Numerical Analysis of Temperature Field of Vertical Frozen Soil Wall Reinforcement at Shield Shaft

Abstract

For using vertical frozen working method as the reinforcement method at shield shaft, determination of the region of reinforcement, technology, as well as the evolution and distribution of temperature field of frozen soil curtain is the key problem. Aiming at shield launching project of Nanjing subway route-10 river tunnel, this paper applies finite element software to investigate the time series and distribution of temperature field. Nummerical results show that under the disigned frozen plan, the formation time of delivered circles in frozen wall, i.e., the required time for closing vertical frozen soil wall, is 7 days. After 30 days from frozen, vertical frozen forms a frozen soil wall of pressure load bearing for stopping water, with the thickness larger than 1.6m. Temperature in the area between frozen pipes at row B and tunnel face is lower than-26.67°C after 30 days from frozen. The distance between 0°C and-10°C isotherms and tunnel face is approximately 1.8m and 1.6m, respectively. 40 days after frozen, temperature in the area between frozen pipes at row B and tunnel face is still-26.67°C, but with larger area. The distance between tunnel face and 0°C and-10°C isotherms is approximately 2.1m and 1.8m, respectively. The numerical results provide theoretical data for future engineering designs that are simliar to the present study.