Study On Freezing Project Affected By Frost-Heaving And Thawing-Settlement Applied In Construction Of Subway Tunnel In The Coastal Regions

In recent years, artificial ground freezing has gradually developed into a freezing tunnel tunnel construction in coastal areas, especially the important one of the auxiliary methods. Although the level of artificial freezing method has many advantages, but the level of freezing the construction of many factors, the level of artificial freezing method, there are still some problems.Including the freezing of the process of frost heaving problems and the melting of settlement after thawing, and these may often lead to the displacement of the surface deformation. On the other hand there are many factors affecting the project, most of which locate in the urban areas, so the deformation of the surface displacement in any form will lead to serious consequences.This article first makes a theoretical analysis on the temperature field in frozenwall, then deduces the forming law of frozen wall.Secondly, by numerical simulation, analysis of surface frost heave in freezing process of displacement factors.In this paper, an equivalent load method representing frost heave load is put forward. Moreover, a method simulating the nonlinear deformation of unfrozen soil around frozen soil is proposed. Linear solution is adopted through stepped loading to approximate nonlinear solution. Influence of tunnel design parameters, building load and other related factors on frost heave surface displacement of the sensitive frost heave soil in coastal regions was systematically studied.The characteristic of thaw-collapse of artificial frozen soil is analyzed. A simplified method suitable for simulating settlement caused by defrost is put forward: a special constitutive model treating soil mass as a kind of material which is unable to endure tensile stress and its tensile property is entirely different from compressive property. Moreover, an equivalent load method representing thaw-collapse and increment method is adopted. The nonlinear effect that soil will become loose when it is exerted thaw-collapse load step by step is also considered. The qualified influence rules of design parameters of subway tunnel,building load and other related factors on thaw-collapse of the earth's surface after the frost wall unfreeze are studied systematically.According to the numerical simulation results on the basis of the corresponding measures proposed to reduce the displacement and deformation of surface frost heave and thaw displacement deformation.