Study On Frost Heave Law Of Stratum During Horizontal Freezing Construction Of Metro Twin-track Tunnel

Artificial ground freezing method has been widely used in metro tunnel engineering.Relative to other construction methods.The artificial ground freezing method has a large technical advantage.It can be applied to all kinds of complicated geological conditions.However,the frost heaving phenomenon of the formation during the construction of the subway tunnel freezing method has always been the focus of attention in the project.In this paper,the application status of artificial ground freezing method in Metro Tunnel Engineering and the research status of ground frost heave during the freezing period of metro tunnel are summarized.And the components and formation process of frozen soil,thermophysical parameters of frozen soil,mechanical properties,frost heaving mechanism and classification were described.This paper takes the horizontal freezing construction project of the subway double-track tunnel as the research object.Consider the net depth of three tunnels(6m,12m and 18m),the net spacing of six double-track tunnels(0.25D,1.0D,1.5D,2.0D,2.5D and 3.0D),and two freezing methods(simultaneous freezing and Freeze in order).Based on the orthotropic deformation characteristics of frozen soil,a thermo-mechanical coupling numerical simulation method is adopted.The ABAQUS finite element software was used to study the frost heave of the formation under different factors such as buried depth,clear spacing and freezing mode.The results show that,With the increase of the net spacing of the two-lane tunnel,the interaction between the two tunnels is getting smaller and smaller,and the maximum vertical frost heave displacement of the surface is getting smaller and smaller.As the depth of the tunnel increases,the maximum vertical frost heave displacement of the earth's surface decreases.The vertical frost heave displacement of double-track tunnel under simultaneous freezing mode is less than that of sequential freezing mode.Finally,this paper takes the horizontal freezing construction of the double-track tunnel of Felt Metro in Germany as the engineering background(the net distance of the double-track tunnel is 1.16M and the net buried depth is 8.5m).Similarly,ABAQUS finite element software was used to further study the frost heave law of strata under different freezing modes.The results show that the frozen wall reaches the design thickness after the two-lane tunnel freezes for 21 days,and the combined freeze measurement takes 42 days.Because of the different freezing time,compared with the simultaneous freezing mode,the ground frost heave displacement under the sequential freezing mode is slightly larger.The research results in this paper have certain reference value and significance for the design and construction of horizontal freezing engineering of double-track Metro tunnel.Figure 60 table 6 reference 78...