Research on the calculation method of frost heave in the tunnel close-distance underpass the structure

WANG Lei

doi:10.19458/j.cnki.cn11-2456/td.2023.06.002

Abstract：Artificial ground freezing method is an important method for new tunnels to underpass through structure in soft and rich soil layer,among which the project of densely pasted frozen soil and structure is one of the most risky and difficult working conditions in freezing underpass project.Based on the newly built Line 18 of Shanghai rail transit passing through the operating Line 10 Guoquan Road subway station project,the ultimate tensile strain method is used to reverse calculate the frost heave and lifting deformation of the overlying structure during the densely pasted process,and the cal-culation formula of the frost heave displacement of the superstructure caused by the horizontal freezing densely pasted construction of subway tunnel is deduced.The deformation of the upper layer is regarded as the"structural"deformation with stiffness equal to that of the soil.The similar simula-tion experiment of freezing densely pasted is carried out,and the numerical value of the expansion co-efficient A of the front surface of the frozen wall in the grey silty clay in Shanghai area is 165.Several frost heave control methods such as sectional control freezing,staggered peak control freezing,soil removal and pressure relief are adopted in the project.The actual lifting displacement of the station floor in the construction process is 15 mm,and the frost heave of the station is calculated by the for-mula as 42.7 mm,and the lifting displacement value of the similar simulation test is 30 mm,and the calculated value of the formula is conservative.The research results provide data reference and theo-retical support for the construction of freezing close-distance underpass project.