Coupling Analysis Of Water,Heat And Force In The Cold Area Tunnel And Its Reliability

With the continuous development of the western development strategy in recent years,the scale of highway and railway construction in the western alpine region has been expanding.During the construction of highway and railway engineering in the cold area,a large number of tunnel projects tunneling projects were built.However,in the process of engineering operation,there were various problems of frost damage.In this paper,the mechanism of frost damage is analyzed,and the physical and mechanical properties of the surrounding rock in the cold zone are studied.The coupling equations of water,heat and force are deduced.Based on the Highway tunnel of Bahadaban,a mathematical model of water,heat and force is established.The temperature field,stress field and deformation field of the tunnel are simulated for 50 years after the completion of the tunnel.The deformation reliability of the tunnel project is calculated and analyzed and failure probability.The main contents include:(1)Induction and analysis of the cold zone tunnel in the cold area,the main manifestations are as follows: leakage of the tunnel lining in the summer,the silting of the foundation with mud,the hanging of the tunnel in winter and the frost heave uplift of the foundation.(2)The mechanism of frost damage of tunnel lining structure is analyzed.The basic cause of the freezing damage in the cold area tunnel is that the moisture inside the tunnel rock mass has a frost heave force on the rock mass and the tunnel lining when the temperature falls below the freezing point of the water.(3)The basic theory of temperature field,seepage field and stress field coupling is summarized and analyzed,the coupling equations of temperature field,seepage field and stress field are established.(4)The mathematical model of temperature field,seepage field and stress field coupling is established with the background of Bahadaban tunnel.The variation of temperature field,stress field and deformation field in 50 years after tunnel construction is simulated and analyzed.The results show that:(1)In the temperature field,the temperature of the secondary lining is 5.26 ℃ when the tunnel is not laid in the 50 th year after the completion of the tunnel.In the laying of the insulation layer,the temperature of the secondary lining of the tunnel is only 1.64 ℃And the depth of melting of the tunnel rock is 2.0m when the insulation layer is not laid.When the insulation layer is laid,the depth of melting is 1.1m.It can be seen that the 5 ℃ thick insulation layer has obvious effect on the tunnel cooling effect.(2)the maximum tensile stress at the bottom of the arch is 0.32 MPa and the maximum compressive stress of the vault is 4.12 MPa.At the end of the tunnel,the maximum tensile stress at the bottom of the arch is 1.36 MPa,The maximum compressive stress of the vault is 5.67 MPa.It can be seen that the maximum tensile stress of the lining at the bottom of the tunnel has a great influence on the stability of the tunnel in the 50 th year after the completion of the tunnel.(3)deformation field: the completion of the construction of the Bahadaban tunnel,the tunnel dome vertical downward displacement of 2.07 mm,vertical arch vertical upward displacement of 5.39mm;tunnel in the first 50 years in January,vertical crown displacement is 6.30 mm,invert the vertical displacement is 9.32 mm,the end of the tunnel construction,the level of the displacement of tunnel sidewall is 2.98 mm,and the horizontal displacement of the tunnel side wall in the 50 th year of the tunnel is 6.59 mm at the end of the tunnel construction.(5)Based on the analysis of the temperature field,stress field and deformation field of the Bahadaban tunnel,the response surface method and the check point method are used and the corresponding calculation program is written to calculate the reliability index and the reliability index Failure probability.The results show that the reliability index of the tunnel is 4.5052 and the failure probability of the tunnel is 0.0016% at the end of the construction of the Bahadaban tunnel when the allowable deformation is 8mm.The reliability index of the tunnel is decreasing with the time,The failure probability of the tunnel is increasing,and the growth rate is gradually increasing.The deformation reliability index of the 50 th year after the completion of the Bahadaban tunnel is 1.9736 and the corresponding failure probability is 5.6900%.