Abstract: According to the similarity criterion, the freezing model tests were carried out on Beijing sand-gravel stratum to study the expansion rule of the temperature field of the multi-row-pipe partial horizontal freezing body under the effect of seepage. Three factors were mainly investigated, including the length of water surface, downstream flow length, and thickness of the multi-row-pipe partial horizontal freezing body. The results show: 1) the temperature in the central part of the horizontal freezing body develops fastest and is the lowest, while the temperature in the upper part develops slowest and is the highest. 2) Percolation gradually makes the columns of the permafrost lap in the upstream direction from the downstream face to the upstream face. Moreover, the upstream and downstream temperature fields are no longer symmetrical. In the late stage of freezing, the back surface is in the shape of a sloping roof. 3) The effect of seepage on the horizontal frozen body progressively increases with the increase of seepage velocity. During the active freezing period, the freezing front expansion velocity of the last frozen soil column and the average development speed of the horizontal freezing body in the upstream direction are both in a squared and negatively correlated relationship with the seepage velocity. When the seepage velocity exceeds 14.1 m/d, the frozen soil column does not overlap, which is the limit flow rate of the model test. According to the theory of equivalent trapezoidal algorithm, the development of the horizontal freezing body can be easily evaluated by the average temperature formula of the multi-row-pipe partial horizontal freezing body under seepage. The research results can provide the basis for the basin-shaped freezing construction of large-flow velocity stratum.

Key words: multi-row freeze-tubes, percolation, temperature field, average temperature formula