Energy tunnel

which is based on ground source heat pump system

is one of the green

economical and efficient geothermal heat exchange techniques. It can integrate both the anti-freezing and heat preservation for tunnel. Based on the Yinchuan-to-Xi′an high-speed railway tunnel located in loess region

the heat exchange tubes are placed in series in the tunnel invert

and the ground source heat pump system has been built. The heating system is operated under different input powers as well as the inlet and outlet temperature

and the temperature and stresses of the inverted arch are measured. The thermal response characteristics of the tunnel under difference input powers are discussed and analyzed

including heat transfer capacity and thermal induced stresses

etc. Under this field test condition

the results show that the temperature of the inverted arch of tunnel has increased by 4.2℃ and 7.1℃ under 0.5 kW and 1.0 kW input power

respectively. With the increase of water temperature

the invert temperature increases slightly in a short period of time. When the heat propagation path has stabilized

the invert temperature finally presents a linear relationship. The increment of axial stress of the inverted arch of tunnel is larger than that of the longitudinal stress. The axial stresses are 1.15 and 1.29 times of longitudinal stresses under 0.5 kW and 1.0 kW input power

respectively.