Research On Reasonable Waterproof And Drainage And Thermal Insulation Measures For Tunnel Entrance Of Cold Region

With the construction of more and more tunnels in cold regions,the problem of frost damage has also received more attention.The tunnel opening is the throat of the tunnel.It is affected by rain,snow,wind and temperature changes all year round.Based on the seasonal frozen soil railway tunnel Alataoshan Tunnel,this paper carried out the research on the temperature field change rule,water drainage and thermal insulation measures of the tunnel section in winter.The main results are as follows:(1)Atmospheric temperature monitoring was performed to analyze the change law and determine the temperature boundary function for numerical simulation.At the same time,the temperature of different sections in the construction tunnel in winter was monitored to evaluate the effect of the cold insulation door and the heater.(2)Select the DIK4 + 345 section 55 m away from the tunnel exit,use the ANSYS finite element software to establish a two-dimensional model,use the control variable method to comparatively analyze the surrounding rock temperature field with and without insulation,and adopt different insulation materials and different insulation The laying method and the insulation effect at different insulation layer thicknesses show that the insulation effect is significant after the insulation layer is adopted,which can effectively reduce the freezing damage of the lining and the freezing of the drainage pipe,and provide reference value for a reasonable insulation layer design.(3)In order to study the surrounding rock temperature field distribution of the tunnel entrance section during the operation period,according to the actual engineering terrain,a three-dimensional model was established using Fluent software to simulate the air temperature field under the influence of different wind speeds and different external temperatures.Radial temperature changes can provide recommendations for the length of tunnel insulation.The DIK4 + 345 section(buried depth of 10m)and DIK3 + 905 section(buried depth of 30m)were selected to study the frost heave stress of surrounding rock and lining based on thermal-mechanical coupling.At the same time,the frost heaving stress of surrounding rock and lining was studied based on the thermo-mechanical coupling.The results show that the maximum tensile stress and the maximum compressive stress of the lining section are increased compared to those without frost heave.At the junction of the wall and the inverted arch,the maximum tensile stress of the 10 m shallow buried section increased more than that of the 30 m buried section.(4)Based on the field construction of the Alatau Mountain Tunnel,the reasonable drainage forms and key construction techniques of the tunnel inside and outside of the tunnel section were studied.In view of the complexity of the alpine region,it was proposed to focus on the concrete’s waterproof ability and to meet the impermeability level and thickness.And strictly guarantee the construction quality,consider using high-performance concrete.Secondly,in terms of the buried depth and thermal insulation layer of the central deep buried ditch,considering that the excavation section of the deep buried ditch in the center of a single-track railway tunnel is small,if the excavation depth is too large,it will cause some disturbance to the surrounding rock at the foot of the tunnel,leading to surrounding rock.The characteristics of poor integrity,it is recommended to appropriately reduce the burial depth and set up a thermal insulation layer.