Abstract:

In order to study the effects of rock thermal parameters difference caused by the change of multiphase components during rock mass phase transition on timespace laws of the surrounding rock temperature field, the thermal parameters formula of rock mass under different porosity is calculated. Based on the porous medium model, a temperature field calculation model considering phase change and thermal parameters with temperature dynamics is established. Taking latent heat into account, the change laws of space form at surrounding rock frozen fringe under different porosity and the influence of phase transition on temperature field are analyzed. The research results show that： (1) The higher the porosity of the saturated rock mass, the greater the influence on the overall thermal parameters of the rock mass. (2)When the surrounding rock is affected by low temperature, the frozen fringe moves deeper into the surrounding rock and gets wider, and the width is linear with its depth. (3)The porosity of saturated surrounding rock has great influence on the moving speed of the frozen fringe but has no effect on its width. (4)Due to the latent heat of phase change, the timehistory curve of the surrounding rock temperature during the freezingthawing cycle shows an asymmetrical steplike shape, and the step width is positively correlated with the porosity of the surrounding rock. (5)In the cycle of freezing and thawing, the difference existing in the frozen fringe adjacent to rock temperature gradient during heating and cooling can cause different thermal conductivity and directly leads to the asymmetry of the temperature history curve. (6) Along the radial direction of surrounding rock mass in chamber, amplitude attenuation and phase lag 〖HJ〗are existed in the temperature history function and the loaded temperature function in the surrounding rock mass, and the higher the porosity of the rock mass, the more obvious the phenomenon is.

Key words: tunnel in cold region, temperature field, phase transition, latent heat, porosity, frozen fringe, thermal conductivity, specific heat capacity