Study Of Early Warning On Raodbed Diseases Of Qinghai-Tibet Highway In Permafrost Regions

With the development of the global warming and human activities, the environmental conditions along the Qinghai-Tibet Highway in permafrost regions are disturbed and appear new changes. As a result, some new diseases of the roadbed occurred and the former diseases developed under the changes of the engineering geological conditions. In order to inspect the influences of the changes on roadbed stability, a study of early warning on roadbed diseases was taken and establishment of corresponding long-term monitoring system was described.In this paper, based on diseases investigation and research on the Qinghai-Tibet Highway in permafrost regions for many years, the evaluation index for frozen soil roadbed is put forward, and roadbed diseases of the highway in the permafrost regions were evaluate. Based on analysis of the characteristics of the diseases and the distribution law of thermal regimes of the roadbed under the condition of the global wanning, the cause of diseases and their developing law was revealed. And also, the relationships between disease ratio and the ground temperature, ground-ice content, the embankment height and the serving time of the roadbed were analyzed. It was found that the roadbed diseases are mainly subsiding deformation, showing as melting subsidence in low-height roadbed and unsymmetrical longitudinal cracks in high-height roadbed.Based on a systematic summary of the characteristics of the fuzzy logic theory and the roadbed diseases of Qinghai-Tibet Highway in the permafrost regions, the fuzzy math theory was adopted in construction of the early warning.In the warning system, some key factors, including the mean annual ground temperature, frozen soil type(ice content), drainage condition of the roadbed and the method of special adjustment were selected among the summarized 21 factors, which were classified into 5 categories. Then linguistic variables and fuzzy subjection function for describing the diseases and their intensity were installed. At last, 37 items of the logic rules for describing influencing factors of the diseases and their relationship with the disease intensity were put forward, combining the disease investigations and experience from experts. To use the 7 items of the logic rules, Matlab Fuzzy Logic Toolbox was adopted for inputting the factors of the mean annual ground temperature, frozen soil type(ice content), drainage condition of the roadbed and the method of special adjustment as the key factors. From deductive reasoning, output indexes of the certain serving time and the roadbed condition can be obtained.