The Model Test Study on Frost Heaving and Melting Sedimentation of Subway Tunnel Construction with Manual Level Freezing Method

Abstract

With the aim of solving technical problems existing in the rehabilitation construction of butt-joint sect works with manual level freezing undermining method, under Huangpu River of Shanghai Underground Subway 4# between Nanpu Bridge station and Pudong South Road Station, Group of large-scaled physical model tests had been performed adopting the Manual Level Freezing Undermining Method (MLFM in brief) in constructing double track tunnel. Firstly, the model design and test system integration were made; afterward, through model tests, the paper systematically studied the laws of stratum frost heaving, melting sedimentation rule and stratum displacement variations etc, during the undermining construction of tunnel being frozen. The results indicate: the Maximum displacement of frost heaving measured at the top of freezing wall during up line freezing process was 1.36mm, which is equivalent to actual work quantity of 29.92mm; the strata melting sedimentation displacement during forceful thawing is 54% less than what was during natural thawing, which illuminates that adopting forcing thawing can reduce melting sedimentation of soil blocks.