| With the increase of human production activities in permafrost regions,the requirements for power transmission are increasing day by day.However,during the later stage use of the transmission towers in the permafrost region,due to the cyclical change of the external environment temperature,the pile foundation suffered frost heave and thaw.When the pile foundation freezes and expands in winter,The rising displacement of the pile is almost the same as the frost heaving value of the nearby soil,and when the soil body thawed,the pile was buried deep in the frozen soil.In the permafrost layer,the thawing value of the pile is smaller than that of the soil,resulting in a relatively poor deformation of the pile and soil.Such reciprocating action will lead to "upfreezing" disease,which will seriously affect the safety and usability of the transmission tower.In order to obtain the long-term effect of the hot pile foundation on the treatment of the disease,this paper uses the thermal pole foundation of the power pole tower and the ordinary pile foundation of the Wangbu section of the Qinghai-Tibet Railway under the background of the temperature rise of 2.6? in the next 50 years.Based on the field test of the non-heated rod pile foundation,using the ANSYS numerical simulation software to carry out a long-term stability study on the presence or absence of the thermal rod pile foundation through the thermal-mechanical coupling method,it is concluded that:(1)As the temperature of the external environment increases year by year,the temperature of the soil in the range of 8m deep in the frozen soil generally shows an upward trend.With the increase of the period of time,the thickness of the active layer of the non-thermal rod pile foundation has increased,which seriously affects the stability of the pile foundation.The hot rod pile foundation has a good cooling effect on the temperature of the soil around the pile with a soil depth of 3m to 8m.The maximum temperature drop at a depth of 5m is 2.6 ?,and the hot rod can increase the upper limit of frozen soil.Maintain the stability of frozen soil.However,with the increase of years,the effective working efficiency of the hot rod is gradually declining,which leads to the weakening of the cooling effect on the soil layer.(2)Under the same external temperature load,the hot rod will greatly increase the cooling rate of the frozen soil.The excessive cooling rate will make the moisture inside the soil have completed the freezing process before the migration of the soil.The frost heaving of the soil has an inhibitory effect.(3)When the frost heave of the pile foundation occurs in winter,the frost heave values of the pile body and the nearby soil are almost the same(without considering that the pilebody is pulled off).The thermal pile foundation has a lower temperature effect than the ordinary pile foundation due to the cooling effect of the hot rod.The value is reduced,and the temperature of the soil layer is lowered by the hot rod in winter as a whole,so that the temperature of the soil body is still lower than that of the ordinary pile foundation in summer,so it also has a good inhibitory effect on the melting of the soil body.(4)Through the analysis of the 20-year mid-year freeze-pull value of the hot pile foundation and the common pile foundation: the average annual freeze-pulling value of the common pile foundation is about 19 mm,the average annual freeze-pulling value of the hot pile foundation is about 10 mm.It can be concluded that the hot rod pile foundation has a good effect on the treatment of the frozen pull disease of the transmission pole tower pile foundation in permafrost regions. |
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