Field Observations on Influence of Inclined Shaft on Temperature Characteristics within an Extra-long Tunnel in Cold Regions
Research purposes:Temperature distribution in cold region tunnels is the key of thermal insulation design and frost damage prevention.Factors affecting the temperature distribution in cold region tunnels can be summarized into three categories as meteorological environment,engineering structures and traffic factors.Compared with factors related to meteorological environment and traffic,there are few studies focusing on the influence of engineering factors on the temperature distribution characteristics,especially ventilation facilities of long and extra-long tunnels.Taking an extra-long highway tunnel in the southeast margin of the Qinghai-Tibet Plateau as example,the meteorological environment of the construction site and the spatial distribution and seasonal variations of air temperature along the tunnel during the construction process were observed continuously.The influence of inclined shaft on the temperature distribution along the tunnel was discussed based on the field-observed data.Research conclusions:(1)Before the tunnel was break through,the ventilation was poor,the influence distance of outside air temperature on the air temperature within the tunnel was 300～400 m from the portal.The annual average and amplitude of air temperature within the entrance section increased and decreased exponentially,respectively,with the increase in the distance from the entrance.(2)After the tunnel was dug to the inclined shaft and connected between each other,a stable one-way ventilation was developed from the entrance to the inclined shaft in cold season due to chimney effect of the shaft.Then,the air temperature in the tunnel presented a linear distribution and the temperature gradient was about 0.5 ℃/100 m.(3)After the tunnel was break through,chimney effect of the inclined shaft led to a stable two-way ventilation from the inlet and outlet to the inclined ventilation shaft in cold season.The temperature in the tunnel presented a symmetrical distribution with the inclined shaft as the axis of symmetry,and significant negative temperature appeared within the tunnel.(4)The inclined shaft had a considerable influence on the temperature distribution and the frost penetration within the tunnel,and should be taken into account in the design of thermal insulation and frost damage prevention.
cold regions tunnelinclined ventilation shafttemperature distributionchimney effectfield observations
NETL
NSTL
万方数据
