Application of reverse drilling rig method in the excavation of the vertical shaft of the outlet tunnel of the Huangjinxia Water Conservancy Project

The vertical shaft of the outlet tunnel of the Huangjinxia Water Conservancy Project has the characteristics of relatively complex geology, large excavation diameter, and deep vertical shaft depth. Therefore, the application of ordinary manual reverse excavation of the vertical shaft will impose immense difficulty on the progress and safety of the construction. After conducting rigorous pilot study, the reverse drilling method was selected for the excavation of the vertical shaft of the outlet tunnel, ensuring the success of the construction with great efficiency, speed and safety. Taking the successful application of the reverse drilling rig method in the excavation of the vertical shaft of the Huangjinxia Water Conservancy Project—Han-To-Wei Water Diversion project of Shaanxi Province as an example, the construction process and methods of the reverse drilling rig method were summarized. The prevention and treatment of pilot shaft blockage, safety measures were expounded, especially during the construction process, the successful construction technology and experience were achieved by adopting technical over-excavation, pilot shaft blockage prevention and treatment measures, providing useful construction experience and technical reference for similar projects in the future.