Study on the weakening law of mechanical properties and damage constitutive model of pre-cracked cyan sandstone after freeze-thaw cycle

Abstract

Abstract Water-bearing fractured rock masses are prone to geological hazards due to freeze-thaw (FT) damage, which brings adverse effects on the stability of rock engineering. In order to study the FT damage characteristics of rocks, the intact and pre-cracked samples of cyan sandstone were taken as the research objects, with pre-crack inclination angles (β) of 0°, 45°, and 90°, respectively. The effects of FT cycle on stress-strain curve, peak strength, apparent stiffness and FT coefficient were investigated by uniaxial compression test after different times of FT damage treatment. Based on macro damage variables, a damage constitutive model of cyan sandstone is proposed by combining strain equivalence hypothesis and Weibull distribution hypothesis. Considering that the strain equivalent hypothesis is difficult to reflect the compaction effect of microfracture, the damage constitutive equation is modified with the ratio of the secant modulus of the actual stress-strain curve to that of the classical Lemaitre damage constitutive curve as the correction coefficient. The application results show that the modified constitutive model can well describe the stress-strain relationship of cyan sandstone before the peak strength, verify the reliability of the model parameters derived from the test data, and the practicability of the damage characterization method and correction coefficient. The results can provide theoretical reference for the study of FT damage of rocks in cold regions.