硬岩高效破裂是深部地下空间､深部资源勘探开发的重要前提,寻求和发展高效破岩技术成为大势所趋｡微波具有加热效率高､无二次污染等优点,被认为是一种极具发展潜力的高效辅助破岩技术｡微波场内岩石体破裂差异性行为解译是实践微波辅助破岩技术的重要基础｡从宏-细-微观不同尺度对微波场内砂岩､花岗岩和辉长岩开展了跨尺度破裂行为机理研究｡结果表明:在岩石宏观膨胀破裂层面,砂岩表现为低温崩裂破坏,实测最高温度为194 ℃,辉长岩和花岗岩则为高温熔融破坏,实测最高温度分别可达367 ℃和492 ℃;岩石脱离本身基质约束产生裂纹或宏观破裂面时体积变化明显,高温熔融破坏时岩石体积膨胀率最大,花岗岩和辉长岩破裂时体积膨胀率为2.1%和1.8%｡在岩石细观破裂面特征层面,微波场内高温熔融作用所产生的破裂面比低温崩裂面分维高2.0%,其中花岗岩､辉长岩和砂岩的破裂面分维分别为2.109 2,2.070 4 和2.066 0｡在岩石微观损伤差异性机制层面,岩石破裂特征与主要成岩矿物的组分､含量和含水率密切相关｡一方面,由于石英和其他矿物介电特性差异较大,当岩石内部石英含量较高时,热应力迅速增长;另一方面,水在微波作用下迅速汽化,在岩石内部产生高孔隙压力,试样易低温崩裂破坏,微观断口不会出现显著的损伤结构;而当岩石内部主要矿物组分介电特性差异较小及含水率较低时,试样内温度增长缓慢,矿物温度梯度相对较低,后期岩石整体呈现高温熔融破坏;岩石晶体化学分子结构分析结果发现,试样内部Si—O 键含量波动幅度较大,石英和硅酸盐矿物XRD 衍射峰和对应衍射角发生偏移,晶体主要受到微观压应力作用,表现为花岗岩的石英和斜长石矿物内部和交界处出现大量的显微裂纹和孔洞,辉长岩的损伤结构主要集中于辉石矿物内部,据此可推断适合微波辅助破岩的地质岩性工况,以期提高深部硬岩破岩效率｡

Efficient fracturing of hard rock is an essential prerequisite for exploring deep resources and developing deep underground space.The development of efficient rock-breaking technology has become a general trend.Microwave is considered as a highly efficient auxiliary rock-breaking technology with excellent development potential because of its high heating efficiency and freedom from secondary pollution.The interpretation of differential fracture behavior of rock samples under the microwave field is an essential basis for the practice of microwave-assisted rock-breaking technology.In this study, the cross-scale fracture behavior mechanisms of sandstone, granite, and gabbro under the microwave field based on macro-scale, meso-scale, and micro-scale were investigated.The results showed that at the macroscopic expansion fracture level of the rock, the sandstone exhibited a low-temperature collapse failure, and the maximum temperature was measured at 194 ℃, while gabbro and granite exhibited a high-temperature melting failure and the measured maximum temperatures could reach 367 ℃ and 492 ℃, respectively.The volume of the rock changed significantly when it broke away from its matrix to produce cracks or macroscopic fracture surfaces.The rock volume expansion rate was the largest when it was melted at high temperature, and the volume expansion rate of granite and gabbro reached 2.1% and 1.8% when they were broken.At the level of rock mesoscopic fracture surface characteristics, the value of the fractal dimensions of fracture surface caused by high-temperature melting in microwave field was 2.0% higher than that caused by low-temperature collapse failure.The fractal dimension values of the fracture surface of granite, gabbro and sandstone were 2.109 2, 2.070 4, and 2.066 0, respectively.In terms of the differential mechanism of rock microdamage, the fracture characteristics of the rock were closely related to the main components,rock-forming minerals content and the moisture content.On the one hand, when the quartz content in the rock was high, the thermal stress increased rapidly due to the significant difference in dielectric properties between quartz and other minerals.On the other hand, water vaporized rapidly under the microwave irradiation, resulting in high pore pressure in the rock, and the sample was prone to low-temperature collapse failure, where was no significant damage structure on the microfracture.However, when the difference in the dielectric properties of main mineral components in the rock was slight and the moisture content was minimal, the temperature inside the sample increased slowly.The temperature gradient of minerals was lower, and the whole rock showed a high-temperature melting failure in the later stage.A rock crystal chemistry and molecular structure analysis found that the content of the Si—O bond in the sample changed significantly, and the XRD diffraction peaks and corresponding diffraction angles of the quartz and silicate minerals shifted.The crystals were mainly affected by micro-compressive stress,showing a large number of microcracks or holes inside the quartz and plagioclase minerals of the granite and at the junction of two minerals.The damage structure in gabbro was mainly concentrated inside the pyroxene minerals.Therefore, the geological and lithologic conditions suitable for microwave-assisted rock breaking on this basis can be inferred to improve the rock-breaking efficiency of deep hard rock.

1 试样制备及实验方法设计

   1.1 试样制备

   1.2 试验设备和实验方案设计

2 微波场内岩石体破裂行为特征

   2.1 微波场内岩石宏观体破裂响应特征

   2.2 微波作用后岩石破裂面形貌特征

3 微波作用后岩石热膨胀响应特征分析

   3.1 微波作用下岩石异质热响应行为

   3.2 微波作用下岩石热膨胀特征

4 微波场内岩石破裂机制探索

   4.1 微波场内岩石破裂面断口特征分析

   4.2 岩石矿物分子结构微波响应特征分析

   4.3 微波作用下岩石物相特征变化分析

   4.4 微波场内岩石体破裂机理初探

5 结论与展望