Critical Frost Heave Ratio of Shallow Buried Entrance Surrounding Rock of Tunnel in Severe Cold Region
The frost heaving effect in cold and severe cold regions affects the whole life cycle of tunnels.Focusing on the construction needs of a passenger dedicated line in a middle and high latitude region,the mechanical response of the lining structure under different frost heave rates of the rock and soil mass in the freezing and thawing region of the surrounding rock of the shallow buried tunnel is studied.The critical frost heave rate conditions are proposed,that is,(1)the maximum tensile stress of the lining structure ex-ceeds the standard value of the tensile strength of the material of lining structure;(2)The displacement of lining structure exceeds the specified displacement value.For the rock surrounding rock and soil surround-ing rock of the shallow buried entrance of the project,the critical frost heave rates are determined to be 2.00%and 3.10%respectively,and technical measures such as grouting to close the water conveyance channel of the freeze-thaw circle,setting up the blind drainage pipe,and laying the insulation board of the tunnel structure are adopted to ensure the safety of the tunnel entrance during the operation and mainte-nance period.
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