. The importance of maintenance and repair is highlighted. Traffic volume significantly influences the level of deterioration of the bridge decks. Year built is the most significant contribution to the structural deficiency of the bridges, followed by structural characteristics and traffic volumes. The presence of water particularly influences the deterioration. Concrete bridges are more durable than steel bridges. Truss systems may not be recommended for cold regions.     

Modeling Impacts of Thaw Lakes to Ground Thermal Regime in Northern Alaska

In northern Alaska, the ground is largely underlain by permafrost. Many engineering problems in this region can be attributed to the variations of ground thermal regime. Engineering projects such as construction of gas pipelines must be based on a good understanding of ground thermal regime and its interaction with seasonal climate changes. Numerical modeling is used to simulate a multimedia system with transient heat transfer in this research. The system includes a snow cover on the top, a shallow lake in the middle, and soils beneath the lake. The finite-element method is used for the spatial domain solution, and the finite-difference method is used for the temporal domain solution. The model is applied to three sites in northern Alaska for a nine-month period during the winter of 1995–1996. The result reveals the impacts of thaw lake on the ground thermal regime, the formation of the talik, as well as the formation of ice in the lake. The model is verified against field observations. The difference between the simulated and observed ice thickness is less than 3%.     

Case Study of Degrading Permafrost beneath a Road Embankment

This paper reports on a case study of degrading permafrost beneath a road embankment in Northern Manitoba, Canada. Field measurements of ground temperatures for a three-year monitoring period have been used in calibrating the geothermal model developed to reproduce the conditions and trends in the subsurface thermal regime beneath the embankment. The numerical model was used to investigate the future ground thermal regime of the foundation and evaluate the potential impacts of embankment construction and climate change. Particular interest was paid to the foundation soil near the toe of embankment where relatively rapid permafrost degradation was occurring.     

Performance of Polymer Modified Asphalt Bridge Expansion Joints in Low-Temperature Regions

Conventional asphalt bridge expansion joints used in low-temperature regions generally show cracking within the first 2?years. To improve the low-temperature performance of these joints, the commercial MEIJIA asphalt binder commonly used in bridge expansion joint construction was modified with two polymers: thermoplastic rubber and rubber. The goal is to find an optimum combination of polymers, binders, and aggregates to improve the performance of asphalt expansion joints in low-temperature regions. The polymer modified binders and mixtures were evaluated for their low-temperature properties using ductility, penetration, indirect tension, and bending tests. The study indicates that performance of these joints at low temperature can be enhanced significantly with the right combinations of polymers, binders, and aggregates. Four expansion joints made with the polymer modified asphalt mixtures were installed on two bridges in a cold region. A construction procedure was also developed to install these joints properly to minimize low-temperature cracking along the interface between the joint and bridge deck. After 7?years of service, the four joints show good performance without any visible cracking or rutting.     

Influence of Subsurface Drainage on Soil Temperature in a Cold Climate

Soil temperature during springtime is an important factor for crop establishment and growth in poorly drained soils of northwest Minnesota. In this region, shallow water tables causing spring planting delays and excess water conditions during the growing season, may have contributed to significant unplanted cropland and yield reductions in recent years. Temperature is a regulating factor for many biological and chemical processes in the soil. One of the most commonly cited benefits of subsurface drainage on poorly drained soils is faster soil warm-up in the spring. Previous studies of this phenomenon do not provide definitive conclusions concerning the influence of soil drainage on soil temperature. The results of three site years of field observations of soil temperatures from drainage research plots at two locations in northwest Minnesota are presented herein. Replicated soil temperature and water table depths were measured continuously at five depths for two drain spacings and an undrained treatment. Subsurface drainage was found to significantly increase soil temperatures in both a coarser textured Vallers loam soil and a finer textured Hegne silty clay loam soil. Up to 4°C temperature increases occurred primarily between May and July with the greatest increases at 30–60?cm depths. Treatments with narrow drainage spacing showed a greater spring temperature increase than treatments with wider drainage spacings.     

议少数民族地区图书馆联盟的建设

文章介绍了国内外图书馆联盟发展的现状,探讨了我国少数民族地区图书馆联盟建立的必要性,可行性,指出了建立少数民族地区图书馆联盟需要注意的问题.     

In Situ Test on Cooling Effectiveness of Air Convection Embankment with Crushed Rock Slope Protection in Permafrost Regions

An experimental air convection embankment (ACE) was constructed in Beiluhe on the Qinghai-Tibet Plateau during 2001–2003, using coarse (5–8 and 40–50 cm), poorly graded crushed rock fill material on the slope of embankment with thick ground ice permafrost foundation, which should be called the air convection embankment with crushed rock slope protection (ACE–CRSP). The highly permeable ACE–CRSP installation was designed to test the cooling effectiveness of ACE–CRSP concept in an actual railway project. Ground temperature data were collected from test sections on the railway with thermistor sensor strings. The results showed that the mean ground temperature under the layer of the crushed rock with coarse particle diameter of 40–50 cm was lower than that under one with finer particle diameter of 5–8 cm, and the fluctuating range of temperature under the former was bigger than that under the latter. It was obvious that the maximum thaw depth was raised under the layer of crushed rock with coarse particle diameter of 40–50 cm, which resulted from the stronger cooling effectiveness of air convection during the winter. The amount of heat exchange also showed that the absorbed cooling energy of the foundation, under the layer of the crushed rock with coarse diameter, was larger than that with finer diameter.So, we believe that the cooling effectiveness of the crushed rock layer with coarse diameter was stronger than that one with finer diameter.     

