| The construction of Qinghai-Tibet Railway has proved that cooling foundation is the key technology ensuring the stability of embankment in permafrost regions, and heat pipe embankment can be applied to railway embankment in permafrost regions as an effective engineering structures. Research about heat pipe engineering structure in the regions has not been in any progress and research articles related to them has still rare appeared. Due to different geological conditions and permafrost environment on the application technical parameters of heat pipe and engineering effect, investigations on heat pipe during Qinghai-Tibet Railway construction can be referenced for the Chaidaer-Muli Railways, but More issues about heat pipe in the local railway should be combined with specific environmental conditions, and rational and scientific structure can be ensured, then long-term reliable technical support for operation can be provided.Climatic environment and permafrost conditions of Muli region are analysed in this paper, based on climate and permafrost temperature data during two years, through field test analysis and calculation, technology and embankment parameters of heat pipe are investigated. The cooling effect on embankment is studied, and the long-term cooling effect on embankment is discussed, then potential failure temperature field of filling embankment is discovered and at the same time response measures are proposed by numerical simulation. Innovative results obtained are as follows:(1) Freezing capacity and frost number in Chaidaer-Muli regionis is close to and even exceeded those in some areas along the Qinghai-Tibet Railway by analysing climate and permafrost temperature data in the region. Temperature of deep soil layer in winter season is higher than the climatic temperature in the permafrost regions. Heat pipe can operate well on the conditions.(2)A single heat pipe has a good cooling effect on surrounding permafrost, the total of accumulated negative temperature of over 1.0m soil layer below surface at embankment shoulder is much larger than the corresponding layer temperature below natural surface,and heat pipe play a cooling and cold storage role, by field test. (3) In the greatest thawing season, the same soil layer temperature of slope toe at heat pipe section is lower than the non-heat-pipe section, while cooling effect of heat pipe on embankment is not obvious. Shallow soil layer temperature of heat pipe embankment is lower than the respective natural soil layer temperature, while temperature of non-heat-pipe embankment is very close to and even higher than the natural temperature. That prove cooling effect.(4) The maximum deformation of 53mm of heat pipe embankment is more lower than 236mm of non-heat-pipe embankment by deformation monitoring and data analysis, and deformation amount of non-heat-pipe embankment has a greater fluctuation with the seasons, showing that heat pipe embankment has a better stability.(5) In conditions of the annual average climatic temperature of-5.3℃and global warming in the next 50 years, geothermal field characteristics of heat pipe and non-heat-pipe is analysed by numerical analysis, the results show that heat pipe has a good cooling effect on embankment, ground temperature is lowered obviously and the maximum thawing depth is uplifted by comparing temperature of left, right slope toe and center of heat pipe embankment with those of non-heat-pipe.(6) In conditions of the annual average temperature of-5.3℃and increasing of 0.052℃very year in the next 20 years, there will be an asymmetric distribution of thawbowl under 3m high embankment, which is main reason to produce vertical fracture. In the next 4 years, the elimination of thawbowl under embankment shows heat pipe can shorten existing time of thawbowl and reduce risk of thawing and fracture largely. |
PDF Full Text Request