| The tunneling frost heave in the cold region has always been the focus of experts and scholars.In this paper,the stress and deformation characteristics of the tunnel entrance section in the cold region,especially the tunnel portal position,are studied through the combination of indoor model test and numerical simulation analysis.First,make sure the overall temperature distribution of tunnel entrance section model,by placing sensors to measure model at tunnel entrance section and the characteristics of bearing force and deformation rules,using numerical simulation method for simulating model,and finally compare the indoor model test and numerical simulation results concluded that cold regions tunnel burrows in the axial stress distribution,so as to provide reference for practical engineering.In order to achieve the above objectives,this paper mainly carried out the following specific work:(1)indoor freezing-thawing model test of tunnel entrance section model in cold region:according to the similarity theory and with reference to the actual tunnel and the actual seasonal frozen soil climate conditions,the experiment design is carried out after corresponding simplification.Indoor model test as a carrier of the test model,with large refrigeration equipment,according to test the related properties of the remoulded sample design experiment,the two kinds of conditions in the process of test design three tests in the face of the temperature,strain,respectively,set up relevant measure points,after David wall stress measuring point measuring axial frost heaving force,set on the slope and David set displacement measuring point,data acquisition instrument is used to analyse the whole process of the model test data collection.The results show that in terms of temperature field,the higher the moisture content is,the faster the cooling rate will be when the temperature is above zero.In terms of portal stress,the areas with greater axial stress at the portal are mainly concentrated in the one-week range close to the lining,and the corresponding positions of the arch waist,side wall and invert in the one-week range of the lining have greater corresponding stresses.In terms of displacement,through the monitoring of the displacement at the portal during the experiment,it is found that the displacement at the portal is generally uniform,and the displacement will decrease in the middle part of the slope above the portal.The influence of water content on displacement is mainly manifested as the trend that the greater the water content is,the greater the displacement will be.(2)finite element numerical simulation research based on indoor model test: based on the experimental conditions of indoor model test,the finite element analysis software ANSYS is used to analyze the experimental model under two working conditions.After selecting the model parameters according to the experimental data,the temperature field of the model is calculated.Then the results of temperature field are extracted and coupled indirectly as thecondition of stress field analysis to realize the coupling of temperature and stress fields.The results show that the temperature field of the model is evenly distributed,and the temperature change is stable and continuous.When the temperature is above zero,the higher the moisture content is,the faster the temperature drops.The axial stress distribution at the portal was mainly concentrated in the week close to the lining.The stress at the lining arch,the left and right sides of the lining and the lining invert were relatively large,and with the increase of moisture content,the position of the stress in the lining would move inward and outward within a certain range. |
