The mechanical properties of high-pressure frozen ice are critical design parameters for deep artificial ground freezing and ice sheet drilling operations, making their investigation fundamentally significant. In this study, ice specimens were prepared at −10 °C under freezing pressures of 10, 20, 30, 40, and 50 MPa. In situ axial loading simulation experiments were conducted to investigate their mechanical behavior and macroscopic deformation characteristics during failure. The experimental results indicate that the deviatoric stress–axial strain curves of the ice specimens exhibited a rapid yet smooth transition before and after reaching the peak deviatoric stress, with all samples exhibiting ductile failure. The peak deviatoric stress initially increased and then decreased with increasing freezing pressure, reaching a maximum value of 8.61 MPa at a critical transition pressure of 20 MPa, eventually declining to a minimum of 1.66 MPa at 50 MPa. The residual deviatoric stress decreased significantly with increasing freezing pressure, declining from approximately 3.5 MPa at 10 MPa to 0.85 MPa at 50 MPa. The peak tangent modulus demonstrated a fluctuating trend with increasing freezing pressure, ranging from 1.76 to 2.37 GPa. As the freezing pressure increased, the failed ice specimens transitioned from a densely cross-cracked state to a highly transparent phase, and finally to a sparsely cross-cracked morphology.

The mechanical response and failure behavior of high-pressure frozen ice are essential to the technological progress in drilling thick polar ice sheets, but current research primarily focuses on non-pressure-frozen ice. In this paper, ice specimens with a cylindrical geometry were fabricated at −20 °C, applying freezing pressures across a range of 10 to 40 MPa with a 10 MPa interval. Their mechanical properties were investigated through triaxial compression tests under axial loading conditions and were compared with the results obtained at −10 °C. The results indicate that, with increasing freezing pressure, the samples transitioned from a failure state of interlaced cracking to a highly transparent state. The failure behavior observed in the specimens was characterized as ductile, as evidenced by the deviatoric stress–axial strain relationships. Moreover, the peak deviatoric stress exhibited a non-monotonic dependence on freezing pressure, with an initial rise from 9.59 MPa at 10 MPa to a peak of 14.37 MPa at 30 MPa and a subsequent decline to 10.12 MPa at 40 MPa. All specimens reached a relatively stable residual state at 5% axial strain, with residual deviatoric stresses ranging from 4.13 to 5.71 MPa. A reduction in freezing temperature from −10 °C to −20 °C can effectively enhance both the peak deviatoric stress and the residual stress of high-pressure frozen ice under triaxial shear conditions. All peak tangent modulus values, ranging from 1.61 to 2.93 GPa with an average of 2.2 GPa, were observed within 0.7% axial strain and exhibited mild fluctuations with increasing freezing pressure. These findings provide a more robust mechanical foundation for drilling research and operations in extremely thick polar ice caps.