Zonation and assessment of engineering geology for frozen-ground environments and conditions along the proposed China-Russia Crude Oil Pipeline route

The zonation principle and criteria of engineering geology for frozen-ground conditions along the proposed China-Russia Crude Oil Pipeline route(Mohe-Wu’erqi) were determined on the basis of careful,systematic analyses of large amount of survey data of frozen-ground conditions,and features of pipeline engineering foundations impacted by frozen ground and the interactive nature between the pipeline and freeze-thaw processes of the ambient foundation soils were considered.Two zones of frozen ground conditions,permafrost and seasonally frozen ground,were divided according to the regional distribution of various types of frozen ground and the frozen ground conditions for environmental engineering geology.Four subzones of permafrost were further divided according to the areal extent of permafrost with consideration of permafrost temperatures and thickness,and vegetative coverage.151 segments of frozen ground types were distinguished from the four subzones according to the ice/moisture contents of permafrost with consideration of frost heaving and thaw settlement potentials of soil layers.Assessment was made in the order of zone,subzone,and segment.The 151 segments were grouped into four types of engineering geology sections: good,fair,poor,and very poor.This zonation and assessment system was proposed for and adopted in the design,construction and operation,and environmental protection of the proposed China-Russia Crude Oil Pipeline.It was proven effective in providing a scientific evaluation of frozen-ground conditions in rugged terrains in the Da Xing’anling Mountains.