Abstract

Microwave technology is increasingly used in laboratory tests and field applications as an effective rock breaking technique. The underlying mechanism of rock fracturing induced by microwave energy, however, has not been well addressed. In this study, we employ experimental and numerical methods to investigate the global and local damage of rock in microwave radiation direction, including the fracture formation process. Our analysis focuses on three damage indicators under microwave irradiation, namely P-wave velocity attenuation, temperature distribution and fracture pattern. For a diabase sample, our experimental results indicate that the microwave power and irradiation time has a substantial influence on these three indicators. With increasing power level and irradiation time, we measured a lower P-wave velocity, higher temperature, and more fractures within the rock substrate. We observed that under the same energy, heating at higher power levels for shorter durations has a better weakening effect. Our numerical results show that thermal stress mismatch in the local high-temperature area is the main reason for crack initialization. Nucleation and propagation of microcracks depend on the thermal stress induced by global temperature increase, the geometry of the sample and existing fractures.

摘要

微波技术作为一种有效的破岩技术越来越多地用于实验室测试和现场应用中。然而，由微波能量引起的岩石破裂的潜在机理尚未得到很好的解决。在这项研究中，我们采用实验和数值方法研究岩石在微波辐射方向上的整体和局部损伤，包括裂缝形成过程。我们的分析集中在微波辐射下的三个损伤指标，即纵波速度衰减，温度分布和断裂模式。对于辉绿岩样品，我们的实验结果表明，微波功率和辐照时间对这三个指标具有重大影响。随着功率水平和辐照时间的增加，我们测量到较低的P波速度，较高的温度，岩石基底内还有更多的裂缝。我们观察到，在相同的能量下，以较高的功率水平加热较短的持续时间会具有较好的减弱效果。我们的数值结果表明，局部高温区域的热应力失配是裂纹初始化的主要原因。微裂纹的成核和扩展取决于整体温度升高，样品的几何形状和现有裂缝所引起的热应力。