Study On Permafrost And Its Influence On Highway Engineering From Boundary To Ritu Section Of 219 National Road In Ali Area Of Tibet

219 National Road,also known as the Xinjiang-Tibet highway,is an important strategic road for China.It is the only channel connecting Xinjiang and Tibet at the present stage,and also an important road for material transportation in Ali region of Tibet.In this paper,the section is the object of study,which from boundary to Ritu of National Road By collecting and sorting out relevant data,and adopting comprehensive exploration method,the paper investigates the permafrost along the line,finds out the development characteristics of permafrost and the distribution of bad geology and road diseases,evaluates the engineering geological conditions of the permafrost section,and puts forward corresponding engineering measures.The study section north to K649+200,south to K926+480.135.Thereinto,section K649+200 to K773+450 distributed continuous sheet permafrost,and section K773+450 to K930+000 distributed seasonally frozen ground.The permafrost in this region is classified as less ice permafrost? more ice permafrost ?ice rich permafrost?full frozen permafrost?soil-bearing ice,while soil-bearing ice rarely appear?The annual mean ground temperature of permafrost is 2.0 ? ~ 3.5 ? in this area,belongs to the low temperature permafrost.In general,the permafrost has less ice from the north to south.The permafrost are mostly multi-ice or rich frozen soils from K649+200 to K758+750,and mostly less ice and more ice permafrost from K760+000 to K773+450.The natural upper limit of permafrost is between 1.5 and 2.5 meters.Road diseases caused by permafrost mainly include frost heave,melt and submerge,and pulping.Thereinto,these sections have serious frost heaving,thawing and sinking phenomenon that the roads development the permafrost layer with the fine granular soil.These sections are more heavily pellucid and include K871+200~K872+800?K874+200~K874+600?K891+900~K892+600.Other road diseases include snow damage,water damage,etc.Generally speaking,the engineering geological conditions of the whole line are general,such as the Hongshan lake section,the Longmucuo lake section and the Duomaqu valley sections.While,the engineering geological condition of the Quanshui lake section ?the Songxi grassland section and the Hongtudaban mountain section are poor.Finally,based on the investigation of permafrost and the development of road diseases along the line,the specific and targeted suggestions on remedial measures were put forward.