Abstract: To determine the freezing starting time of the combination reinforcement of the metro jet system(MJS) and horizontal freezing method, the hydration heatrelease law of a MJSreinforced cementsoil test pile is studied. The hydration heat and hydration heatrelease rate of the cementsoil pile with different cement contents (40%, 45%, 50%, 60%, and 70%) are measured using a direct method. Finally, numerical simulations are performed to predict the variation law of the MJS reinforcement temperature field using the data obtained from the hydration heat laboratory tests. A comparative analysis of the simulated prediction and the measured temperature of the MJS test pile from the field is performed. The results reveal the following. (1)The central temperature of the MJS cementsoil test pile increases with the increasing of cementmixing ratio. (2) The change trends of the simulated and measured temperatures of the test pile are similar, validating the numerical simulation. (3) The central temperature of the MJS cementsoil test pile first increases and then decreases gradually; the hydration heatrelease peaks in approximately five days, reaching 56.1~69.2 ℃. Thus, the hydration heat release of the cementsoil pile increases with the increasing of cementmixing ratio. (4) The temperature at the center of the large volume of the cementsoil pile increases due to the hydration effect. The hydration heat release of the MJS cementsoil test pile stops 30 days after construction, indicating that  artificial freezing reinforcement can be conducted.

Key words:  , metro jet system reinforcement, test pile, hydration heat, temperature field, cement soil, artificial freezing reinforcement