Abstract: The microwave treatment effect of rocks is affected by many factors. Among them, water is a good absorbing medium, and it can improve the microwave absorbing ability of rocks. This study aims at exploring the effect of saturation on response characteristics of rock subjected to microwave irradiation. Tests of 3 kW power microwave irradiation were carried out on basalt samples with different saturations to examine the variations of the heating characteristics, wave speed, porosity change as well as dynamic tensile strength. The test data was analyzed from the meso and macro perspectives. Some findings identified. 1) The water affects the heating characteristics of the rock sample during microwave irradiation. Within the first 15 s of irradiation, the group with saturation lower than 75% obviously promotes the heating rate; when the saturation reaches 100%, the effect is opposite, and the heating rate is lower than that of the dry group；within 15−30 s, the heating rate of the water-containing sample decreases with the decrease of water content and the endothermic heat of evaporation; within 30−45 s, the water evaporation is completed, the heating rate of the water-bearing sample is close to that of the dry sample. 2) The difference in water saturation leads to varying degrees of wave velocity and porosity changes in basalt after microwave irradiation. The wave velocity reduction range is 8.18%−17%, and the porosity growth range is 18.71%−43.65%. The damage effect does not follow the saturation. 3) Under the same irradiation conditions, the 50% saturation group quickly reaches the strength limit under the combined action of steam pressure and thermal stress, and the samples are directly damaged. Obvious mesoscopic damage are not be observed in most of the other groups of samples, and the difference in final dynamic tensile strength is not distinct.

Key words: microwave irradiation(MI), water-bearing rock, nuclear magnetic resonance (NMR), dynamic tension