Radial Thermal Gradient–Dependent Deformation Behaviors of Frozen Hollow Cylinder

The in-situ lateral temperature around freezing pipes in an artificially frozen shaft lining (FSL) is always nonuniform. In order to obtain a better understanding of the radial thermal gradient–dependent deformation behaviors of frozen soils, a test apparatus for a frozen hollow cylinder (FHC) under a radial thermal gradient and the matching specimen preparation device were developed. The results obtained showed that the temperature precision was within $\pm 0.05°\mathrm{C}$ and the measured thermal gradient fluctuation was within $\pm 0.03°\mathrm{C}/\mathrm{cm}$ by circulating refrigerants rapidly through the confined cells. The initiation and growth of the thermal gradient significantly lowered the elastic modulus and the peak strength but had little effect on the strain-softening behavior. The inclination angle of the observed shear band exhibited a slight increase as the thermal gradient increased. Further, a linear response was detected between the heterogeneity level and the peak strength, and it was independent of soil types and temperatures. These observations were fundamentally distinguished from previous studies on frozen soil specimens under a vertical thermal gradient and contributed to developing a practical technique to decrease the temperatures at the inner surface and thermal gradient near the inner surface of the FSL.