Simulation Of A Thermo-hydro-mechanical Coupling In Metro Connected Aisle By Artificial Freezing Method

With the development and utilization of urban underground space resources,the number of tunnels and subways projects has been increasing;especially the construction of subway construction has become the main means to solve the urban congestion.In this paper,the construction method of artificial freezing method of Zhengzhou Metro Line 1 Longzihu Central Station ~ Wenyuan North Road Station ~ Henan University Station is taken as an example.Using the comprehensive method of indoor frozen soil mechanics experiment,numerical simulation and field measurement,the variation law of the temperature field,seepage field and stress field of the formation during the freezing process and the distribution of the displacement field are systematically studied.The main contents are as follows:(1)the typical sand in Zhengzhou region for the first time of frozen soil under uniaxial compression and uniaxial bending and triaxial shear test,study under different soil,temperature,moisture content and confining pressure strength characteristics of sandy soil in Zhengzhou area.(2)Based on the theory of continuum mechanics、thermodynamics and seepage mechanics,the three-field coupling mechanism control equation of temperature field,seepage field and stress field is established by using Drucker-Prager criterion and matching Mohr-Coulomb criterion.(3)Using COMSOL Multiphysics finite-element software,considering the influence of temperature and unfrozen water content on the physical,mechanical and thermal physical parameters and variables,simulating the whole process of the freezing process of Zhengzhou Metro Line 1 about temperature field,seepage field and stress field.The distribution of temperature,seepage and stress during the freezing process and the settlement of the formation are simulated;the effects of different contact passage on the surface subsidence(the distance from the top of the passage to the surface 5m,10 m,15m and 20m);the effects of different soils(sand,silty clay and clay)on surface subsidence after excavation with a depth of 10 m were simulated.(4)In the process of subway contact passage construction,the monitoring of salt water temperature,frozen soil temperature and ground subsidence is carried out,and the monitoring results are analyzed reasonably.It can judge whether the formation state of freezing wall is good and its effective thickness,and make corresponding recommendations for similar engineering reference.(5)The numerical simulation data and the field monitoring data can reflect the change of the surface in different periods.It can be reasonable to determine the numerical simulation of the three field coupling of the temperature field,seepage field and stress field established in this paper is reasonable,the change of temperature,seepage and stress in numerical simulation can provide an effective theoretical basis for predicting the change of permafrost temperature and surface displacement during field construction.