Quantifying Rock Fatigue and Decreasing Compressive and Tensile Strength after Repeated Freeze‐Thaw Cycles

Frost action is believed to control rock slope erosion in cold environments and is a major driver of rockfall generation. While other frost weathering by ice segregation has been proved effective in previous laboratory studies, we investigate the effects of volumetric expansion on samples of sandstone because it is the best‐constrained process for quantifying damage. We conducted up to 17 freeze‐thaw cycles using 26 identical sandstone cylinders and repeatedly measured porosity, elastic moduli and compressive and tensile strength in the laboratory. To analyse the damage mechanism, we monitored strain during single freeze‐thaw cycles. In contrast to previous studies, both partially (50%) and highly (90%) water‐saturated samples display significant deformation during freeze‐thaw cycles. This indicates that rapid freezing in a non‐uniformly sized pore space can cause damage if only a portion of the pores is fully saturated. Compressive and tensile strength of highly saturated samples decreases by approximately 40 per cent and 95 per cent, respectively, over 17 freeze‐thaw cycles. Porosity increases by 80 per cent after three cycles and only by another 30 per cent in the next 14 cycles, indicating rock fatigue by destruction of the grain bonds. We introduce a generalised fatigue damage model, capable of comparing fatigue damage under different weathering regimes and in different rock types. We show how repeated frost action systematically causes rock fatigue and a major decrease in compressive and tensile strength of rocks. Copyright © 2015 John Wiley & Sons, Ltd.