Investigation on Thawing of Cross Passage Based on Coupling Effect

Abstract:

Thawing of artificially frozen soil during and after the excavation of cross passage constructed by artificial ground freezing method isn’t well studied. Coupling the governing equations of temperature and stress, this paper investigates the issues of temperature field, development of frozen wall thickness, and thaw settlement considering the effects of convection and hydration heat from preliminary/secondary concrete lining. Cases of both naturally and artificially thawing are studied for the scenario of cross passage #1 in Shanghai Yangtze River Tunnel. In naturally thawing condition, it takes 44 days for all frozen soil to melt and this process is significantly influenced by the hydration heat from preliminary concrete lining while that only 23% of the frozen soil melt without regard to the hydration heat in 50 days. Soil mass in the cross passage area shows a downward displacement of 2cm due to the thawing effect. As for the case of artificial thawing, all frozen soil melts after 4.3 days. Contrary to the process of freezing, thawing of soil first occurs within the area between the two rings of freezing pipes, then that between the preliminary lining and the inner freezing pipe ring, and last that out of the outer ring.