| In our country,about 55% of our country's land is seasonal frozen ground and 20% of our area is frozen throughout the year.With the development of transportation,China has built many tunnels in these frozen regions.However,these tunnels often suffer from freezing damage,such as cracking of the lining,cracking of the door wall,freezing of the drainage system,etc.The freezing damage is harmful to stability of the tunnel structure,it will also increase the cost of management and maintenance,and has bad effects on driving safety.In tunnel engineering,most door form are end wall and wing wall.Tunnel portal section is affected by external factors mostly.This article is based on indoor model tests,and using numerical analysis methods to study the temperature field,moisture field and frost heave deformation regular pattern of the tunnel entrance section of cold area.The relationship between the surrounding rock temperature,water environment and frost heave deformation is discussed preliminarily.The main works of this paper are as follows:(1)In order to provides basis physical parameter for model experiment and numerical analysis,some basic physical characteristic of soil are tested,including density test,moisture content test,direct shear test,liquid-plastic limit test and compaction test,to obtain some physical characteristics of soil,such as water content,density,shear strength index,liquid limit,plastic limit,etc.(2)According to the similarity theory,considering the effect of water-heat-force coupling research to determine the experimental similarity ratio of the model.Make a model,bury sensors,and collect and analyze the data of the temperature,lining deformation,force of the door wall and frost heave displacement of the tunnel entrance model.Experimental research shows:As the temperature decreases,the moisture in the model freezes and expands,generating frost heave force externally.The lower the temperature is,the greater the frost heave force and frost heave deformation are.When the model is completely frozen,the frost heave force and frost heave deformation gradually stabilize.After the model freezes,the lining produces horizontal deformation,the closer to the cave wall,the greater the amount of frost heave deformation;Frost heaving force produces a horizontal thrust on the tunnel door and wall;Under the three cycles of freezing and thawing,the freezing and heaving force of the door and wall is the largest when the second freezing and thawing is completed.(3)By establishing a water-heat-force coupling differential equation system,considering the non-linear factors of the latent heat of phase change and the process of water migration during the freezing process of the surrounding rock.And using the COMSOL Multiphysics software,the water-heat-force three-field coupling solution of the tunnel sectionis realized.The distribution of temperature field and water field and the characteristics of frost heave deformation of the tunnel entrance are discussed.(4)Numerical research analysis shows:Under numerical calculation conditions,during the freezing process,the water migrated to the temperature load surface;After the water in the model freezes,the soil body expands,and when there is a constraint,a frost heave force is generated.Among them,the top of the tunnel arch and the corner of the wall of the cave door are subject to the most frost heave force;Under the action of the horizontal frost heave force,the frost heave deformation occurred in the portal wall,and the maximum frost heave deformation in the horizontal direction is located on the top of the end wall and the wing wall. |
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