Analysis On The Influence Of Cross Passage Ground-Freezing Construction On Segment Tunnel Lining

In recent years,with the extensive development and utilization of underground space,the national subway construction has entered a period of rapid development.As a disaster prevention and rapid evacuation facility under the emergency condition of the subway tunnel,the cross passage has become a necessary supporting facility for the subway tunnel.At present,mine tunnelling method is mainly used in the construction of cross passage.However,mine tunnelling method has corresponding limitations in weak and water-rich stratum,and accidents such as surrounding rock collapse and water inrush easily bring great risks to the construction safety.Therefore,it is necessary to cooperate with the ground-freezing method grouting method and other auxiliary methods to improve the construction conditions.The ground-freezing method has been widely used in the construction of cross passage because of its advantages of effectively isolating groundwater,improving the strength of surrounding rock in water-rich layer,flexibility and no pollution.However,the ground-freezing method may also cause problems such as frost heaving and surface uplift during method,melting and subsidence during thawing,which may threaten the safety of engineering structure.This paper relies on the construction of a subway cross passage in a city to monitor the temperature,stress and deformation during thawing,and establish a threedimensional finite element model to distinguish the three soil states of undisturbed soil,frozen soil and thawed soil according to the unit temperature simulate the frost heave and thaw settlement of soil.At the same time,a transient analysis of the temperature change process and thermal stress during the thawing period is carried out,focusing on the study of the influence of the formation conditions and the wind speed of the frozen tunnel construction site on the frozen temperature field and stress field.This paper analyzes the temperature field of the soil layer during different thawing periods,the displacement and stress of the lining segment through the thermo-solid coupling analysis module of ANSYS software,and sets up a clay-soil layer,a sand-soil layer and a pebble-soil layer for comparative analysis.Studies have shown that soil properties have different effects on the displacement and stress of lining segments atdifferent positions.Among them,the thawing cycle and thawing sensitivity of the three types of soil have great differences,and the thawing of the soil body on the lining segments in the early stage of thawing the resulting displacement and stress changes more drastically.In this paper,the displacement and stress of the pipe segment lining structure were analyzed by setting the three wind speed conditions of 1m/s,5m /s and 10m/s.The study shows that: in the early stage of thawing,the displacement of pipe segment lining structure is highly sensitive to the low wind speed zone between 1m/s and 5m /s,while the stress of pipe segment lining structure is highly sensitive to the high wind speed zone between 5m /s and 10m/s.