Effects of microwave radiation on the anisotropy of heat transfer and mechanical properties of layered rocks

• The anisotropic characteristic of wave speed and thermal conductivity would be enhanced with that of tensile strength experiencing a increasing and decreasing profile. • 2.The interlayer stress is closely related to the differences of temperature and temperature gradient. The former term leads to the interlayer shear stress with later term causing the interlayer compressive/tensile stress. • Thermal stress causes the bedding plane fracturing, incrcasing the thermal resistance of the bedding plane and subsequently changing the temperature distribution on both sides of the bedding plane and the temperature gradient in the vertical bedding direction. Layered rock is frequently seen in rock-breaking engineering practice. However, the effect of microwave radiation on the mechanical behavior and thermal property anisotropy of layered rock is not well understood. In this paper, microwave radiation experiments were carried out on layered rocks with different bedding angles. The microstructure, mineral compositions, thermo-mechanical properties, as well as the relationship between anisotropy and microwave radiation time were studied. The mechanism of interlaminar cracking under microwave irradiation was analyzed, and the evolution of interlaminar stress was revealed. Results show that the failure mode of rock and the temperature field are extensively related to structural characteristics. The surface temperature field and fracture mode of the sample after microwave irradiation show obvious layered distribution characteristics because of the layered distribution of minerals. The interlaminar stresses mainly include the bedding-parallel shear stresses and bedding-perpendicular tensile/compressive stresses. The interlayer stress is caused by the expansion mismatch between the adjacent rock layers parallel to and the bending deflection perpendicular to the bedding direction. A larger temperature increment and difference contribute to greater shear stresses parallel to the bedding direction. Similarly, an increased temperature gradient resulted in more significant tensile/compressive stresses perpendicular to the bedding direction. Considering the present findings, the application of microwave rock-breaking technology to layered rocks with microwave-absorbing minerals has greater advantages.