Investigation of the Insulation Effect of Thermal Insulation Layer in the Seasonally Frozen Region Tunnel: A Case Study in the Zuomutai Tunnel, China

Table 1

Monthly and lowest daily mean air temperature and lowest temperature of the air and lining surface in the sections with thermal insulation layer in January 2017 and 2018.

Sections		Monthly mean air temperature (°C) (2017/2018)	Lowest daily mean air temperature (°C) (2017/2018)	Lowest air temperature (°C) (2017/2018)	Lowest temperature at lining surface (°C) (2017/2018)
K628 + 602	Vault	−5.4/−5.4	−8.3/−9.3	−15.2/−19.6	2.8/1.8
	Waist	−6.7/−6.7	−10.1/−10.5	−20.2/−22.8	2.0/1.2
	Side wall	−7.6/−7.8	−11.7/−12.8	−21.1/−25.7	—/—
K628 + 687	Vault	−4.7/−5.3	−7.5/−9.2	−13.2/−16.4	2.8/2.0
	Waist	−6.4/−6.4	−9.4/−10.5	−17.0/−20.3	2.3/1.2
	Side wall	−6.8/−6.9	−10.4/10.7	−18.3/−19.7	1.6/0.9
K628 + 900	Vault	−4.9/−5.1	−6.8/−9.2	−11.3/−13.4	3.0/2.1
	Waist	−5.8/−6.2	−8.0/−10.5	−15.0/−17.7	3.2/2.3
	Side wall	−6.2/−6.4	−8.6/−10.8	−15.1/−17.9	2.2/1.4
K630 + 690	Vault	−9.9/−11.5	−12.9/−18.1	−20.3/−24.3	—/—
	Waist	−11.7/−13.3	−15.9/−21.1	−22.2/−26.8	0.5/−1.6
	Side wall	−11.6/−13.4	−16.0/−21.2	−22.2/−27.0	−0.7/−3.3
K630 + 891	Vault	−9.6/−12.4	−13.1/−18.1	−20.2/−24.6	0.59/−1.9
	Waist	−11.4/−13.9	−16.8/−22.5	−23.1/−27.9	−0.4/−2.6
	Side wall	−12.8/−14.1	−18.3/−22.8	−24.4/−28.3	−1.2/−3.7
K631 + 090	Vault	−10.6/—	−15.1/—	−22.1/—	−0.3/—
	Waist	−12.1/—	−18.1/—	−24.5/—	—/—
	Side wall	−12.3/—	−18.2/—	−24.4/—	−3.7/—
K631 + 380	Vault	−12.7/−15.5	−18.9/−24.8	−26.1/−30.8	−2.0/−5.1
	Waist	−13.5/−16.3	−20.3/−27.1	−26.5/−32.0	−3.2/−5.0
	Side wall	−13.6/−16.3	−20.0/−26.8	−27.0/−31.6	−5.0/−5.2