Field Tests of the Horizontal Freezing Method for Shield Tunneling in Complex Sites

Abstract

To study the freezing characteristics and the effects of the horizontal freezing method of shield tunneling on the surrounding environment at a complex site, a systematic study with field measurements of the temperature and frost heave displacement fields of horizontal cup-type freezing was conducted on the south end shield tunneling of the Shuanghehu station of Zhengzhou metro line 17. The conclusions of the current research are: (1) the soil has a greater effect on freezing than the average moisture content of the soil layer. On the premise of a similar average moisture content, silt continues to cool at a faster rate after reaching the freezing point; (2) within the outer circle of the freezing tube, the rate of expansion of the freezing curtain decreases with distance from the freezing tube. The rates of development measured by the outer holes of the left and right line tests are 2.40 and 6.03 times those of the inner holes, respectively; (3) frost heave displacements are larger near the frozen area. The maximum frost heave in the frozen area is about 1.60–1.83 times that in the unfrozen area; (4) the temperature measurement holes in the left line fell below 0 °C 6 days later than the right line. The flow of groundwater has an adverse effect on the effect of freezing consolidation.