Abstract: The temperature of freezing refrigerant is a key factor affecting the frost heaving force of upper structure undercrossed by tunnel. Hence, in order to quantitatively study the effect of increasing refrigerant temperature on reducing the frost heave of soil, the tunnel of Shanghai Metro Line No. 18 crossing underneath the station of Line No. 10 is taken as an example, and the temperature field and stress field of soil under the freezing temperatures of -18 ℃ and -28 ℃ are studied by laboratory experiments and similar simulation experiments. The sample test is a closed oneway freezing test, and the results show that the peak of frost heave pressure generated by the freezing of -18 ℃ refrigerant is 52.9% smaller than that of -28 ℃ refrigerant, and the rising rate of frost heave pressure is 20.1% lower. The similar simulation experiments are based on a similar law to calculate parameters such as station size, frozen pipeline diameter and the refrigerant flow, and it is concluded that the frost heave peak of -18 ℃ refrigerant is 20% lower than that of -28 ℃ refrigerant, and the raising rate of the frost heave pressure is 58% lower. The results of two groups of experiment show that the model of -18 ℃ refrigerant freezing can reduce the increasing rate and peak value of frost heave pressure effectively, and the frost heave pressure generated under lateral restraint conditions is larger than that generated in the similar simulation model test. The experimental results can provide a technical reference and data supporting for frost heaving sensitive and major risk projects.

Key words: artificial ground freezing method, refrigerant temperature, metro tunnel, frost heaving pressure, similar simulation experiment