Development of the borehole television system using the fluorescent technique

由于岩石中的微裂纹与其它材料的微裂纹没有明显的特征差异，用常规的钻孔电视系统识别微裂纹是非常困难的。为此，将目前广泛应用于显微镜下微裂纹和孔隙检测的荧光技术应用于钻孔电视系统中，设计了一种新型的圆形紫外灯，用于观察钻孔内部的微裂纹。在实验室环境中，在紫外光下发现了许多常规钻孔电视无法识别的隐藏微裂纹。荧光法进行灌浆过程的可视化。利用钻孔电视系统，在紫外光下可清楚地观察到含有荧光物质的各种灌浆混合物的分布。对兵库县舞古隧道加宽引起的岩体松动区进行了评价，并对九州横竹大坝边墙隧道的灌浆机理进行了分析。扩大隧道后，观察到新的微裂纹的形成和/或钻孔内的微裂纹的进展。利用该系统在紫外光下可清晰地观察到三种不同颜色的水泥浆充填的许多微裂纹，从而得出结论：结合荧光技术的钻孔电视系统已研制成功，对识别孔内微裂纹或含荧光物质的水泥浆是非常有用的。

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.