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Thickness Calculation Method for the Insulation Layer of the Tunnel in Cold Region Considering Seepage and Fissures
(1. Yanqing-Chongli Expressway Preparatory Office of Hebei Expressway Group Limited, Zhangjiakou 075400; 2. Key Laboratory of Transportation Tunnel Engineering of the Ministry of Education, Southwest Jiaotong University, Chengdu 610031)
Abstract The impact of fissures and seepage on the temperature field of tunnels in cold regions cannot be neglect? ed. Based on the Qipanliang Extra-long Tunnel in the Hebei section of the Yanqing-Chongli Expressway, a random fissure model considering seepage was built and the impact of various factors on the depth of tunnel freezing was explored so as to establish the calculation equation of insulation layer thickness. The research results showed that (1) the negative temperature section at the inlet of the tunnel in the coldest month was 172 m long, and the negative temperature section at the minimum temperature was 273 m; the negative temperature section at the outlet in the coldest month was 238 m, and the negative temperature section at the minimum temperature was 292 m; anti-freezing shall focus on the range of 300 m in the inlet section. (2) The existence of fissures had a non-negligible impact on the distribution of temperature fields, and due to the influence of "separation" of fissures, the tunnel section envelopes were nonuniform, and the maximum depth of frost appeared at the crown. (3) The depth of frost was negatively correlated with porosity, permeability, specific heat capacity and initial temperature of surrounding rocks and was posi? tively correlated with heat conductivity coefficient and heat transfer coefficient. The sensitivity of the depth of frost to various factors was ranked as follows: initial ground temperature > specific heat capacity > porosity > heat conductivity coefficient > heat transfer coefficient > permeability. (4) In the established calculation equation of insulation layer thickness, the impact of fissures and seepage was considered to get the insulation layer thickness (4.2 cm) in the inlet section and the insulation layer thickness (4.8 cm) in the outlet section.
Abstract：
The impact of fissures and seepage on the temperature field of tunnels in cold regions cannot be neglect? ed. Based on the Qipanliang Extra-long Tunnel in the Hebei section of the Yanqing-Chongli Expressway, a random fissure model considering seepage was built and the impact of various factors on the depth of tunnel freezing was explored so as to establish the calculation equation of insulation layer thickness. The research results showed that (1) the negative temperature section at the inlet of the tunnel in the coldest month was 172 m long, and the negative temperature section at the minimum temperature was 273 m; the negative temperature section at the outlet in the coldest month was 238 m, and the negative temperature section at the minimum temperature was 292 m; anti-freezing shall focus on the range of 300 m in the inlet section. (2) The existence of fissures had a non-negligible impact on the distribution of temperature fields, and due to the influence of "separation" of fissures, the tunnel section envelopes were nonuniform, and the maximum depth of frost appeared at the crown. (3) The depth of frost was negatively correlated with porosity, permeability, specific heat capacity and initial temperature of surrounding rocks and was posi? tively correlated with heat conductivity coefficient and heat transfer coefficient. The sensitivity of the depth of frost to various factors was ranked as follows: initial ground temperature > specific heat capacity > porosity > heat conductivity coefficient > heat transfer coefficient > permeability. (4) In the established calculation equation of insulation layer thickness, the impact of fissures and seepage was considered to get the insulation layer thickness (4.2 cm) in the inlet section and the insulation layer thickness (4.8 cm) in the outlet section.
YU Jianyou1 JIANG Yifan2 LIN Ming2 LIU Jianqi1 CAI Libin2 JIANG Xinzheng2 WANG Zhijie2 ZHOU Ping2
.Thickness Calculation Method for the Insulation Layer of the Tunnel in Cold Region Considering Seepage and Fissures[J] MODERN TUNNELLING TECHNOLOGY, 2022,V59(4): 108-117
2022, Vol. 59 