Study On The Classification Method Of Tunnel Depth And Shallowness In Cold Area Considering The Influence Of Temperature Field

In tunnel design,the definition of depth and depth of tunnel is directly related to the accuracy of surrounding rock pressure calculation,which is also one of the important bases for selecting reasonable support measures and excavation schemes in tunnel design.It can be seen that the definition of deep and shallow burial is one of the core problems in tunnel design.And cold regions tunnel buried depth of significantly different with ordinary buried depth of the channel partition,so,this article mainly through the tunnel of indoor model test and numerical simulation of cold regions tunnel buried depth boundary buried deep in one of the main factors were studied emphatically,through changing the size of the tunnel buried depth of cold regions tunnel buried depth are discussed.Taking the loosening circle,ground subsidence,stress and displacement as the discriminant factors,the change rule of these factors is analyzed according to the change of buried depth.The main research contents and conclusions are as follows:(1)based on the similarity theory,the establishment of the tunnel model test,analysis of the change of temperature field,in the process of the experiment found that during warm,permafrost in the surrounding rock and tunnel surrounding rock near the surface are frozen,for shallow buried tunnel surrounding rock melt state or freeze + melting state,and deep buried tunnel is frozen + melt state;Due to the influence of atmospheric temperature,the freezing and thawing of tunnel surrounding rock and surface are constantly transformed into each other.Tunnel excavation will not only affect the redistribution of stress,but also make the temperature field and water field redistribute,so there are significant differences in the deformation failure mode and stress mechanism between the surrounding rock of tunnel in cold area and that of tunnel in non-cold area.Then using the modern non-contact measurement technology-digital photographic measurement software analysis and calculation,in the test process by changing the buried depth of the tunnel to study the depth of the cold area of the tunnel buried depth division,through the analysis of the cold area tunnel in different buried depth after the excavation of the failure mode and the formation of stable loose circle,Thus the boundary value of deep and shallow buried tunnel in cold region can be determined comprehensively.(2)The finite element software COMSOL was used to conduct the hydrothermal coupling of multiple physical fields,and the ground subsidence,displacement,stress and other data were analyzed in detail.The results show that the boundary value of depth and shallow burial obtained from the numerical simulation analysis is obtained,and the accuracy of the results is further verified by mutual verification with the model test.At the same time,the use of the existing common tunnel buried depth classified theory used in cold regions tunnel buried depth calculation,and the results were compared with the results of numerical simulation and model,to realize common tunnel buried depth of theory in the cold and the inadaptability of the tunnel,through the research,provide a reference basis for similar projects.(3)By using the finite element software COMSOL to carry out the water-thermal coupling action,the change rule of the temperature field and water field in the surrounding rock is analyzed,and it is concluded that under the influence of the temperature field and water field,the boundary of the buried depth of the permafrost tunnel is smaller than that of the general tunnel.