Study On The Deformation And Stability Of Highway Embankment In Permafrost Region Under The Condition Of Climate Warming

With the development of the western region and the implementation of the national "13th five-year plan" and "One Belt and One Road" strategy,we can foresee the construction of our transportation in the western region will usher in a new round of the peak in the next few years or even more than ten years.In the western mountainous area,there are lots of permafrost,among which the permafrost.distributed on Qinghai Tibet Plateau accounts for 80% of the total area of permafrost in China.Therefore,in the process of highway construction,it is inevitable to go through some permafrost regions due to the influence of linear indicators and other factors.At the same time,in the context of global warming,the extreme abrupt change of climate become more frequently,which has not been taken into account in the traditional highway design of the frozen soil area(Definition: the "climate warming" in the article title refers to "extreme climate change warming in the short term",which is called “climate warming” for short in the following article).The effect of the element on the subgrade exists in reality.Guided by two winter extreme abrupt change of climate events in permafrost regions of Norway and Sweden in 2007 and 2008,this paper was based on the study of the three field coupling models of heat-moisture-stress in the frozen soil and supported by the project of the Xinjiang G580 line and the field to Kang Xi tile highway field investigation.The research selected a typical slope section of the tundra and simulated the influence on the temperature field,moisture field,stress field,displacement field and the stability of subgrade by abrupt warming of 5°C,10°C and 15°C by COMSOL Multiphysics simulation software.Then the deformation and stability of the subgrade of permafrost subgrade under the condition of climate warming were obtained.Finally,some appropriate measures were put forward to protect the subgrade for excessive deformation,roadbed diseases and the stability of permafrost subgrade induced by climate warming.Research methods in this study contained field investigation,theoretical analysis,numerical simulation and the results were as follows:(1)The asymmetry of the lateral geometry of the roadbed on the slope of permafrost regions causes the asymmetry of the temperature field of the subgrade.The climate warming will cause the rapid decline of the 0°C isotherm on the subgrade of the permafrost subgrade.With the increase of the climate warming rate,the decline of the 0°C isotherm increased gradually.The response of the roadbed to the climate warming on the roadbed shoulders is more sensitive than the other points on the surface of the road.(2)The influence of climate warming on the water content variation of shallow soil subgrade in permafrost region is larger,and it has little influence on the deep soil moisture content variation in the subgrade.For the slope subgrade,the climate warming will result in the frozen soil melting into liquid water,infiltration under the effect of gravity,and accumulation at the end of the slope,which can cause the slope's mud over saturated and overflow easily.(3)Climate warming will cause rapid melting of frozen soil on the foot of slope subgrade,and the stress according to the difference of melting depth is very easy to cause the longitudinal cracking of the subgrade slope and the foot of the slope.(4)The deformation of permafrost subgrade is mainly composed of thawing deformation.The vertical thawing deformation of subgrade by the slope is higher than that on the side of the deviated slope due to the climate warming.When the climate warms up by 15°C,the longitudinal deformation difference of subgrade can reach 2.8cm,and the difference of lateral deformation reaches 1.7cm.It is easy to cause uneven settlement and longitudinal cracks.(5)The stability coefficient of permafrost slope subgrade in frozen state is higher than that of melting state.With the increase of temperature change warming,the stability of slope subgrade in permafrost decreases.When the climate warms up by 15°C,the stability coefficient of subgrade decreases from 2.49 to 1.59,with the decrease of 36%.We considered the factors(extreme climate change in the short term),that have been seldom studied before,in the study of the deformation and stability of highway subgrade in permafrost regions.The research results revealed the rule of deformation and stability of Highway Subgrade in permafrost regions under the condition of climate warming,which can not only offer new ideas for further study of permafrost in the future,but also provide some reference for highway design,construction and maintenance work in permafrost regions.