Study On The Phenomenon Of Gradually Frozen Tunnel And The Caused Diseases Solutions To The Frozen Tunnel

The current design method of cold region tunnel is based on the frozen soil state before tunnel excavation.It is designed according to the seasonal frozen soil section,permafrost section and non-frozen soil section.It is considered that the boundary between the sections is basically unchanged,but the local permafrost tunnels and non-permafrost tunnels in the negative annual average temperature zone are running through the tunnels.Temperature will gradually decrease,and the surrounding rock of the non-frozen section will gradually freeze along the tunnel radial and longitudinal direction to produce new permafrost,which will cause the tunnel to gradually freeze and form a gradually frozen tunnel.The freeze-thaw state of surrounding rock is changed after the tunnel is gradually frozen.The original sectional design method is no longer applicable.It will lead to the failure of waterproof and drainage system,frost heave cracking of lining and other diseases.After decades of global warming,the gradual thawing of frozen soil will lead to the instability of surrounding rock and other diseases.Based on the general program of National Natural Science Foundation of China(51778475),this paper collects and sorts out a large number of data of tunnels built in the negative annual average temperature area,discusses the evolution mode of gradually frozen tunnels and analyzes the potential diseases of tunnels by means of statistical comparison,theoretical analysis,engineering data investigation and other research methods.Finally,revealing the phenomenon of gradually frozen tunnels solutions to the problems of lining structure,heat insulation and drainage system of the tunnel with gradual freezing.The main contents of this paper are as follows:1)Collecting and sorting out the data of temperature outside tunnel,ground temperature,temperature inside tunnel changing with longitudinal direction,interface temperature of surrounding rock and freeze-thaw change of surrounding rock in negative annual average temperature area,and study the relationship between them.Focus on the key temperature point of negative annual average temperature area,analyze the temperature inside tunnel in partial permafrost along transverse direction,and analyze the temperature inside tunnel in negative annual average temperature area.Longitudinal distribution law,study and reveal the phenomenon of gradually frozen tunnel and its evolution model.2)The design ideas and methods of anti-freezing,thermal insulation and drainage system for tunnel lining structure in negative annual average temperature zone are summarized.The potential diseases of lining structure,thermal insulation and drainage system under gradual freezing and thawing of tunnel are analyzed.3)Based on the phenomenon of freezing tunnel and its potential diseases,the paper studies the solutions of the diseases of the lining structure under the conditions of freezing and thawing.4)Based on the case study of Tianshan Shengli tunnel,the paper analyzes the existing problems and deficiencies in the current design,and puts forward the improvement scheme considering the gradual freezing effect.