关键词: 冻胀力, 裂隙扩展, 弹性模量, 冻融循环, 塑性特征

Abstract: A brittle material such as rock deteriorates when subjected to freezing and thawing, it is generally observed that water phase transition due to temperature changing is the main reason of rock deterioration. Hydraulic pressure is generated by 9% volume increase of freezing water in closed crack. The pressure makes the crack expand and when the temperature rises, water moves to new cracks. The repeated cycles create new damage of rock. The freezing and thawing process of rock is also affected by a number of factors such as length of cracks, permeability, and heaving stress. The relationship between frost heave stress and crack extension length of a single fracture is established based on elastoplastic mechanics and fracture mechanics. Combined the equation of relationship between ice pressure and microcrack propagation length, the initial damage compliance tensor of the rock under the different freezing-thawing cycles can be calculated. According to the distribution of microcracks, the strain of rock induced by freezing-thawing can be decomposed into the initial damage strain, additional damage strain and plastic damage strain; and an elastoplastic damage model for rock under different number of freezing-thawing cycles is developed based on frictional sliding of pre-existing microcracks in this work. In the damage model, the plastic yield criterion of Drucker–Prager yield criterion is used simultaneously with the micromechanics damage model to simulate the inelastic deformation of rocks and Voyiadjis’ strain hardening function under compression; and it is used to define plastic behaviors of such materials. The calculated results show, the crack propagation length increases nonlinearly with increasing the crack and the compressive strength under different cycles of freezing and thawing. Finally, the applicability of the model is validated by freezing-thawing experiment, it is shown that the developed model can simulate the stress-strain curves under different of freeze-thaw cycles better.

Key words: heaving stress, crack expansion, elastic modulus, freezing-thawing cycles, plasticity