Abstract: Consolidated and drained triaxial shear tests were conducted on Yanji swelling rock to investigate the effects of wetting-drying, freezing-thawing and wetting-drying-freezing-thawing cycles on the stress-strain behaviour, volumetric strain and shear strength of Yanji swelling rock samples. The test results indicate that the stress-strain behaviour of samples before cyclic treatments appears to be strain-hardening, while the samples after cyclic treatments show strain-softening behaviour and more evident shear dilation. Additionally, the effects induced by cyclic treatments are more pronounced with increasing number of cycles and decreasing confining pressure. As the number of cycles increases, the cohesion of samples significantly decrease but the internal friction angle slightly increases. It can also be seen that the samples subjected to wetting-drying-freezing-thawing cycles suffer greater alterations in mechanical properties compared with those subject to separate wetting-drying and freezing-thawing cycles. Subsequently, a stress-strain formula considering the effect of wetting-drying-freezing-thawing cycles and confining pressure is presented based on Konder hyperbolic function, which can describe both strain-hardening and strain-softening behaviours. A comparison between the predicted and measured values verifies that this model can well predict aforementioned stress-strain behaviours.

Key words: swelling rock, wetting-drying-freezing-thawing cycle, stress-strain behaviour, shear strength, normalization