Seasonal Thermal Displacements of Gravity Dams Located in Northern Regions

Seasonal temperature displacements are an important component of the total displacements recorded by pendulum measurements at gravity dams located in northern regions. A hybrid dam displacement model is presented in this paper to interpret these displacements and extrapolate the response for an extreme thermal event not yet experienced by the dam. The hybrid model uses a simplified deterministic structural dam representation with beam elements in complement to a hydrostatic seasonal time (HST) statistical displacement model. Comparisons are first established between 1D heat transfer analyses of typical gravity dam sections, and 2D finite-element (FE) analyses. Thermomechanical displacements are compared to show the validity of the proposed simplified deterministic beam model for typical dams. A case study of an actual 40?m gravity dam located in Quebec, Canada is then presented. It is shown that the deterministic model can be calibrated using the pendulum displacements and the HST model. The calibrated deterministic model is then used to extrapolate the displacement response for extreme thermal events not yet experienced by the dam. The proposed methodology represents a simple extension of the gravity method, widely used to verify gravity dam stability, as a first step to interpret recorded pendulum displacements and set appropriate warning and alarm levels on a rational basis before developing 2D and 3D thermomechanical FE deterministic dam models that require a lot of resources and expertise to be used effectively.     

Field Study of Concrete Maturity Methodology in Cold Weather

The objective of this study was to assess the reliability and potential benefits of using the concrete maturity method in cold weather. This paper reviews the concrete maturity method, describes the technology and field observations, and discusses potential benefits of using concrete maturity in cold climates. The concrete maturity method is based on the idea that concrete strength development is strongly correlated with the curing temperature history. Modern sensor and processing devices (loggers) are able to measure and record the temperature of concrete over time. This information could be used to predict concrete strength over time. Findings from a case study in application of the maturity method in an industrial construction project in Edmonton, Alta., Canada indicated a significant potential time and cost reduction. The study also indicated that the concrete maturity methodology enables reliable quality control through the accurate estimation of in-place concrete strength. The real time information available through the concrete maturity method allowed the project manager to be proactive in managing heating and protection to ensure that the proper level of concrete strength was developed.     

冷轧镀锌线退火炉控制系统

介绍了冷轧镀锌线无氧水平退火炉自动控制系统的功能及其为提高镀锌板质量发挥的重要作用。     

冷轧带钢连续退火模拟实验机的研究与控制系统的开发

 成功研制出一种冷轧带钢连续退火模拟实验机,应用SIEMENS SIMATIC S7系列PLC作为基础自动化控制系统,并用Step7软件编写控制程序,可满足高精确度信号测量和高精度温度控制等功能,控制和测量精度达到目前国外同类设备的水平。该模拟实验机可模拟带张力试样在不同保护气氛下的退火生产过程。阐述了该实验机的功能、设备结构、控制系统的开发和主要性能指标。     

抓住西部大开发机遇加快云南有色金属工业发展

简述了西部大开发的意义，方针，重点和政策，从资源，产业，技术和改革成果分析了云南有色金属工业的比较优势，并就以结构调整为主线的发展思路进行了探讨。     

土壤离子电导率法和地电提取法在青藏高原冻土区寻找隐伏金矿的对比研究

青藏高原冻土区找寻隐伏矿床的难度很大,选用传统的物化探技术手段并未取得找矿突破。本次研究采用土壤离子电导率和地电提取测量法在高寒区--扎家同哪金矿区开展隐伏矿找矿预测工作,在未知区圈定了3处找矿远景靶区,其中,Ⅰ类找矿靶区异常规模较大,位于测区中部,成矿条件好,应作为下一步工作的重点勘探区。此外,选择研究区4号勘探线作为已知剖面,开展了方法有效性和可行性试验研究,结果显示,已知矿体上方有明显的土壤离子电导率异常地电提取Au元素异常,进一步证实这2种方法组合在青藏高原冻土区的找矿应用效果显著,值得推广应用。     

Microcosm Approach to Study Transport of Polychlorinated Biphenyls in Sediment

The transport of polychlorinated biphenyls (PCBs) in sediment is difficult to study in the laboratory due to their low solubility and strong tendency to sorb to sediment and experimental equipment. A small-scale laboratory microcosm was designed to study PCB transport in anaerobic surface sediment at microscale and to quantify transport rates. Results of verification testing showed that the experimental system enabled quantitative characterization of the diffusive transport of PCBs in sediment in a reasonable time frame (months). The fine-spatial-resolution results obtained were as expected with the less chlorinated, more mobile congeners transporting the fastest and the more heavily chlorinated compounds transporting more slowly. This laboratory microcosm system could be used to study the transport of many types of pollutants in sediment, but is particularly useful for hydrophobic organic compounds.     

Effects of Clay Content and Temperature on Crude Oil (Nonvolatile Components) Transport in Unsaturated Soils: Centrifuge Study

Surface soil contamination due to oil spill is one of the major environmental concerns. The extent of the contaminated depth governs the design and installation of remediation method and monitoring system. Physical modeling of oil contaminant in unsaturated soils was conducted using a centrifuge. Preliminary results on effects of clay content and temperature on the contaminant profile near the surface are presented. The experimental results indicate that centrifuge modeling may be a viable method to study the problem of immiscible oil movement in partially water-saturated soils.     

数字化脉冲燃烧控制技术在冷轧带钢连续退火炉上的应用

介绍了数字化脉冲燃烧控制的原理,重点说明了脉冲燃烧控制在冷轧带钢连续退火炉上温度控制的方法,通过实例表明了脉冲燃烧控制炉温精度高、节能性好、动态响应性强等优点,指出数字化脉冲燃烧控制是燃烧控制技术未来发展方向。同时也总结了脉冲燃烧控制在使用过程中的问题和局限。