THAWSTABILITY ASSESSMENT OF THE PERMAFROST FOUNDATION SOIL ALONG THE PROPOSED CHINARUSSIA CRUDE OIL PIPELINE FROM MOHE TO DAQING

The proposed ChinaRussia Crude Oil Pipeline runs through the permafrost area for about 500 km,across mountains,forests and wetlands with complicated frozenground engineering geological conditions. The maximum allowable thaw settlement of pipeline foundation soils is chosen as the assessment criterion. Using the meaning annual ground temperature and ice content of permafrost as the assessment indices,the permafrost along the pipeline route was classified into four types(according to10 and20℃): thermallystable permafrost and transitory cold permafrost,thawunstable warm permafrost（-10～-20℃）and extremely unstable warm permafrost（-10℃）. The recommended construction modes include conventional burial,insulated burial,drainage control,refill with nonfrostsusceptilble and/or thawstable soils,elevation,and even above ground bent/dike with or without drainage control. Using this assessment system,about 430km of permafrost of the pipeline route has been evaluated in detail. The assessment system is simple in criteria,and has resulted in appropriate and practical products. 