Development of the borehole television system using the fluorescent technique

由于微裂缝与岩石的其他材料没有特征差异，因此用常规的井眼电视系统识别微裂缝是非常困难的。因此，我们将荧光技术应用于井眼电视系统的显微微裂缝和孔隙空间的检测。设计了一种新型圆形紫外灯，用于观察钻孔内微裂纹。在实验室环境下，在紫外线下发现了许多传统井眼电视无法识别的隐藏微裂缝。采用荧光法对注浆过程进行了可视化。利用钻孔电视系统，在紫外光照射下清晰地观察了含荧光物质的各种浆液混合物的分布。进行了兵库县迈科隧道扩宽引起的岩体松动带评价和九州横武坝边坡隧道注浆机理分析两项现场试验。在隧道加宽后，观察到钻孔内新微裂纹的形成和/或微裂纹的发展。利用该系统，在紫外光下可以清晰地观察到由三种不同着色物质混合的浆液填充的微裂缝。结果表明，与荧光技术相结合的钻孔电视系统是一种成功的技术，可用于识别孔内含有荧光物质的微裂缝或浆液。

It is very difficult to identify microcracks using conventional borehole television systems, because there are no characteristic differences in microcracks from other materials of rocks. Therefore, we applied the fluorescent technique, which is widely used to examine microcracks and pore spaces under a microscope for the borehole television system.A new circular ultraviolet lamp was designed to observe microcracks inside boreholes. Many hidden microcracks that were not recognized by a conventional borehole television were disclosed under ultraviolet light, in the laboratory setting. The fluorescent approach was performed for visualization of grouting processes. The distributions of various grout mixtures containing fluorescent substances were clearly visualized under ultraviolet light, using a borehole television system.Two field tests, evaluation of a loosened zone in a rock mass caused by widening of the Maiko Tunnel in Hyogo prefecture and analysis of grouting mechanisms in the limb tunnel of Yokotake Dam in Kyushu, were carried out. Formation of new microcracks and/or progression of microcracks inside boreholes were observed after widening of the tunnels. Many microcracks filled with grout mixed with three different coloring substances were clearly visualized under ultraviolet light using this system.It is concluded that the borehole television system combined with the fluorescent technique has been successfully developed and is very useful for identification of microcracks or grout containing fluorescent substances inside horeholes.