Study On Coupling Analysis Of Seepage,Temperature And Stress In The Cold Region Tunnels Under Group Hole

Along with the steady and rapid development of China's economy is the perfection of the traffic network.The railway and highway infrastructure in China's northwest and northeast and other places are booming.However,due to the mountainous areas,high altitude,low temperature and other reasons,there are many problems in the construction of road facilities.Tunnel engineering as one of the important links,its importance is self-evident.Based on the Dangjinshan Tunnel of Dunhuang-Geermu Railway,the seepage field,temperature field and stress field of tunnels in high altitude and cold region including main tunnel,horizontal guide tunnel and cold-proof drainage tunnel are separately and coupled in theoretical and numerical simulation in this paper.The main research work is as follows: The characteristics and changes of horizontal and vertical displacement and maximum and minimum principal stress of each tunnel chamber under single stress field before and after the main tunnel is lined;the characteristics and changes of pore water pressure of each tunnel chamber when it reaches stability under single seepage field;the characteristics and changes of maximum freezing depth of surrounding rock of each tunnel chamber under single temperature field;Characteristics and variations of horizontal and vertical displacements and maximum and minimum principal stresses of each tunnel chamber under temperature-stress coupling before and after the main tunnel is lined;Characteristics and variations of horizontal and vertical displacements and maximum and minimum principal stresses of each tunnel chamber under seepage-stress coupling before and after the main tunnel is lined;Characteristics and changes of maximum freezing depth of surrounding rock in each tunnel chamber under seepage-temperature coupling;The characteristics and changes of horizontal and vertical displacement,maximum and minimum principal stress and maximum freezing depth of each tunnel chamber under the coupling of seepage,temperature and stress.The conclusions are as follows:(1)The arch feet of the main tunnel,the arched waists of the main tunnels,and the left and right side walls of the cold-proof and leak-proof tunnels are heavily stressed;After lining,the tensile force of tunnel surrounding rock decreases and the pressure increases;(2)After the excavation of the tunnel,the stress distribution of surrounding rocks will be redistributed.The vaults of each cave will sink and the bottom will swell,and the subsidence of the vault will increase first and then trend with the extension of the excavation time.With stability,the amount of uplift at the bottom will first decrease and then stabilize,as the excavation time prolongs.At the same time,the amount of subsidence of the vault will increase with the decrease of the average monthly temperature,but the displacement of the uplift at the bottom will increase with the month.The decrease in average temperature has not changed much;(3)Under the action of temperature field,the maximum freezing depth of each cavern is on the vault,which increases with the decrease of monthly average temperature.The maximum freezing depth of the main tunnel under the coupling of seepage,temperature and stress fields is-10?,-15?,-20?and extreme-25?,-30?,-35C,respectively,is 1.20 m,1.50 m,1.74m,1.90 m,2.02 m and 2.13 m;(4)The maximum pore pressure of the main tunnel appears at the right arch foot,the maximum pore pressure of the horizontal guide of the tunnel appears at the left arch waist,and the pore pressure of the left and right side walls of the cold-proof water-discharge tunnel differs little,and the maximum pore pressure appears at the junction of the side walls and the bottom;(5)Compared with seepage field,temperature field has less influence on the vertical displacement field of each cavern.For example,the maximum settlement of the main tunnel without lining is-10?,-15?,-20?,-25?,-30? and-35?.The maximum settlement of the main tunnel is 8.33 mm,8.41 mm,8.48 mm,8.55 mm,8.63 mm,8.70 mm respectively,while the maximum settlement of the main tunnel is 12.41 mm when the seepage field is stable.The same stress field has little effect on the temperature field.The maximum freezing depth of each tunnel chamber under the coupling of temperature-seepage field and seepage field,temperature and stress field,has almost no change;(6)Under the coupling of seepage,temperature and stress,the tension of each tunnel chamber becomes serious with the decrease of the monthly average temperature of each tunnel,but the compression of each tunnel chamber decreases with the decrease of the average temperature;the monthly average temperature is-10?,-15?,-20?,-25?,-30? and-35? and the maximum settlement of the main tunnel is 4.51 mm,4.59 mm,4.68 mm and 4.68 mm,4.77 mm,4.85 mm and 4.95 mm,respectively.The maximum uplift volume does not change much about 4.16 mm;(7)On the basis of numerical simulation,it is predicted that the negative temperature of the lining of the main tunnel,the horizontal guide tunnel and the cold proof tunnel in the coldest month of the tunnel operation will occur in the 34 th,50th and 64 th years after the tunnel operation respectively.