Study on Long.docVIP

Study on Long-term Thermal Stability H7H0C ?of Air-cooled Subgrade /O0j/lm ? The permafrost area is about 25% of the land surface on the earth. In China, permafrost is about 22.4% of the country. As far as roadway in permafrost regions is concerned, the stability is determined by subgrade, the stability of subgrade is determined by permafrost, and the key problem to permafrost is thaw settlement. The effective solution to the key problem is to protect the underlying permafrost to avoid the thaw settlement of subgrade and ensure the long-term thermal stability of roadway by taking reasonable engineering measures in permafrost regions, which is one of the most important and complicated key technological problems in roadway engineering of permafrost regions. To avoid the influence of global climate warming on the thermal stability of permafrost roadway and prevent the roadway damages, based on the idea of proactively cooling foundation, the study on the two new subgrade structures, i.e. crushed-rock subgrade and duct-ventilated subgrade, must be carried out. Since their cooling effects on themselves and the underlying foundation soils are achieved by adjusting the convective heat transfer between air and subgrade, they are called the air-cooled subgrades. With the international latest problems in permafrost engineering, based on the Qinghai-Tibet Railway engineering, we conducted a series of programs on the cooling mechanisms and the long-term thermal stability of crushed-rock subgrade and duct-ventilated subgrade in permafrost regions. The research achievements are creative and important, namely, in theory, the cooling mechanisms of the air-cooled subgrades were discovered and the new calculational methods and mathematical models for the air-cooled subgrades were presented; in application, some effective solutions to the key scientific problems in important engineering of cold regions were proposed. The good effects were gained by applying them to the Qingh