Research on the Failure Mode and the Compression Strength for the Frozen Clay at Different Temperature Gradients

The triaxial compression tests are performed on the frozen clay under three thermal gradients by use of the GFC (freezing with thermal gradient, istropically consolidation)method. The failure modes under different thermal gradients and the weakening effects of thermal gradients and the confining pressure on the strength are investigated. The results indicate that: (1) The thermal gradients have significant influences on the failure modes of the frozen soil. However, the effects of the confining pressure can be ignored compared with the thermal gradients. The failure modes under different thermal gradients present bottom bursting characteristics, but show middle bursting characteristics in the homogenous thermal field. The non-uniform distribution laws for the radial expanding amplitude and the vertical compression amplitude are the main forms of the “inhomogenous effects”, which are enhanced as the thermal gradients increase. (2) The failure volumetric strain change to expansion from shrinking gradually accords with the increase of the thermal gradients (or the thermal increase) under different confining pressures. (3) The strength decreases as the thermal gradients increase at the same confining pressure , and that increases firstly then decreases as the confining pressure increases under different thermal gradients, the reason for which can be attributed to the ice thawing and the fissure extension. (4) The compression strength under different thermal gradients can be described by the modified linear yielding criteria set up in the homogenous thermal field.