The Study On The Typic Geological Hazards At Permafrost Areas In The Center Of Qinghai-Tibet Plateau

On the global warming condition, disaster research on the frozen ground is one important task of Quaternary geologic hazard research. There are 150km2 permafrost area in Qinghai-Tibet Plateau. Frozen and melting occurs in turn and so the damage to engineering and ecotope is serious. The damage of Qinghai-Tibet is up to 31.7%. It has important actual significance to study on the geological disaster of the frozen ground in the center of Qinghai-Tibet Plateau.After field geologic survey and collection of disaster data in study area, based on topographic zoning, geology,hydrology,topography,structure present status and frozen ground existing condition data are integrated to study the distribution of hazards. Ten disaster types are defined. The generation mechanism of geologic disaster in frozen ground is analysed and the evolution model is built.The author thinks that in the center of Qinghai-Tibet Plateau, frost heaving and thaw collapse are major hazard roles; water content and coefficients of frost heaving and thaw collapse are important factors in the degree of development of hazards, and Tertiary Wudaoliang formation and Yaxicuo formation lacustrine sediment is the main strata to cause disaster.The paper analysed the regionality of hazards phenomena and the characteristics of frozen earth in permafrost area, hazards grade was built and the study area were divided into 13 zones(except desertification zone).The average to good disaster zones are all located in setting basin, river valley and foothill area in the north of Tanggula Mountain. According to the analysis of three types-11 factors related to the genesis of hazards, the hazardous synthetic evaluation of all kinds of geologic disasters in frozen ground was estimated. The study area were divided into 26 disaster dangerous zones.Based on the satellite data of nineteen seventies and nineteen nineties, topography and geology data, the trend in development and present status of desertification in the past 30 years of the work area was studied. Four desertification smear zones were divided and six desertification warning areas were identified. The desertification evolutionary process of typical desertification area was analysed. It is concluded that permafrost degradation leads to the desertification expansion to the south and north from the center. The windblown desertification to the south is intensified and the advance speed is about one latitude degree per 20 years.From the south of Tanggula mountain to the north band of Cuona Lake is the serious windblown desertification area. It makes a big damage to the ecotope and Qinghai-Tibet railway in the south of Qinghai-Tibet Plateau.The application of the outcome and data of frozen earth in response to temperature variation model can predict the variable trend of hazards in next 50 years. The next fifty years were predicted to be a active period of the disasters occurrence in Qinghai-Tibet Plateau, setting basin, river valley and plateau surface to the north of Tanggula mountain were the key disaster areas, moreover, the hazards of thaw collapse are serious. The harnessing of frost heaving and thaw collapse is predominated by the way of waterproofing and draining through engineering, and roads and railways are predominated by bridging, building culverts, and blocking up roadbed, and filling earth excavation is fit for serious hazards in local unprotected permafrost area.