Study On The Characteristics Of Frost Heave And Thawing Of Silty Clay Subgrade In Seasonal Frozen Area

Seasonal frozen ground area is widely distributed in China.The roadbed diseases caused by frost heave and thawing are emerging constantly.Roadbed diseases have a great impact on the use of road life and have a great impact on the economy of society.With the great idea of "One Belt And One Road" and the upcoming 2020 winter Olympic Games in Zhangjiakou,the country is bound to make great efforts in the construction of infrastructure and road transportation.Therefore,the influence of permafrost characteristics on road problems and the prevention and control measures have become one of the hot topics in current research.At present,a lot of achievements have been made in the theoretical research and prevention measures of permafrost regions in China.However,there are not many relevant research results in seasonal frozen areas and even fewer studies on subgrade in a specific seasonal frozen area.In this paper,the whole freezing-thawing process can be completely simulated on the basis of the size reduction test,and the superimposed effect of freezing-thawing process can better reflect the physical properties of soil during the freezing-thawing cycle.In order to study the frost heaving property of roadbed more accurately,the self-developed frost heaving equipment can meet the determination of temperature,moisture,frost heaving quantity and other indicators.The equipment considering the advantages and disadvantages of operation and function.The test results are accurate and reliable.Therefore,this paper aims at the roadbed of Zhangjiakou seasonal frozen soil area as the research object.And carries out the geotechnical test,laboratory model test and theoretical analysis method on the basis of field investigation and field test.The development law,influencing factors and internal mechanism of frost heaving,thawing and subsidence deformation were studied to provide theoretical basis for road construction in Zhangjiakou.The main research contents of this paper are as follows:(1)Carry out field investigation with the actual engineering highway as the drag,obtain the relevant parameters of soil material from the field soil test and indoor soil test,and prepare the configuration of indoor test material according to the relevant parameters.(2)Through reading a large number of domestic and foreign experimental literature on permafrost subgrade,the author has a preliminary understanding of theproperties of frost heave and thaw subsidence.And designed the soil freeze-heaving,thawing and subsidence test system,which takes temperature,moisture,load and water condition into consideration,It can simulate the whole process of freeze-thaw cycle of soil under natural water replenishment condition,And real-time record temperature and moisture changes,it can better study the characteristics of frost heave,thaw and subsidence of soil in seasonal frozen soil areas.(3)During the continuous freezing-thawing cycle,the influence of temperature at different cold ends on frost heaving under no load condition was studied.It includes temperature distribution,frost heaving amount,freezing depth,freezing rate and the influence of melting volume and melting coefficient.And the influence of different overburden conditions on the above research elements.(4)Finally,numerical simulation software is used to simulate the experimental results to verify the effectiveness of the model.