Group Effect of Freezing Pipes in Sand Layers Subjected to Saltwater Seepage

Groundwater seepage affects the formation of a frozen curtain during artificial ground freezing (AGF) in the sand layer. A thermal–hydraulic–chemical–mechanical (THCM) coupling model is derived in this paper to analyze phase change, heat and mass transfer, and frost heave during AGF. The accuracy of the proposed THCM model is verified by applying it to examine the laboratory model tests presented in the literature. The groundwater seepage heavily weakens the range of frozen soil on the upstream side of the freeze pipes. The average degree of AGF at a given time is defined as the percentage of the pore volume filled by ice and crystals to the total pore volume in the target area. The higher the seepage velocity and the larger the spacing of freeze pipes, the slower the procedure to fully form a frozen curtain. For a seepage velocity of 10 m/day, the time factor to achieve 100% of the average degree of AGF using double rows of freeze pipes installed with a spacing of 1.0 m is 34.6% shorter than that of a single-row configuration with the same spacing.