Study On The Artificial Freezing Effect Of Cross-passage Under Seepage Field

In recent years,with the rapid development of urban subway construction in China,the number of contact channel projects has gradually increased,and various engineering accidents have occurred.The influence of groundwater flow on freezing effect is one of the main causes of accidents.To this end,this paper takes an interval contact passage constructed by freezing method in Guangzhou Metro as the research object,and adopts the method of combining model test and numerical calculation to study the flow-thermal coupling problem of the contact passage under the condition of special hole arrangement,and obtains the following main conclusions :(1)Under the action of seepage,the freezing wall intersection time of the contact channel will be greatly prolonged,and the freezing wall of the upstream and downstream side walls will show obvious heterogeneity.Moreover,with the increase of flow velocity,the heterogeneity of the freezing wall will further expand.When the flow velocity reaches a certain critical value,the freezing wall will no longer intersect.(2)Under the seepage condition,the difficult problem of the freezing wall circle of the contact channel mainly occurs in the side wall area facing the water surface.Since the contact channel is generally arranged in the way of ‘upper narrow and lower wide’,the freezing wall of the side wall shows a trend of gradual circle from top to bottom.(3)Based on the model test data,the regression analysis method is used to establish the function relationship between seepage velocity,hole spacing and frozen wall thickness,whi ch provides a reference for similar engineering design.(4)The optimization method of adding auxiliary freezing hole and facing water freezing hole is put forward,and the numerical calculation method is used to compare the advantages and disadvantages.The results show that the auxiliary freezing pipe method is suitable for projects with small flow velocity and strict frost heave deformation requirements,and the waterward freezing pipe method is suitable for projects with large flow velocity and relativel y loose frost heave control.