Innovative designs of permafrost roadbed for the Qinghai-Tibet Railway

Abstract

Under global warming scenarios, the passive method of simply increasing the thermal resistance by raising the embankment height and using insulating materials has been proven ineffective in warm and ice-rich permafrost areas and therefore could not be used in the Qinghai-Tibet Railway engineering. Instead, a proactive "cooled-roadbed" approach was developed and used to lower the ground temperature in order to maintain a perennially frozen subgrade. The concept that local and site-specific factors play an important role in the occurrence and disappearance of permafrost has helped us to devise a number of measures to cool down the roadbed. For example, we adjust and control heat transfer by using different embankment configurations and fill materials. The Qinghai-Tibet Railway project demonstrates that a series of proactive roadbed-cooling methods can be used to lower the temperature of permafrost beneath the embankment and to stabilize the roadbed. These methods include solar radiation control using shading boards, heat convection control using ventilation ducts, thermosyphons, air-cooled embankments, and heat conduction control using "thermal semi-conductor" materials, as well as combinations of above mentioned three control measures. This roadbed-cooling approach provides not only a solution for engineering construction in sensitive permafrost areas but also a countermeasure against possible global warming.warm permafrost, global warming, Qinghai-Tibet Railway, cooled roadbed

Thermal diodes, regulators, and switches: Physical mechanisms and potential applications

“…Heat pipe diodes are a relatively mature technology, and they have been developed for diverse applications ranging from temperature control of spacecraft sensors and electrical devices, 172 thermal energy storage, 173 nighttime radiative cooling, 174 and temperature control of buildings for reduced energy consumption. 175 In a large-scale infrastructure application, gravity-driven heat pipe thermal diodes known as thermosiphons were installed on the Trans-Alaska Pipeline System 176 and the Qinghai-Tibet Railway 177 to prevent permafrost melting. Many different heat pipe thermal diode designs with asymmetric shapes have been demonstrated (including the liquid trap diode, the liquid blockage diode, and the gas blockage diode), and these designs have been discussed in textbooks.…”

Changes to freshwater systems affecting Arctic infrastructure and natural resources

“…Mitigation techniques are routinely used to reduce the impact of hydrological processes on the geotechnical system. These techniques include water diversion systems to reduce flooding, slope and erosion protection measures and soil improvement techniques using geotextiles, and special foundation techniques including natural and/or artificial cooling of permafrost soils [ Cheng et al , ]. Design of water drainage systems associated with the road or railroad is important and necessary to ensure the structural integrity of the transportation system.…”

Climate Risk and Financial Institutions

“…Sources: Cheng et al 2008;Cheng 2005;UNEP 2007;Wu et al 2007;Miao 2009;Karl et al 2009;NRC 2008 Wear and tear on assets and infrastructure will increase due to climate change. Research in Alaska has estimated the additional impact of climate change on capital depreciation for the state's infrastructure by calculating the baseline replacement costs for public infrastructure based on documented life spans of various asset classes and standard financial techniques for calculating depreciation, and applying annual engineering depreciation rates for percentage changes in temperature and precipitation, based on asset class, topography, and proximity to floodplains.…”