Study On Stability For Low Embankment Of Qinghai-Tibet Railway In Tanggula Mountain Permafrost Area

In order to satisfy requirements of design of longitudinal degree of slope and the joints of different structures,low-roadbed which is lower than critical height was applied in permafrost roadbed constructions in Tanggulashan Mount sector of Qinghai-Tibet railway.The height of embankment is lower than 4m due to the confinements of thickness of rubble and filling when the measure of ballast ventilation is applied.It is some special performances in thermal and engineering stability for above two different low embankments because of the influences of climatic conditions and hydro-thermal environment.Based on analysis of regional environment and permafrost conditions of Tanggulashan Mount region and the survey of test construction and the long-period forecasting,engineering stability of low-roadbed was researched profoundly and systematically in this paper.Effect of protection for substratum permafrost from low embankment is analyzed through studying on the field information about freezing and thawing process in Tanggulashan Mount area.Based on the test data,the tendency of ground temperature is simulated in the theory derivation on the condition of gradual rising temperature and complexity of hydro-thermal environment.After theory derivation and field investigation several lower embankments in different multi-conditionsThe conclusions are as followed:1.In low temperature permafrost region where environmental atmospheric temperature is lower than -5.6℃,low-roadbed construction can protect permafrost effectively in a relative long period.But its effect will be weakened annually when atmospheric temperature is increasing annually,so preventive strengthening measures must be taken.2.when environmental temperature is relative high(about -4℃),the protection effect of low-roadbed construction to permafrost is not obvious,no matter in low temperature permafrost region or in high temperature permafrost region.It must be strengthened.It is effective to apply some preventive strengthening measures such as using soil berm and thermal rods at toe or using foliated rock berm and thermal rods.It is testified by the railway construction and initial operation. ##本文无英文摘要内容...