Abstract: In order to predict heat storage capacity of shallow underground tunnels' surrounding rock, a transient heat transfer model of the rock under synergistic effects of periodic surface temperature and tunnel wind temperature was developed by adopting finite volume method. Then, a suitable factor-less quasi-discrete model was selected and a solution procedure was prepared. Distribution characteristics of dimensionless temperature field in surrounding rock at different Biot numbers and Fourier numbers were investigated, an unstable heat transfer quasi-nomogram of tunnel walls was drawn, and total heat storage for the rock in different annual cycles was assessed by checking the map. Finally, the model's was verified through case studies. The results show that dimensionless temperature within influence of double periodic temperature boundary fluctuates according to simple harmonic waves, while the overlying rock layer of the tunnel is more affected by superposition of double periodic temperature waves, whose temperature increases significantly in autumn. Moreover, as the surrounding rock generally exhibits heat storage during yearly cycle, its annual storage decreases slightly from year to year and eventually becomes stable.

Key words: subway tunnel surrounding rock, heat storage, periodic, ground temperature, airflow temperature