退化性岛状冻土路基位移场地温响应研究

Study on Displacement Field Response of Patchy Subgrade along with the Ground Temperature in Degenerative Permafrost Regions

退化性岛状冻土连续性差,退融速率快,冻土路基病害较为严重。掌握该类路基随地温变化的变形规律,就可从根本上解决其热稳定性问题。为此,建立了该类冻土路基位移场的理论分析模型和有限元模型,并以实际工程为依托,通过对工后1 a内路基地温场、位移场的数值模拟及实测分析,提出了退化性岛状冻土路基位移场的周期性地温响应规律及"热缩"效应。研究结果表明:在一个周期内,该类冻土路基位移场的地温响应过程可分为冻胀、压缩及融沉3个阶段。其中冻胀与压缩阶段,地温变化对路基热稳定性影响较小,而融沉阶段产生的融沉位移对路基稳定性影响较大,且较地温变化有一定的滞后时间,当地温环境由升温状态向降温状态转变时发生,在此期间应加强对路基冻土的保护和监测。

The patchy subgrade has the poor continuity and faster retreat rate,the disease of subgrade is more serious in degenerative permafrost regions. Master the deformation law along with the ground temperature,the thermal stability problems of the patchy permafrost subgrade could be solved fundamentally. Therefore,this paper seted up a theoretical model and a finite element model,and based on practical project,it presented the periodic response law of the displacement field along with the ground temperature and the＂thermal-shrink＂effect by the numerical simulation and actual measurement analysis during one year after the project was done. The study results shows that the response process of displacement field can be divided into three stages： the frost heaving stage,the compression stage and the thawsettlement stage. In the first two stages,the influence is smaller for subgrade stability by changing the ground temperature,but the thaw-settlement displacement has greater influence during the last stage. The thaw-settlement displacement lags behind the ground temperature variation,and it happens as the ground temperature field passes from a rising to a lowering state,so we should strengthen the protection and the monitoring of patchy permafrost subgrade during this time.