Effect of Wet-Dry Cycles on the Loading–Unloading Damage of Granite

Abstract

Investigating the effect of wet-dry (W-D) cycling on loading–unloading damage is crucial for ensuring the stability of granite slopes in mountainous areas prone to strong earthquakes. This study conducted a series of W-D cycling and loading–unloading tests on granite samples, complemented by weight measurements, wave velocity assessments, and nuclear magnetic resonance (NMR) tests on samples subjected to W-D cycling. The results indicated that W-D cycling reduced the mechanical properties of granite and increased the irreversible strain, dissipated energy, and number of acoustic emission (AE) counts during loading–unloading. The increase in the number of W-D cycles led to a significant rise in the number of small-scale, intergranular, and transgranular microcracks and the gradual formation of middle-scale and large-scale microcracks. W-D cycling weakened the granite because of crystal expansion and contraction as well as mineral dissolution, whereas loading–unloading damaged the granite through inconsistent deformation resulting from the varying hardness of different minerals. This study provides a foundation for understanding the formation mechanism of seismically cracked slopes under the combined effects of rainfall and earthquakes.