Study On Temperature Field And Frost Heave Force Of Chaoyang Tunnel In Seasonal Frozen Regions

With the rapid development of Chinese economy,the highway network in Northeast China is becoming more and more perfect.In the process of constructing the expressway,the tunnel plays an important role in the mountainous terrain conditions.Due to the cold winter weather in the northeastern region,the water in the surrounding rock of the tunnel,the water temperature in the surrounding rock decreases and the water-ice phase changes,causing the surrounding rock to freeze and expand.Under the constraints of unfrozen surrounding rock and lining.At this time,the lining will withstand the frost heaving force generated by the deformation of the surrounding rock,resulting in a series of freezing damage,threatening the safety of the vehicle and people,and hindering the normal operation of the traffic.Therefore,it is very necessary to study and prevent the freezing damage mechanism of the tunnel in the seasonal frozen regions.Through the study of the tunnels with freezing damage in the seasonal frozen regions,it is shown that the temperature field distribution of the surrounding rock and the frost heave force caused by the frost heave of the surrounding rock are the main reasons affecting the tunnel freezing damage;this paper takes the Chaoyang of the Heda Expressway in the seasonal frozen regions.The tunnel is a supporting project.The indoor field,on-site monitoring,theoretical analysis and numerical simulation are used to study the temperature field and frost heave force.The parameters are determined by on-site monitoring and laboratory tests.The numerical simulation of the distribution of the surrounding rock temperature field in the Chaoyang tunnel is carried out.The freezing depth parameter is provided for the calculation of frost heave force.The distribution law and influencing factors of frost heave force are studied by elastic mechanical theory calculation and thermal-structural indirect coupling numerical simulation method.The temperature field and frost heave force are studied.Provide corresponding preventive measures for tunnel freezing damage.The main conclusions are as follows:The thermal conductivity increases first and then decreases with the increase of moisture content of granitic gneiss;the thermal conductivity of granitic gneiss in natural water state is within a certain temperature range(-15 °C~20 °C),with The decrease in temperature first increases and then decreases;In the process of frost heaving of granitic gneiss,from room temperature to-40 °C,the frost heaving deformation of granitic gneiss is mainly divided into three stages: cold shrinking stage,frost heaving stage and freezing.Reducing the stage and determining the frost heave rate of the granitic gneiss is 0.045%;The large-scale finite element simulation software is used to simulate the surrounding rock temperature field of Chaoyang Tunnel,and the distribution law of surrounding rock temperature is consistent with the law obtained by on-site monitoring.The maximum frozen depth of the three sections of the Chaoyang Tunnel is 2.5m(30m from the hole),2.0m(60m from the hole),1.5m(90m from the hole);The thickness of the insulation layer is different,and the insulation effect of the surrounding rock temperature field of the Chaoyang tunnel is different.The thickness of the same insulation layer,the farther the tunnel hole section is from the hole,the better the insulation effect of the surrounding rock.Therefore,in the antifreeze measures of the tunnel,it is recommended to lay a thick insulation layer in the hole section;According to the monitoring of the surrounding rock fissures of the Chaoyang Tunnel and the frost heaving experiment of the granitic gneiss,the frost heave rate of the surrounding rock of the Chaoyang Tunnel(the surrounding rock at 60 m from the entrance)is 0.6%;According to the elastic theory,the frost heave force of the three sections of the tunnel is 0.85 MPa for section one(30 m from the hole),0.76 MPa for section 2(60 m from the hole),and 0.67 MPa for section 3(90 m from the hole).It can be seen at the tunnel entrance.Segment,with the increase of longitudinal depth,the frost heave force decreases;the frost heave force of the lining increases with the freezing depth,frost heave rate and lining thickness of the surrounding rock,and then the freezing depth and frost heaving rate are frozen.The influence of the expansion force is large,and the increase of the thickness of the lining has little effect on the frost heave force.Under different working conditions,the influence of the freezing depth and the frost heave rate on the value of the frost heaving force is basically consistent with the elastic theory calculation.The maximum value of the frost heaving compressive stress of the lining is mainly distributed on the inner side of the lining arch;the frost heaving compressive stress on the outer side of the lining arch is also large.Therefore,in the antifreeze measures of the tunnel,it is recommended to take corresponding protective measures for the tunnel arch and the arch waist.