The coupled moisture-heat process of a water-conveyance tunnel constructed by artificial ground freezing method

Artificial freezing ground method is widely applied in adverse geotechnical engineering conditions to improve the strength and reduce permeability of soil. It is a challenge to ascertain the progression of frozen wall and analyze the arrangement of freezing pipes due to the complexity of freezing process involving ice-water phase change and water migration. To analyze the progression of frozen wall and its influencing factors, a hydro-thermo coupling model is established, and a water-conveyance tunnel constructed by artificial freezing method is carried out. The results show that: (1) Water migration and ice-water phase transition have significant influences on temperature distribution, and their effects should not be neglected. (2) The thickness of frozen wall with temperature lower than 10 degrees C has attained the required design value at the end of active freezing. Meantime, under drive of temperature gradient, water migrates and redistributes. (3) The interval angle for two adjacent pipes is the main influencing factor on progression of frozen wall, followed by the freezing pipe diameter and horizontal spacing. Additionally, for coarse-grained soil, the influence of seepage on development of frozen wall is significant. This study will provide a theoretical reference for frozen wall design.